3.1 The Schedule File

The schedule file is the main, and perhaps only, input file that the user prepares. It provides bookkeeping information for telescope and correlator operators, points to the desired catalogs or contains segments of catalogs, gives overall control commands to describe the observations and lays out the detailed sequence of observing scans.

A large number of input parameters are available for the schedule file. They are all described in detail in this section. However, most of the parameters default to reasonable values for ordinary VLBI observations and can be ignored by most users. The easiest way to determine which ones to worry about is to follow one of the examples and consult the detailed descriptions only when unsure of the meaning or behavior of a parameter.

The descriptions of the parameters for the schedule file, and later for the setup files, contain a wealth of information about VLBI systems and scheduling style. Serious users might find it instructive to browse through these sections.

This section starts with list of the parameters, with one line per parameter and, for web users, a link. When a parameter is given as mixed upper and lower case, the lower case letters are optional in the input file. The main part of this section is the detailed descriptions of every parameter. These descriptions start with some text describing the parameter, its actions, and information about how to use it. Every parameter description ends with a short table giving the following information:

Argument: The data type expected.

Options: A list of specific options if appropriate.

Default: The value assigned by SCHED if the parameter is not given in the schedule file.

Usage: Can the parameter be specified for each scan or only once? If for each scan, what happens if it is specified for one scan and not the next.

Example: An example specification of the parameter.

If a parameter for which SCHED only wants one value is specified for more than one scan, only the last value will be used. For parameters that can be specified for each scan, nearly all default to the value for the previous scan if not specified. The only exceptions are START, STOP, REP, GROUP, POINT, and COMMENT. Normal defaulting for these parameters would produce undesirable behavior. Note that TAPE, REWIND, FASTFOR, REVERSE, are not obsolete because they were specific to tape, which is no longer in use.

3.1.1 Summary List of SCHED Parameters

COVER INFORMATION:

VERSION:  Schedule version number. Helps identify latest.

EXPT:     Short description of project.

EXPCODE:  Project code.

PINAME:   Name of Principal Investigator.

ADDRESS1: Principal Investigator’s address for cover

ADDRESS2: information. Up to 4 lines allowed.

ADDRESS3:  

ADDRESS4:  

PHONE:    Principal Investigator’s phone number.

OBSPHONE: Principal Investigator’s telephone number during obs.

TELEX:    Principal Investigator’s TELEX number (obsolete).

EMAIL:    Principal Investigator’s electronic mail address(s).

FAX:      Principal Investigator’s FAX number.

OBSMODE:  Frequency band, recording system etc.

OBSTYPE:  Type of observation. Mostly for recorder control

NOTE1:    1st of 4 comment lines for cover information.

NOTE2:    2nd of 4 comment lines for cover information.

NOTE3:    3rd of 4 comment lines for cover information.

NOTE4:    4th of 4 comment lines for cover information.

COVERLET: Flag that in-line cover letter follows.

CORRELATOR INFORMATION:

CORREL:   Correlator to be used. Destination for recordings and log files.

CORAVG:   Correlator average time.

CORAVG2:  Alternate correlator average time.

CORCHAN:  Number of spectral channels per baseband channel.

CORNANT:  Number of antennas to be correlated.

CORPOL:   Polarization processing on or off.

CORSRCS:  Origin of source positions for correlator.

CORWTFN:  Correlator weighting function.

CORTAPE:  Type of media on which to send correlator output to user.

CORDFMT:  Format of export data.

CORSHIP1: Shipping address for correlator output.

CORSHIP2:

CORSHIP3:

CORSHIP4:

CORNOTE1: Notes for correlator operations.

CORNOTE2:

CORNOTE3:

CORNOTE4:

PROGRAM CONTROL:

DEBUG:    Turn on various debugging printouts.

OVERRIDE: Flag for programmers to bypass restrictions.

DOSTA:    Restrict processing to specific stations.

DOVEX:    Write a VEX file.

VEXTEST:  Allow use of unreleased VEX features.

EXIT:     Finish interactive input.

OVERwrit: Overwrite files from previous run of SCHED.

PLOT:     Invoke plotting part of SCHED.

SCHedule: Name of file containing rest of schedule.

FREQLIST: Write some information from the frequency file to frequencies.list and quit.

NOSETUP:  Do not use a setup. For planning schedules.

CATALOGS and other other “external” input.

LINEINIT: Following inputs will be rest frequencies.

SETINIT:  Name and flag for in-line setup data.

SRCCAT:   Flag for start of in-line source catalog.

SRCFILE:  Name of external source file.

SRCFILE2: Name of second external source file.

STACAT:   Flag for start of in-line station catalog.

STAFILE:  Name of external station file.

LOCFILE:  Name of locations file.

TAPEFILE: File name for tape initialization information.

TAPEINI:  Flag that next group of input is tape initialization.

EPHFILE:  File containing JPL ephemeris data for planets.

FREQFILE: File containing standard frequency setups.

PEAKFILE: File with reference pointing parameters.

PEAKINIT: Following inputs are for reference pointing.

PCENTERS: Flag for start of lists of multiple phase centers

GENERAL CONTROL PARAMETERS:

CALTIME:  Integration time for calibration data.

DODOWN:   Keep down antennas in scans.

DOSCANS:  Keep only this scan range. Mainly for operations.

WRAP24:   Double a 24 hour schedule to allow different start.

IATUTC:   IAT-UTC for planetary motion cards at VLA.

INTENTs:  Directives for observing, correlation, and processing.

LINEPG:   Number of lines per page in operator schedules.

LST:      Schedule is in LST for specified station.

NCHAN:    Number of baseband channels (Obsolete - set in setups).

PRECDATE: “Observe” date for coordinate conversions.

SUMITEM:  Items to show in the summary file.

TANTSTA1: List 1 of stations for Ta measurement requests.

TANTSTA2: List 2 of stations for Ta measurement requests.

BASIC SCAN TIMING and CONFIGURATION:

STATions: Station list for scan. Up to 30.

SOURCE:   Source name.

QUAL:     Qualifier for source.

YEAR:     Year of first scan stop time.

MONTH:    Month number.

DAY:      Day number. 1 is first day of MONTH. Can be day of year.

START:    Start time of scan.

STOP:     Stop time of scan.

DURation: Duration of scan.

DWELL:    Duration of scan but start when antennas on source.

GAP:      Minimum interval between scans.

PRESCAN:  Time to wait before starting recording (Obsolete).

PRESTART: Time to start recording before scan start.

PREEMPT:  Protect scan from preemption at PT and MK for EOP observations.

GROUP:    Number of scans to repeat.

REPeat:   Number of times to repeat scan(s).

SETUP:    Name of file containing VLBA setup information.

COMMENT:  Comment to appear in schedule.

SCANTAG:  Name for scan to put in summary tables.

SCAN PROPERTIES:

LINENAME: Name of group of rest frequencies to use.

DOPINCR:  Minimum increments for frequency setting.

DOPPLER:  Set frequency based on velocity for spectral line.

NODOP:    Turn off Doppler calculations.

DOMKA:    Record on Mark5A during Mark5C observations.

DOPCAL:   Obsolete form of DOPPLER.

DOPSRC:   Set frequency based on velocity of this source.

FREQ:     Up to 16 baseband channel sky frequencies for VLBA.

BW:       Baseband channel bandwidths.

CRDCH1:   First main channel for related VLBA legacy channel.

CRDNCH:   Number of VLBA legacy system channels.

CRDFREQ:  Force VLBA legacy BBC frequencies separate from RDBE.

CRDBW:    Force VLBA legacy BBC bandwidth separate from RDBE.

CRDDOP:   Provoke Doppler setting of VLBA legacy BBCs separate from RDBE.

CRDNODOP: End Doppler setting of VLBA legacy BBCs separate from RDBE.

CRDSETCH: List of setup baseband channels to use on VLBA legacy system.

PCAL:     Mode for pulse cal generators.

CENTERS:  Use multiple phase centers in processing.

PEAK:     Peak up on source.

NOPEAK:   Turn off peak up request.

POINT:    Convert the scan to a reference pointing scan.

PKWATCH:  Extra output when AUTOPEAK selected.

TANT1:    Turn on Ta measurement at the TANTSTA1 stations.

TANT2:    Turn on Ta measurement at the TANTSTA2 stations.

TSYS:     Turn on Tsys measurements (obsolete)

NOTSYS:   Do not measure system temperature (obsolete)

GEOSEG:   Insert a geodetic (DELZN) segment.

GEOSRCS:  Gives a list of sources for geodetic segments.

GEOPRT:   Turn on debugging print from geodetic insertion.

GEOTRIES: Number of trial geodetic segments to test.

GEOBACK:  Number of look-back scans while selecting geodetic segment sources.

GEOSLEW:  Relative weight of slew time in selecting geodetic segment sources.

GEOSLOW:  Stations getting to source this much later than others can be left out of a scan in a geodetic sequence.

GEOSREP:  Minimum number of scans between repeats of the same source in a geodetic sequence.

GEOLOWEL: Upper boundary of “low” elevation region for geo sources.

GEOHIEL:  Lower boundary of “high” elevation region for geo sources.

PN3DB:    Do VLBA half power tracking tests.

NOPN3DB:  Turn off VLBA tracking tests.

PTVLBA:   Do VLBA pointing sequence.

NOPTVLBA: Turn off VLBA pointing measurements.

TAVLBA:   Request Tant measuring mode.

NOTAVLBA: Turn off VLBA antenna temperature measurements.

PTDUR:    Duration of each step in VLBA pointing sequence.

PTSLEW:   Time to allow for slewing to source in pointing sequence.

AZCOLIM:  Azimuth collimation offset for scan for VLBA.

ELCOLIM:  Elevation collimation offset for scan for VLBA.

FOCUS:    Focus offset for scan for VLBA.

ROTATION: Subreflector rotation offset for scan for VLBA.

ROTPAT:   Expand pointing patterns to include focus/rotation.

ROTOFF:   Rotation offsets for ROTPAT pattern.

FOCOFF:   Focus offsets for ROTPAT pattern.

CRDLINE:  Arbitrary line for VLBA files for on-line testing.

RECORDER CONTROL

MINPAUSE: Minimum record stop time between scans.

RECord:   Record this scan. Non-zero or NOREC to not record.

NORECord: Do not record this scan.

The following parameters are obsolete as they only applied only to tape.

AUTOTAPE: Request automatic tape changes. Give tape time.

FASTFOR:  Fast forward the wide band tape.

REWIND:   Rewind wide band tape.

REVERSE:  Reverse direction of recording of wide band tape.

TAPE:     Force a tape change. Reset AUTOTAPE reference time.

TPREF:    Reference time for Mark II tape changes.

TAPESYNC: Synchronize tape changes (see warnings).

eVLBI CONTROL:

DATAPATH: Controls where data goes first.

GRABTO: Controls where recorded data goes.

GRABTIME: Controls which data are sent.

GRABGAP: Controls how much time is needed to send data.

OPTIMIZATION (Beware — experimental features!):

OPDUR:    Duration for experimental optimizing mode.

OPELPRIO: Two elevation ranges in which OPSKIP not active.

OPMINEL:  Minimum elevation for an ”up” source.

OPMINANT: Minimum number of antennas in a scan.

OPMISS:   For OPTMODE = SCANS, only keep this scan if this many scans have been skipped.

OPNOSUB:  Don’t subarray in experimental optimizing mode.

OPSKIP:   Skip source OPSKIP times unless in priority elevation range.

OPTLOWT:  Time scale for low el samples in OPTMODE = CELLS or CSUB.

OPTMODE:  Optimization mode.

OPPRTLEV: Print level for optimizing routine (mainly mode HAS).

OPTSLEW:  Time scale for slews in OPTMODE = CELLS or CSUB.

OPHA:     Prefered hour angle for scan OPTMODE=HAS.

OPHAWID:  Tolerance for hour angle OPTMODE=HAS.

OPHAWT:   Importance of HA vs other weights OPTMODE=HAS.

OPHASTA:  Reference station for hour angles OPTMODE=HAS.

OPMINSEP: Minimum separation of scans on a source OPTMODE=HAS.

OPSLEWWT: Importance of slew time vs other weights OPTMODE=HAS.

OPSLEWTI: Scale time for slew time weights OPTMODE=HAS.

OPHLIMWT: Importance of near limits vs other weights OPTMODE=HAS.

OPHLIMTI: Importance of HA vs other weights OPTMODE=HAS.

OPHMAXDT: Maximum offset from desired HA to consider OPTMODE=HAS.

HIGROUP:  Group a few scans from which to choose one based on El.

AUTOPEAK: Insert reference pointing scans.

MAPLIM:   Lat/long limits for station map when OBSTYPE=CONFIG

GRIDNR:   Number of radial cells in uv optimization grid.

GRIDNT:   Number of azimuthal cells in uv optimization grid.

GRIDMIN:  Inner radius of uv optimization grid.

GRIDMAX:  Outer radius of uv optimization grid.

GRIDW0:   Characteristic radius for linear to logarithmic grid spacing.

GRIDSTEP: Set the spacing of points for quality grid around a station.

GRIDMEAS: Set which quality measure to use.

GRIDVLA:  Specify that only baselines to VLA antennas are to be used.

UVMFS:    Show effect of MFS in UV plots.

SPECIAL VLA PARAMETERS:

VLAINTEG: VLA correlator integration time.

VLAPTIME: Duration of phasing subscans on the EVLA

VLAMODE:  VLA observing mode.

VLAPEAK:  Control reference pointing.

VLANTSYS: Turn off VLA system temperature corrections.

VLAPSRC:  Phasing source for VLA observations.

VLARFANT: Reference antenna for single dish or phasing.

VLATSYS:  Turn on VLA system temperature corrections. Also VLANTSYS.

VLATYPE:  Type of VLA observations.

VLAUSERN: Obsolete - VLA user number.

3.1.2 Details of SCHED Parameters

ADDRESS1, ADDRESS2, ADDRESS3 and ADDRESS4

ADDRESS1, ADDRESS2, ADDRESS3, and ADDRESS4 are used to give the Principal Investigator’s address for the cover information. At least the first line must be provided if recording.

Argument: A character string of up to 64 characters for each of the 4 parameters.

Options: Any.

Default: Blank

Usage: Only one value used, the last.

Example: ADDRESS1=’1003 Lopezville Rd’

ADDRESS2=’Socorro, NM 87801

ADDRESS3=’ U S A

AUTOPEAK

AUTOPEAK, without an argument, is used to request automatic insertion of reference pointing scans based in information in the PEAKFILE (which can also be specified in the schedule input file using PEAKINIT). See the section on reference pointing for much more information. Note that specifying AUTOPEAK will cause SCHED to try to insert pointing scans, but does not guarantee that it will find scans at high enough frequency or with enough of a gap from the previous scan. Scans will be inserted when it has been at least 10 minutes since the last set of pointing measurements and when there is adequate time for one or two pointing patterns based on the dwell time in the PEAKFILE. This can be triggered by specifying specifying adequate gaps using GAP. In such circumstances, the pointing will be inserted during the specified gap. The minimum interval between the original scans will maintain the interval from GAP, but the pointing will be inserted during that time. The interval between the inserted pointing scans and the input scan will typically end up much less than GAP.

Argument: No argument. Just specifying it turns on the attempts to insert scans.

Options: None

Default: Not set. Will not attempt to insert scans.

Usage: If set anywhere in the schedule, scan insertion is turned on.

Example: AUTOPEAK

AUTOTAPE

AUTOTAPE is an obsolete parameter that only applied to tape. It can be ignored by users of disk-based recording systems (eg Mark5) and eVLBI.

AUTOTAPE is used to request that automatic tape allocation and control be used at stations that use the VLBA control system and have more than one tape drive. It has no effect on other stations such as those that use VEX or on VLBA controlled stations with only one tape drive. AUTOTAPE=1 or AUTOTAPE=2 causes the on-line system to determine the tape direction, head position and track allocation automatically. The schedules will only include instructions on whether to run, stop, or rewind. AUTOTAPE>=2 also activates automatic reversal of the tapes when the low tape mark is reached, even in the middle of scans; with AUTOTAPE=1 the tape will stop at the low tape point and wait for the next scan. The default action (any other value of AUTOTAPE including no value) is to have SCHED determine the tape motion and related information.

Automatic tape allocation is now required for most VLBA observations. AUTOTAPE=2 should therefore be specified in most schedules. AUTOTAPE=1 is risky and probably should not be used. It is provided only so that SCHED can create schedules for all modes that the on-line systems can handle.

Automatic tape allocation cannot be used for projects that will not be correlated on the VLBA correlator. SCHED will refuse to make such schedules. This relates to how the correlators learn how the tape was handled at the stations. Non-VLBA correlators generally obtain some of the tape positioning information from the schedules rather than the logs, and, with automatic allocation, the two can be very different.

When automatic tape allocation is specified (AUTOTAPE=2), any station that is using the automatic allocation will be removed from a scan if the source is below the hardware limits at both ends of the scan. One can tell when this happened because a “D” will appear next to the --- in the summary file elevation and azimuth for a scan where this happened. There is no override. If one is need, let Craig Walker know and it can be added. This function will mainly affect the Mauna Kea VLBA site which is often scheduled in scans before the source rises and which has long access times for the site techs doing tape changes.

For more information on how automatic tape handling works, see the AUTOMATIC TAPE ALLOCATION section.

The rest of this section concerns the use of AUTOTAPE for the Mark II system. It can be ignored by most (all?) current users.

For Mark II, AUTOTAPE requests automatic tape changes. Without it, tape changes must be explicitly specified. The value specified for AUTOTAPE, if there is one, should be a time. The default, if no argument is given, is 4:00:00, which is the recommended value. Specify a negative number to turn off tape changes and a positive number (a time) to change the default tape length. Tape changes are requested at intervals of the requested time beginning with the earliest start time of the whole schedule. If this would require a change in the middle of a scan, the change is moved to the start of the scan and all following changes are moved up. This is station dependent and so can cause non-simultaneous tape changes. The tape is assumed to be kept moving between scans.

The reference time for AUTOTAPE (Mark II use) can be altered with TPREF in the SCHED keyin file and with the TPTIME in the TAPEFILE. See Section 3.4 for information on TPTIME. TPREF is a time of the form hh:mm:ss. The automatic tape changes are requested at integral numbers of 4 hour intervals (for the recommended time) before or after TPREF. A date is not needed because 4 hours divides 24 hours evenly. Even if someone were to use the 2 or 6 hour VCR modes, those tape lengths still divide 24 hours evenly.

If TAPE is specified in a Mark II schedule for a scan while AUTOTAPE is set, a tape change will be requested and following tape changes will occur at 4 hour intervals from the time of the forced change. One specification of TAPE is usually all that is needed to get the tape changing sequence right if the earliest start time is a poor reference time.

For most Mark II projects, the default action of AUTOTAPE should be good. The major exceptions are projects that start on the half hour and tape changes are desired on the hour, and projects where it makes sense to have a short tape at the start on some stations to avoid short tape on other stations for which the source rises later. Both of these cases can be handled nicely with TPREF.

Note that for Mark II observations, if AUTOTAPE is turned off, no initial tape mount at the start of the project will be requested. This causes problems at some stations. It you insist on specifying all tape changes with TAPE, be sure to put one on the first scan for each station. This mode of setting tape changes is NOT recommended.

Argument: None or a number.

Options: Mark III or VLBA: Not 1 or 2 - SCHED sets tape direction, head position, and track assignments. =1 - VLBA on-line systems set above parameters. =2 - activate mid-scan automatic tape reversals. Mark II: No argument or 0 - do automatic tape changes at 4-hour intervals. -1 - turn off automatic tape changes. hh:mm:ss - time for modified tape length.

Default: Mark III or VLBA: SCHED controls tape.

Mark II: AUTOTAPE=4:00:00

Usage: Only one value used, the last.

Example: AUTOTAPE=2

AZCOLIM

AZCOLIM can be used to specify an increment to the azimuth collimation offset value used for pointing. This is added to the nominal position known by the on-line system for the particular receiver and to the value specified in the setup file. It is also added to the values used for offsets in pointing patterns and the value from the setup file.

Argument: An azimuth collimation offset in arc minutes.

Options: Any value.

Default: 0.0

Usage: Default to previous scan.

Example: AZCOLIM = 0.25

BW

BW specifies the bandwidths to use for the scan. One value can be given for each baseband channel. Any unset values will be set equal to the first so it is usually only necessary to specify one. Because of details of how the defaulting works, once more than one channel is explicitly set to a non-zero value (rather than just defaulting to the first), be sure to set that channel explicitly again, or it will retain the previous value. To get back to the default, explicitly set the bandwidth to zero. Note that, once upon a time, the sign of the bandwidth indicated the sideband, but that is no longer true.

Some (all?) of the digital backend systems, including the RDBE, cannot oversample. Plus the software job in SCHED to allow the sample rate to track the input bandwidth is looking a bit serious - the sample rate gets entangled with disk management etc. So, at least for now (written in Dec 2013), it will be necessary to make a new setup file to use a different bandwidth for most observations.

Note that new parameter CRDBW can be used to set the VLBA legacy system BBCs to a bandwidth when using the RDBE, which, with the PFB personality, cannot be set to narrow bandwidths. This is useful for reference pointing. Since the legacy system can oversample, CRDBW can be used without a new setup file.

Argument: Up to one real number for each channel. The number is the bandwidth in MHz.

Options: Need valid setting for the backend in use. For the VLBA legacy system, they were 0.0625, 0.125, 0.250, 0.5, 1, 2, 4, 8, or 16 MHz. For the digital backends, must be half the sample rate.

Default: Uses bandwidth from setup file.

Usage: Uses the most recent value specified.

Example: BW=2,2,2,2

CALTIME

CALTIME is the integration time in seconds for calibration data from the VLBA monitor system. This includes the total and switched powers used for system temperatures and also the pulse cals.

This is currently ignored for PCFS (VEX) systems.

Argument: A time in seconds for each scan.

Options: Any.

Default: 120

Usage: Uses the most recent value given.

Example: CALTIME=60

CENTERS

Triggers the use of multiple phase center processing on the DiFX correlator at least at the VLBA. In practice, this puts the list of phase centers in the .v2d file used in setting up correlation. Some day, it may put the list in the .vex file, if there is a standard for how to do that.

The argument of CENTERS must correspond to a list of names in the phase center groups listed after a PCENTERS command.

For now, there is no clear way to make the phase center list scan dependent, so specify the same name for each scan on the same source. This may not always be true, which is why the association of a phase center group with a pointing source is not done in the PCENTERS specifications.

For more information on multiple phase center processing, see that section about that topic.

Argument: A name of a group of phase centers. For now, must be the same for every scan on a given source.

Options: Any name of a group provided through PCENTERS

Default: None - don’t use multiple phase centers

Usage: Keeps value of previous scan.

Example: CENTERS=P1305

COMMENT

COMMENT is a string of up to 128 characters to be written on operator and telescope files just before the scan.

Argument: Text up to 128 characters.

Options: Any.

Default: Blank

Usage: Reverts to no comment if not specified for each scan.

Example: COMMENT=’ET, call home.’

CORAVG

CORAVG specifies the correlator averaging time in seconds.

For the DiFX software correlator on the VLBA, there are two options for how the specified average time is treated. If all average times are to contain exactly the same amount of data and the time tags are to match exactly the mean time of the data, the interval must be an integer number of FFTs and of short-term accumulator intervals. The default behavior of the correlator is to adjust the average time to the nearest option that fulfills these criteria. That may well not be a very “round” looking number. The adjusted time will usually deviate from the requested time by only a few percent, although in some extremes of narrow bandwidth and many spectral channels, it can be as high as a factor of SQRT(2). An alternative behavior is offered where the correlator takes the exact value specified. It then bins the scan into intervals of that length and averages any short term integrations that fall in a bin. The data are given the time tag of the center of the bin. This allows the user to choose any desired integration time exactly. But the amount of data contributing to each integration will vary, typically by one short-term accumulation. Also the true mean time of a data point will be offset from the time tag by a variable fraction of a short-term accumulation period. To invoke this behavior, put the word EXACT as a second argument to CORAVG (not case sensitive).

For the original Socorro VLBA hardware correlator, valid values are an integer N times the speed up factor times 0.131072 seconds. Round values such as 2, 4, 8 seconds etc may be specified and the nearest possible value will be used. This is what is expected from most users.

The correlator default is 2 seconds but, at most frequencies, more is probably ok most of the time. The longer the on-line averaging, the smaller the output data rates and the smaller the output data set.

Note the correlation parameters CORAVG, CORCHAN, CORPOL, CORTAPE, and CORSHIPn must be specified when the project will be correlated in Socorro and data are being recorded.

Argument: A real or integer number followed by a string of up to 8 characters

Options: Any, but see above for useful numbers. The string can be anything but only ”EXACT” will mean to do something different from the default.

Default: Must be given for processing in Socorro. Otherwise 2.0. The string can, and usually will, be omitted.

Usage: Only one value used — the last.

Example: CORAVG = 4, exact

CORAVG2

CORAVG2 specifies the alternate correlator averaging time in seconds. Valid values have the same restrictions as CORAVG. This will be the average time used on baselines to spacecraft (eg HALCA) processed on the VLBA correlator. It will typically be smaller than CORAVG.

Argument: A real or integer number followed by a string of up to 8 characters

Options: Any, but see CORAVG for useful numbers. The string can be anything, but only ”EXACT” will mean to do something different from the default.

Default: 0.0 — not used. The string can, and usually will, be omitted.

Usage: Only one value used — the last.

Example: CORAVG2 = 1

CORCHAN

CORCHAN(1) specifies the number of spectral channels per baseband channel (one polarization component) that the correlator will write. CORCHAN(2) specifies the number of channels to use in the internal FFT in the correlator.

The VLBA correlator (both old and new) will, by default, make 128 channel spectra which are then channel averaged on-line for continuum observations. The typical number of output channels for continuum observations is the greater of 16 or twice the baseband channel bandwidth in MHz. Over averaging can cause loss of amplitude due to “delay smearing” — the effect of large phase slopes across the channels going into an average. Delay offsets can either come from a large field of view or from errors in the a priori clocks used in processing. The twice bandwidth number is determined by the clocks and should represent a minimum.

Corrections for this effect are made in AIPS, but the corrections are probably not perfect. Besides delay smearing, over averaging can lead to SNR loss when bandpass calibration is done. This is because edge channels are discarded as part of bandpass calibration because of the frequency shifts required to adjust for the effects of the fringe rotators (Doppler effect, essentially).

For spectral line observations, the DiFX correlator can do a vary large number of channels - ”it’s just software”. But excessive numbers of channels lead to excessive output data rates and data set sizes. Up to 4096 channels per baseband channel are supported normally and up to 32768 channels can be supported if needed and justified. There are no special restrictions in full polarization mode. The 32768 limit is set by the AIPS postprocessing path. Requesting too many channels can cause the data sets to be so large as to be difficult to impossible to manage. Also, the combination of the average time, the number of channels, and the number of baselines must be such that the output data rate is less than 10 Mbyte/sec. That is per second of observe time. The data rate in bytes/sec is given APPROXIMATELY as

4 * Ns * (Ns + 1) * Nc * Nsp * P / Tavg

where Ns = number of stations Nc = number of (BaseBand) channels (1, 2, ... 16) Nsp = spectral resolution (8, 16, 32 ... 512) P = 2 for polarization, 1 for none Tavg = time average in seconds

The second argument can be used to specify the size of the FFT used in correlators such as DiFX. Normally that argument can be ignored and the FFT size will be set to the larger of 128 or the first argument. The ability to set that argument is provided in support of the multiple phase center capability added to DiFX in 2010. When using that option, the spectral resolution of the transforms done before the different phase centers are split must be high enough that the differential delays, which show up in the data as a phase slope in frequency, do not cause smearing. See the discussion of multiple phase center processing for more details advice.

Note the correlation parameters CORAVG, CORCHAN, CORPOL, CORTAPE, and CORSHIPn must be specified when the project will be correlated in Socorro and data are being recorded.

Argument: Two integer numbers, usually a power of 2.

Options: Any, but see above for useful numbers.

Default: The first argument must be specified for the VLBA correlator. Otherwise it defaults to 16. The second argument defaults 128

Usage: Only one pair of values is used — the last.

Example: CORCHAN = 32 or CORCHAN=16,2048

CORDFMT

Data correlated at the VLBA is always archived. Most has been converted to FITS files for use with astronomical processing software. Some is now being converted to the types of files produced on the Mark4 correlators (Haystack etc). Those data can be processed through the geodetic oriented programs including Fourfit. To request production of a Mark4 file, specify ”CORDFMT = MARK4”.

Argument: A character string of up to 8 characters.

Options: Any, should be FITS or MARK4.

Default: Defaults to ’FITS’

Usage: Only one value is used — the last.

Example: CORDFMT=MARK4 or CORCHAN=16,2048

CORNANT

CORNANT informs correlator operations of the number of stations scheduled. This helps determine when all logs and media are in and helps determine what the correlator load, both in terms of drives needed and output data rate, will be. See the discussion of CORCHAN for a formula to calculate the output data rate.

The default value for CORNANT is the number of antennas scheduled which will nearly always be correct. There should be no need to specify a number other than in some special, very strange cases such as when more antennas are scheduled than will be correlated.

Argument: An integer number.

Options: Any, but it should be the expected number of antennas.

Default: Number of antennas in schedule.

Usage: Only one value used — the last.

Example: CORNANT = 10

CORNOTE1, CORNOTE2, CORNOTE3, and CORNOTE4

CORNOTE1, CORNOTE2, CORNOTE3, and CORNOTE4 provide four text strings with which to pass information to correlator operations staff.

This can be used to alert correlator operations to special requirements such as multiple phase centers, special positions, non-constant processing parameters etc.

Argument: Each parameter is a string of up to 128 characters

Options: An address

Default: Blank

Usage: Only one of each used — the last.

Example: CORNOTE1 = ’Please run the FD tape backwards.’

CORPOL

CORPOL can be either “on” or “off”. If it is “on”, all polarizations (RR, LL, RL, and LR) will be done. If “off”, only the parallel hand polarizations (RR and LL) will be correlated. Requesting full polarization (“on”) reduces the maximum number of spectral channels per baseband channel available and increases the output data rate. However for continuum projects with modest average times and 16 or 32 channels, neither of these is of much concern and there is little harm in asking for full polarization processing. Perhaps the data will even be useful eventually.

Note the correlation parameters CORAVG, CORCHAN, CORPOL, CORTAPE, and CORSHIPn must be specified when the project will be correlated in Socorro and data are being recorded.

Argument: Any 3 characters.

Options: “on” or “off” are the useful values.

Default: Required for VLBA correlator, otherwise “on”.

Usage: Only one value used — the last.

Example: CORPOL = ’on’

CORREL

CORREL specifies the correlator to which VLBI media and logs should be sent. This is for the cover information. SCHED will abort if this parameter is not given unless this is a VLA only observation or a single dish observation (eg VLBA pointing). Allowed values are Socorro, VLBA, Haystack, Bonn, JIVE, Washington, USNO, Jpl, Bologna, Mitaka, Penticton, ASC, and Other (which should be followed by the name). The name is not case sensitive.

The first word of CORREL must be one of:

Socorro, VLBA, or VLBADIFX (VLBA DiFX software correlator)

Haystack,

Bonn (MPIfR DiFX correlator),

JIVE,

Washington or USNO,

LBA,

JPL,

Bologna,

Mitaka,

ASC (Astro Space Center - Moscow)

Penticton, or

Other

FXCORR (Original VLBA hardware correlator — no longer exists so SCHED will stop.)

Note the correlation parameters CORAVG, CORCHAN, CORPOL, CORTAPE, and CORSHIPn must be specified when the project will be correlated in Socorro and data are being recorded.

Argument: Text up to 62 characters.

Options: See list above for valid options.

Default: Blank which causes SCHED to abort.

Usage: Only one value used, the last.

Example: CORREL=VLBADIFX

CORSRCS

CORSRCS is a character string instructing the correlator staff where to get the source coordinates. STANDARD will imply to get them from the correlator catalog. This is an extensive list of sources based on USNO geodetic/astrometric solutions or, for sources for which VLBI positions are not known, from the VLA calibrator list. SCHEDULE will mean to get the positions from those used in this schedule. Other statements can be made - this information will be read by the correlator operations staff. If more room is needed, see the CORNOTE parameters.

Argument: Text of up to 64 characters.

Options: STANDARD and SCHEDULE are useful. Others can be used.

Default: STANDARD

Usage: Only one used — the last.

Example: CORSRCS = ’PI will provide before correlation.’

CORSHIP1, CORSHIP2, CORSHIP3, and CORSHIP4

CORSHIP1, CORSHIP2, CORSHIP3, and CORSHIP4 provide four character strings in which to specify the place to ship the correlator distribution .

Note the correlation parameters CORREL, CORAVG, CORCHAN, CORPOL, and CORSHIPn (if CORTAPE = DAT or EXABYTE) must be specified when the project will be correlated in Socorro and data are being recorded.

Argument: Each parameter is a string of up to 64 characters

Options: An address

Default: Blank — Which causes and abort if you requested shipable media.

Usage: Only one of each used — the last.

Example: CORSHIP1 = ’Phil Diamond’

CORSHIP2 = ’NRAO’

CORSHIP3 = ’P.O. Box O’

CORSHIP4 = ’Socorro, NM, 87801’

CORTAPE

CORTAPE specifies the type of media that should be used for the data distribution from the correlator. This must be FTP, DAT, DISK or NONE. FTP and NONE basically mean that the PI will pick up a disk copy of the data by means of a network copy (there is no effective difference between the two). EXABYTE was recently removed for lack of use, as 9TRACK was long ago. DAT will likely go soon. FLASH may get added some day, but not yet.

Argument: A string of up to 16 characters

Options: DAT, DISK, NONE, or FTP

Default: Blank, which causes and abort if data are being recorded.

Usage: Only one used — the last.

Example: CORTAPE = ’DISK’

CORWTFN

CORWTFN specifies the weighting function to be used on the VLBA correlator. The weighting function is applied by weighting the data points before they are sent to the FFT. Valid options are:

UNIFORM. No weights are applied. The data are used as is. The is the option that most users will want.

ZEROPAD. With this option, the input data for the FFTs are padded with zeros by a factor of two. This reduces the resolution of each spectral point. With the FX correlator, the frequency response of each spectral channel is sharper than with an XF correlator and this may not be what is desired for some spectral line observations. If so, ZEROPAD is a way to reduce the effect. Actually reproducing the frequency response of an XF correlator is possible in theory, but not with any of the available windowing functions. Note that ZEROPAD should not be used with the 1:4 fan out because that causes there to be no overlapping of FFTs so half the data are not used.

HANNING. With this option, a Hanning weighting is applied in before the FFT. This is done in the voltage (sample) domain and has the effect, after cross correlation, of applying a “Hanning squared” weighting on the final power spectra. This is probably not what the user wants.

QANNING. With this option, an approximation of a “root Hanning” weighting is applied to get close to the expected Hanning response in the power domain after correlation. It is only an approximation because the windowing function cannot have the negative values that would be required to do this exactly.

Eventually more options may be available.

Argument: Any text string of up to 16 characters

Options: UNIFORM and HANNING are the useful options.

Default: UNIFORM

Usage: Only one value used — the last.

Example: CORWTFN = ’HANNING’

COVERLET

COVERLET alerts the program that all lines after the next ’/’ and up the the occurrence of ’endcover’ and ’/’ on a line will be text that is to be transferred to the summary and operator schedule files (sch. files). This allows the PI to write a cover letter that will make it into files that the operators at at least some stations will see, hopefully eliminating the need to write a separate cover letter file. The amount of text is arbitrary and the line need only be shorter than 256 characters. Lines over about 80 characters may not look good in the output.

Note that the operators at some telescopes, including the VLBA, do not pay much attention to what is in the files. Cover letters of any type are not very effective. Your observation should be described well by the parameters that actually control telescope operations. Cover letters can be effective for observatories where some operations have to be done by hand.

The egglobal.key example shows the use of COVERLET.

Argument: none

Options: No argument required or useful.

Default: It will be assumed that there is no cover letter.

Usage: Only use preceding the cover letter input.

Example: COVERLET /

CRDBW

CRDBW is used in the main schedule when using either CRDFREQ or CRDDOP to set frequencies on the VLBA for the legacy system that are different from what is set for the RDBE. This is mainly to allow Doppler setting for masers for reference pointing, which is recommended at 86 GHz. See CRDFREQ for more details.

The channels should correspond to the channels in the current setup file because configuration information like the IF, first LO, sideband, etc will be taken from the setup. Only 8 channels will actually get used as, when the RDBE is in use, for bookkeeping ease, only one channel will be assigned to each bbc.

This parameter is equivalent to BW, but is only for use when using the RDBE but wanting different settings in the old system. It will be ignored except on the VLBA using the RDBE.

Any unset values will be set to the same as the first channel. It is good practice to set to 0.D0 when not in use, which may require setting all channels explicitly.

Argument: A list of bandwidths in MHz, one per channel.

Options: 0.0625, 0.125, 0.250, 0.5, 1, 2, 4, 8, or 16 MHz

Default: It is required if CRDFREQ or CRDDOP is used.

Usage: Retains the value from the previous scan if not set.

Example: CRDBW= 2.0, 2.0, 2.0, 2.0 /

CRDDOP and CRDNODOP

CRDDOP requests Doppler frequency setting for the VLBA legacy system BBCs. It is much like DOPPLER except that it should only affect the BBCs, not the RDBE. This is needed because the legacy system still controls the antenna pointing and does not have access to power levels from the RDBEs, which are controlled by the separate new control system. The total power data from the legacy BBCs are used to make the pointing measurements. See the discussion of CRDFREQ for more details about using the CRDxx parameters.

When using CRDDOP, you must also set CRDBW and one (and only one) of CRDCH1 or CRDSETCH.

As an alternative to requesting SCHED do Doppler calculations, you can force a specific frequency with CRDFREQ.

Specify CRDNODOP to turn off the BBC Doppler setting.

It is not recommended to attempt to use DOPPLER and CRDDOP at the same time, although it might work.

Argument: No argument

Options: None

Default: Do not use CRDDOP

Usage: Uses previous scan value if not specified

Example: CRDDOP

CRDLINE

CRDLINE allows the scheduler to insert an arbitrary string into the crd control files for VLBA antennas. It is intended to simplify the testing of new features by someone programming the on-line system. You almost certainly don’t want to use this parameter unless you are a VLBA programmer.

Argument: A character string of up to 80 characters.

Options: Any character string.

Default: Blank

Usage: One per scan. Remains at most recent value set.

Example: CRDLINE = ’This was requested by Walter’

CRDCH1

When setting parameters for the VLBA legacy hardware different from what is being set for the RDBE, parameters CRDFREQ, CRDDOP, CRDNCH, CRDBW, CRDSETCH, and CRDCH1 can be used. Many of the channel parameters are taken from the main setup. These include sideband, sample rate, IF channel etc. With the legacy system “CRD” parameters, only 4 channels (8 before early 2014) can be specified. With the RDBE_PFB, the number of setup channels is 16 while it can be up to 8 with the RDBE_DDC. By default, SCHED will try to spread the crd channels broadly over the setup channels and, in particular, will try to have at least one crd channel from each IF. CRDCH1 gives the opportunity to specify the first channel of a contiguous block of CRDNCH channels to use. Alternatively, one can use CRDSETCH to specify the template channels individually — probably the preferred option if not taking the default.

Argument: An integer

Options: Any integer 16 or less

Default: SCHED has an algorithm for distributing the channels broadly, making sure all IFs are represented.

Usage: One per scan. Defaults to last value.

Example: CHDCH1 = 5

CRDNCH

CRDNCH sets the number of channels to use on the legacy VLBA hardware (BBCs especially) when using the RDBE. The main reason for being concerned about the legacy hardware is that the power levels in the BBCs are used by the old control system to do reference pointing. See also CRDFREQ, CRDDOP, CRDBW, CRDCH1 for controls related to such reference pointing, especially with masers.

CRDNCH is a required parameter when CRDFREQ or CRDDOP are set.

When not using CRDFREQ or CRDDOP, CRDNCH will still set the number of channels used in the crd files controlling the BBCs. If CRDFREQ and CRDDOP are never used, CRDNCH will be set to lesser of 4 (the number of BBCs after April 2014) and the number of setup channels.

When CRDNCH is less than the number of channels in the main setup (typical if using the RDBE_PFB), then the alignment between the main setup channels and the legacy system channels can be set using CRDCH1

Argument: An integer

Options: Any integer 4 or less

Default: The lesser of NCHAN for the setup and 4 (number of BBCs after April 2014.)

Usage: One per scan. Defaults to last value.

Example: CHDNCH = 2

CRDFREQ

This parameter is equivalent to FREQ, but is only for use when using the RDBE but wanting different settings in the old system. It will be ignored except on the VLBA using the RDBE. The main use will be for 86 GHz observations using the PFB personality of the RDBE. With the PFB, the bandwidth per channel can only be 32 MHz and the frequencies are not flexible. To reference point on masers, it is necessary to use the legacy BBCs with narrower bandwidths and with frequencies that are not closely related to the main setup frequencies. Such settings can be determined from Doppler calculations using CRDDOP or set explicitly using CRDFREQ. Note that CRDBW must also be set if either of these options is used.

When CRDFREQ or CRDDOP is used, the resulting frequencies appear in the xxcrd.ss files that control the VLBA legacy system. They do not appear in the VEX file. As of this writing, they also don’t appear on the summary file, although changes can trigger specification of a new setup group that may not obviously be different from another group, if the only change is in the setup parameters.

Any unset values of CRDFREQ will be set to the same as the first channel’ value. It is good practice to set to 0.D0 when not in use, which may require setting all channels explicitly.

It is expected that this capability will be retired when the new control system takes over antenna pointing. At that time, any projects requiring reference pointing on masers will need to use the DDC personality of the RDBE, which allows fine tuning and narrow bandwidths.

Argument: A list of RF frequencies in MHz, one per channel.

Options: Any allowed RF frequency MHz

Default: Use values based on the setup file, with adjustments based on the limitations of the BBCs relative to the RDBE

Usage: Retains the value from the previous scan if not set.

Example: CRDFREQ= 43122.03, 43122.03 /

CRDSETCH

CRDSETCH is a list of setup file baseband channels to use for many channel dependent parameters such as IF channel, polarization, etc when setting up the channels for the VLBA legacy system. There can be as many entries as there are legacy system channels. As of early 2014 when 4 BBCs are being removed, that number is only 4. The effect is only on the crd files, not the Vex file.

This parameter can be very important when using the S/X system on the VLBA. The new VLBA control system will know that both S and X band receivers are in use and will set the hardware accordingly. Critically, it will or will not deploy the ellipsoidal reflector over the X band receiver. If the channels sent to the legacy control computer (the crd files) do not contain any S band channels, then that system will think this is an X band only observation. It has control of the subreflector so it will point the subreflector at the X band receiver. But that optical path is now blocked by the ellipsoid. So no source data will get through. However all other parameters like system temperature and pulse cal will look ok. You end up with hard-to-diagnose lack of fringes. This situation can, and has (guess how we know about this!) happened when there are many X band channels and only a few S band channels as is likely when using the RDBE_PFB.

Argument: A list of setup file channel numbers - up to 4. This can be changed on a scan basis

Options: Any channels

Default: If not used, and CRDNCH is not used, SCHED will make a reasonable selection, including making sure all IF channels are represented.

Usage: Defaults to previous scan

Example: CRDSETCH = 3,4,7,8

DATAPATH

This is an eVLBI control parameter. Be warned: eVLBI support is under development. The eVLBI parameters are GRABTO, GRABTIME, GRABGAP, and DATAPATH.

DATAPATH determines where the main data flow goes. It is meant to be used with systems like Mark5 that have an eVLBI (over the net) capability. The data can either go to disk as in normal observing DATAPATH=IN2DISK or it can go directly to the network DATAPATH=IN2NET.

When the data are sent to disk, there is an option to send small amounts over the network later for fringe checks and the like. That option is controlled by the GRAB... parameters.

Argument: Character string of up to 8 characters.

Options: IN2DISK for normal recording to disk or tape - the default. ’IN2NET’ for real time eVLBI with correlation or recording at a remote location.

Default: IN2DISK

Usage: A value for each scan. Defaults to previous scan.

Example: DATAPATH = ’IN2NET’

DAY

DAY is the day number of stop time of scan. Day 1 is the first day of the month specified with the MONTH parameter, which defaults to 1 so that DAY is the day of year. If LST was specified, DAY must be the (modified?) local sidereal day number for the reference station. These numbers are printed on the right side of VLA monthly schedules and are near 56800 in 1996.

Argument: Integer.

Options: Any.

Default: Required for first scan - no default.

Usage: Defaults to previous scan. Only need for first scan if using durations even if project crosses day boundary.

Example: DAY=135

DEBUG

DEBUG is a switch that turns on some debug printouts. It is unlikely to be useful to users, only to programmers.

DODOWN

Normally, SCHED eliminates stations for which the source is not up if they are using a disk recording system. DODOWN with no argument overrides that behavior and keeps stations in scans regardless. DODOWN can be set differently for each scan. Setting it to any non-zero value sets it to false (ie - go ahead and remove stations).

In the tape era, only VLBA stations were eliminated and only if AUTOTAPE was set to 2.

Without DODOWN, SCHED will also take a station out of a scan if the predicted slew time is such that the antenna will not reach the source before the scan end. However, it was found that this can prevent wraps from occurring in a timely manner during fast switching operations such as phase referencing, when one source needs the wrap a while before the other. Therefore, SCHED will not remove a station from a scan if mount type is ALTAZ and the requested azimuth slew is greater then 315 degrees. Such long azimuth slews would normally mean that a wrap is needed so getting it started is useful. There is no perfect algorithm to always do the right thing here so some though may be required by the PI if the behavior is odd. DODOWN is now scan dependent to help with dealing with odd behavior. Also explicitly including or excluding stations from the scan can be a strong tool for dealing with problems. Beware of special instructions when there is a chance that a program will be time shifted for dynamic scheduling. That will change when things like wraps need to happen.

Note that SCHED does not presume to tell the antenna what wrap to be on, mainly because there is no mechanism to do so with the VLBA. Some day this may change in which case SCHED can be more intelligent about what to do. For now all SCHED can do is control what scans are present and guess what the antenna will do.

Argument: None

Options: No argument

Default: Stations taken out of scans (DODOWN not zero)

Usage: One per scan. Defaults to previous value.

Example: DODOWN or DODOWN=-1

DOMKA

DOMKA (read DO-MKA) is a switch to request that, when observing with the RDBE and MARK5C, that a parallel MARK5A recording be made. It is expected to be used mainly for testing.

Argument: None

Options: No argument

Default: No Mark5A)

Usage: Only last used.

Example: DOMKA

DOPCAL

DOPCAL is an obsolete form of the parameter DOPPLER. It is no longer recommended because of possible confusion with DO PCAL.

DOPINCR

DOPINCR sets the frequency increments to use in setting frequencies using DOPPLER. The frequencies will be rounded to the nearest N * DOPINCR(1) + DOPINCR(2). The default for DOPINCR(1) when the RDBE is not in use is 10 kHz, the setting interval for the BBCs for the DBBC, LBA, and the legacy VLBA and Mark III/IV systems. For the RDBE_DDC option for DBE, the default is 15.625 kHz. For mixed legacy/DBBC/MARKIV and RDBE observations systems, the default is 250 kHz, the smallest value that is a multiple of both 10 kHz and 15.625 kHz. It is best not to use DOPPLER with the RDBE_PFB personality because of the tight tuning restrictions and the fact that the offset DOPINCR(2) depends on the LO setup. The ATCA LO is set in intervals of 1 MHz + 0.5 MHz.

The values are in kHz. A new value may be given for each scan, although usually a single value would be used for the whole experiment.

Argument: A number specifying a frequency in kHz.

Options: Any number.

Default: Depends on DBE — see text.

Usage: A value for each scan. Defaults to previous scan.

Example: DOPINCR = 1000,500 (appropriate for ATNF 20 GHz)

DOPPLER and NODOP

DOPPLER and NODOP control Doppler calculations for this scan. DOPPLER turns them on, NODOP turns them off. See Section 2.5 for details.

Note that channels assigned to the same BBC will be given the same frequency as the first channel on that BBC, no matter what velocities etc are given for the other channels. This will be the case when there are upper/lower sideband pairs. Their frequencies cannot be set independently. Because of the different sidebands, they will, however, cover different velocity ranges.

WARNING — if you are making extragalactic observations with high velocities (above about 1000 km/s), be sure to pay attention to the parameters VREF and VDEF in the source catalog. Extragalactic velocities are likely to be based on the “optical definition” which is not the SCHED default. Also, they are likely to be heliocentric, which is also not the SCHED default. In such a case, you would want to specify VDEF=O VREF=H. Note that you are also allowed to give z directly with VDEF=Z.

Argument: None.

Options: 0 or nothing to get Doppler calculations. A non-zero value will turn them off, but use of NODOP is a more convenient way to do the same thing.

Default: Don’t do Doppler calculations.

Usage: Reverts to previous scan.

Example: DOPPLER

DOSCANS

The user can specify optional scans on the ends of a project using the PREEMPT parameter. Those scans will be shown in the summary file .sum file, but will not be sent to the telescope control and others files (.vex, crd.xx, sch.xx, .oms and .flag files. To actually utilize those scans, or for that matter, any arbitrary subset of all the input scans, specify the range of desired output scans with DOSCANS. The arguments are the scan numbers of the first and last scans as they appear in the summary file.

It is intended that DOSCANS be used mainly by the VLBA scheduler while trying to put together dynamic schedules. It is often hard to find projects that mesh together exactly without leaving gaps. The PREEMPT=EXTRA and DOSCANS parameters are intended to let users provide productive observations to make during such otherwise unfilled gaps.

Note that DOSCANS can be used in conjunction with parameter WRAP24 to rotate the start point of full day schedules around the clock for more convenient dynamic scheduling.

Argument: Two integers

Options: Values that correspond to scan numbers in the .sum file

Default: zero - don’t use this scan restriction

Usage: One set of values used for the whole project

Example: DOSCANS = 154, 367

DOPSRC

DOPSRC is the name of the source for which the Doppler calculation should be done. This is allowed to be different from the source being observed to allow for observing continuum calibrators at the same frequency as the line source. If it is blank, the source being observed will be used. If it is not specified, the previous value will be used so it must be set to blank after use in earlier scans if it is desired to return to the original default.

A warning will be issued if SOURCE and DOPSRC are different and both have velocities specified (assumed to be line sources). This is a valid but unlikely observing style so it is not blocked. But too often it has been the result of ignoring the warning above about the defaulting behavior of DOPSRC.

Argument: A source name.

Options: Any source in the source catalogs.

Default: Blank - use SOURCE.

Usage: Reverts to previous scan. Can set to to return to default behavior.

Example: DOPSRC=’W3OH’

DOSTA

DOSTA tells SCHED to process only those stations whose names match the value given for DOSTA to as many characters as given for DOSTA. This is intended primarily for telescope friends who wish to rerun SCHED using the keyin file provided by the observer and who do not want output for all stations. Requiring a match only on the specified characters allows DOSTA=’VL’ to be specified to obtain all VLBA and VLA files. DOSTA affects the stations read for the current scan. Normally it would be specified among the first set of inputs and not changed. In this case, it will affect the whole schedule.

Argument: Text of up to 8 characters.

Options: Any station name or portion thereof.

Default: None

Usage: Defaults to previous scan.

Example: DOSTA=’VLBA’ makes all VLBA files.

DOVEX

DOVEX tells SCHED to write a VEX format output file. It is now the default so the parameter can be used to turn off writing of the VEX file. VEX is the format originally used by PCFS, the NASA/Goddard field system that controls EVN, geodetic and other stations. It is now used to control most correlators including the VLBA and other DifX correlators, the JIVE correlator and the geodetic correlators based on the Haystack design. VEX files will also eventually be used for control of the VLBA stations and the EVLA for VLBI. So a VEX file is required for essentially all VLBI observations now.

Argument: None.

Options: No argument required. If one given, DOVEX will be false.

Default: DOVEX will be true unless given a non-zero argument.

Usage: Only one value used — the last.

Example: DOVEX=-1 --- to turn VEX outputoff

DURation

The topic of controlling scan timing is discussed in detail in the Scan Times section.

DURation specifies the length of the current scan. Usually this is used instead of STOP. It is assumed to be a UT time interval unless LST was specified, in which case it was assumed to be an LST time interval. DWELL is a very similar parameter except that, with DURation, the scan starts GAP seconds (perhaps adjusted by the old parameter PRESCAN after the previous stop time while with DWELL, the scan will start at least GAP seconds after the previous stop time, but, if necessary, will wait longer to allow all antennas to reach the source.

Note that DUR and DWELL may be both be used in the same schedule, but cannot both be used for the same scan (that would not make sense). If either is used, the time specified overrides any previous specification of the scan length made with either parameter.

Once the nominal scan start time has been specified as above it can be adjusted further with the old, and mostly obsolete, parameter PRESCAN. Then the actual time that recording starts is adjusted further with MINPAUSE and PRESTART. PRESTART, MINPAUSE, and PRESCAN allow the user to start recording early to give the correlator a chance to synchronize before the start of good data. PRESTART can also be used to delay the scan start to be more sure it starts on good data — mostly useful with DWELL. These parameters also can help prevent short stoppages which used to cause problems with playback with tape systems. Adjusting the media start time should no longer be needed for correlators and recording systems currently in use (eg MARK5 and DiFX). See the descriptions of the parameters mentioned for more information. The SCHED defaults are generally reasonable so, if you are not an experienced user who wants to exercise fine control of recording management, don’t worry about these parameters.

The start and stop times reported in the summary and operator schedule files are the same for all stations. They take into account any adjustments made as a result of specifying PRESCAN, but do not take into account adjustments requested using MINPAUSE and PRESTART, since those can be station dependent. The time the media is started is reported in the sch.xx files under the heading ”TPStart”.

With the VLBA RDBE recording system and DiFX correlators, both recording and correlation start times ignore most of the efforts by SCHED to adjust recorder start times. They treat the data-good time as given as an offset from the start time in the $SCHED section of the VEX file as the time to start handling data. In the $SCHED section, there can be two start times, one commented out (line starts with “*”). The commented one is the nominal start time as seen in the SCHED summary file. The active one is what SCHED thinks is the media start time, usually the nominal start time minus PRESTART. Then on each station line, there are two offset times, one for the start and one for the stop. The start is greater of zero and the time when SCHED thinks the data will be good (on-source etc). That is what is used by the VLBA to start recording and DiFX to start correlation. So effectively, even when using duration scheduling, you are fairly likely to actually be using dwell scheduling.

See the Scan Times section for more information on the specification of scans.

Argument: A time in format hh:mm:ss, mm:ss, or ss.

Options: Any.

Default: Not used.

Usage: Defaults to previous scan. Overridden by DWELL.

Example: DUR=13:00

DWELL

The topic of controlling scan timing is discussed in detail in the Scan Times section.

DWELL is an alternate way to specify the duration of a scan. It is distinguished from DURation only in that the start time of the scan will be delayed until SCHED expects all antennas to be on source. Both the slew time, including acceleration, and the settling time from TSETTLE in the station catalog will be taken into account. The interval between scans will not be allowed to drop below MINSETUP from the antenna catalog to allow for finite scan setup times at some antennas. SCHED tries to arrange that useful data will be obtained for the full time specified by DWELL. With DURation, some of the specified time may not have good data because antennas are still slewing. Please see the description of DURation for a more complete discussion of the actions of these two parameters and their interactions with other parameters that influence scan times and recording activity.

As of Oct. 2010, DWELL has acquired second and third arguments. Argument 2 is the number of antennas to not wait for. Typically it will be a small integer like 1 or 2, but can be up to the number of antennas (not sure what that would do!). This should be useful if the there is a problem with long slews between pairs of sources near the zenith at one antenna. It would also be useful if you wish to let the less sensitive, but faster, antennas start observing once they are on source on the assumption that large, slow antennas might not need as much integration time. This is an issue with global observations or HSA. SUMITEM = EARLY can be used to inspect the results of the use of the second DWELL argument. For example, with that argument set to one, one antenna should have EARLY negative (got there after the start).

The third argument is a minimum time on source for the antennas that are not being waited for thanks to argument 2. The default zero for this argument allows the scan to end before the slow antenna(s) get to source. If a time is specified, then the scan will be extended until the last antenna gets that much time. In such a circumstances, the scan will still start when first group of antennas (other than those the second argument says not to wait for) get to source, so those antennas will get a longer scan than specified.

Please note that the model SCHED uses to calculate slew times is not especially sophisticated, especially in regard to the excess times beyond the slew that an antenna might take to start getting good data. It is adequate for most purposes, but, for example, it might not agree exactly with other programs such as the VLA scheduling program Observe. In such cases, the station specific program probably has the better answer. Also, for some systems, such as the VLA, SCHED is more interested in when VLBI data starts to be good which might be before a local correlator starts to get good data. As of Feb 2003, SCHED does take into account the time an antenna takes to accelerate to full slew speed, and should calculate slew times for short slews approximately correctly even if full speed is not reached.

Argument: A time in any allowed time format (hh:mm:ss, mm:ss, sss etc.), followed by an integer, and then another time.

Options: Any time. The integer should be smaller than the number of antennas. The second time is normally smaller than the first

Default: The duration of the scan must be specified with some combination of START, STOP, DURation, and DWELL. The number of antennas to not wait for defaults to zero as does the minimum time.

Usage: Reverts to previous scan. Overridden by DUR. The second and third arguments use the last setting in a DWELL command (not overridden by DUR)

Example: DWELL=110,1,60 (which is equivalent to DWELL=1:50,1,1:00). DWELL=110 is equivalent to DWELL=110,0 except that the latter will reset the second argument to zero if it had been something else while the former will not.

ELCOLIM

ELCOLIM can be used to specify an increment to the elevation collimation offset value used for pointing. This is added to the nominal position known by the on-line system for the particular receiver and to the value specified in the setup file. It is also added to the values used for offsets in pointing patterns and to any value from the setup file.

Argument: A elevation collimation offset in arc minutes.

Options: Any value.

Default: 0.0

Usage: Default to previous scan.

Example: ELCOLIM = 0.25

EMAIL

EMAIL gives the principal Investigator’s electronic mail address for the cover information. Use an Internet address where possible. Either of EMAIL or FAX must be provided if recording VLBI data. Both should be provided.

Argument: Text of up to 64 characters.

Options: Any.

Default: Blank

Usage: Only one value used, the last.

Example: EMAIL=cwalker@nrao.edu

EPHFILE

EPHFILE is used to specify the location of the JPL ephemeris file. This is only needed if SCHED is being asked to calculate the position of one or more objects using the ephemeris. This is done by including a recognized planet (or other body) name among the sources and not providing a source catalog entry for it (if there is a catalog entry, that is used instead).

The objects that SCHED understands are Mercury, Venus, Moon, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, and Sun. Topocentric positions and rates will be provided for VLBA antennas if one of these is specified. Geocentric positions along with rates and horizontal parallax are provided for the PM cards for the VLA. Note that SCHED does not understand how to specify moving objects to antennas that don’t use the VLA or VLBA control file types.

Under unix, environment variables may be used. For example, if SCHED is defined to mean /users/cwalker/sched, the base area under which all sched stuff is kept (substitute your local directory), then one can specify the ephemeris file with EPHFILE = $SCHED/catalogs/newfile.eph, if that were where it is (it isn’t!). Use the setenv (c or t shell) or export (korn shell) to set environment variables.

At the AOC, for now, the ephemeris file is on Brian Butler’s computer in the location shown in the example below. There is also a copy in the SCHED catalogs subdirectory.

Note that if planetary observations specified to stations that use the VEX file, the positions passed will not be of adequate quality for correlation and maybe not for pointing.

Argument: Text of up to 80 characters - a file name.

Options: Any valid file

Default: ’NONE’

Usage: Only one value used, the last.

Example: EPHFILE=/planets/ephemeris/JPLEPH.403.2

EXIT

EXIT terminates interactive input. It has the same effect as reaching the end of file when input to SCHED is from a keyin file. It should be issued after the “/” after the last scan and needs a “/” of its own. Any inputs issued with it will be ignored. Since SCHED is nearly always used with an input file, this parameter should rarely be used.

Argument: None which implies 0.D0.

Options: None.

Default: Not issued if non-zero.

Usage: Will terminate program so only can be used once.

Example: EXIT /

EXPT

EXPT is a description of the project for the listings.

Argument: Text up to 72 characters.

Options: Any.

Default: None.

Usage: Only one value used, the last.

Example: EXPT=’3C345 March 11, 1988 Mark II’

EXPCODE

EXPCODE is the project code from the Network or from NRAO. This is used as the first few characters of many file names.

Argument: Text of up to 8 characters. Best to use 6 or less. In fact, only 5 characters will be kept by much of the NRAO bookkeeping system.

Options: Any.

Default: ’NUG’

Usage: Only one value used, the last given.

Example: EXPCODE=BW005

FASTFOR

FASTFOR: is an obsolete parameter that only applies to tape.

FASTFOR: requests that the wide band tape (Mark III or VLBA) be run at the maximum forward speed during the prescan. Usually the intent is to get to the end of the tape prior to the start of the scan. If no argument is given, all stations will be issued with a fast forward instruction. If a list of stations is given, only those stations in the list will be fast forwarded. The station code may be used instead of the station name (not case sensitive).

Argument: None or a list of stations.

Options: None or a list of any stations in the scan. Not case sensitive.

Default: No fast forward unless there is insufficient room on the tape to complete the scan while recording in the current direction.

Usage: Reverts to no fast forward on next scan.

Example: FASTFOR or FASTFOR=VLBA_BR

FAX

FAX is the Principal Investigator’s FAX number for the cover information. Either an EMAIL address or FAX number must be provided when recording tape. Both should be provided.

Argument: Text of up to 64 characters.

Options: Any.

Default: Blank

Usage: Only one value used, the last.

Example: FAX=’+1-505-835-7027’

FOCOFF

FOCOFF gives the offsets in focus for a focus/rotation raster. See ROTPAT for details.

The values are offsets to be multiplied by the nominal offset for the band as understood by the program.

Argument: Up to 20 real numbers - the number of nominal recrements in focus for each position of a focus/rotation raster.

Options: Any number. 1.0 or 1.5 typically.

Default: 0.0

Usage: Only one set used per experiment.

Example: FOCOFF=0,-1,0,1,0

FOCUS

FOCUS is used in VLBA test observations to specify an increment to the focus value used for the subreflector position. This is added to the nominal position known by the on-line system for the particular receiver.

Note that the schedule requires focus values in mm while tsm reports focus achieved in cm.

This parameter might be used in astronomical observations if one wished to have the most optimum focus for a given frequency for a receiver that has a significant focus variation with frequency. The new (2012) 6cm receiver (4-8 GHz) has such a variation.

Argument: An incremental focus position in mm.

Options: Any incremental focus position.

Default: 0.0

Usage: Default to previous scan.

Example: FOCUS = 10.2

FREQ

FREQ specifies the LO sum observing frequencies for the baseband channels in MHz. When not specified, the last value specified is used. If 0 is specified, or FREQ is never given in the schedule, the default from the setup file is used. Any channels not specified will be set to the same frequency as the first. This defaulting only works when that channel was not previously set to an explicit value. The defaulting to the first channel is usually not what is desired. Whenever the frequencies change, a comment appears in the operator schedule file; the appropriate changes are made to the BBC frequencies for antennas using VLBA or VEX control files; and for snap files, dummy video converter commands are written without the correct video converter number and with the full LO sum (personnel at “snap” sites must edit in the correct video converter numbers and subtract the first LO). Since both the VLBA and Mark IV systems can only set frequencies to the nearest 10 kHz and the Mark III video converters are often used for Mark II projects, do not try to set a frequency that is not an even 10 kHz. Actually, SCHED will round to this value, or to DOPINCR, if it is given.

Argument: Up to 16 real numbers in MHz.

Options: Any.

Default: Use the setup file values.

Usage: Uses the last value specified.

Example: FREQ=22236.78,22238.78

FREQFILE

FREQFILE is used to specify the file containing the standard frequency setup information. This file is provided with SCHED and most users only need to point to it. If you want a setup that does not match one of the standards, SCHED will allow you to use one although it will issue warnings to remind you to be sure you know what you are doing.

On unix, an environment variable may be used.

For additions or corrections on EVN telescopes, contact Des Small at small@jive.nl.

A file name of up to 80 characters. Any. $SCHED/catalogs/freq_RDBE.dat Uses the last value specified. FREQFILE=/users/cwalker/sched/catalogs/freq.dat

FREQLIST

FREQLIST is used to request a table of information from the FREQFILE be written to frequencies.list. It takes two arguments giving a frequency range to be covered in the list (in MHz). If the second argument is omitted, it will be set equal to the first. This may be the only parameter given to SCHED — no others are needed. SCHED will quit after the table is made. This facility should be useful for determining which antennas can observe certain frequencies.

2 real numbers which are frequencies in MHz Any. Not used. No table written. Uses the last value specified. FREQLIST=4900,8600

GAP

The topic of controlling scan timing is discussed in detail in the Scan Times section.

GAP is the minimum gap in time between the previous stop time and the current nominal scan start time when scheduling with DURation or DWELL. For scheduling with DURation, it will be that time interval. For scheduling with DWELL, the interval might be longer if required for slews, but it will not be shorter. Note that PRESTART, PRESCAN (old, mostly obsolete parameter) and MINPAUSE are applied after the nominal scan times are established and could make the period during which the recording is stopped shorter than GAP. MINPAUSE is used to keep the recordings going through short gaps. Note that, if START is specified, GAP will be ignored.

If LST scheduling, GAP is a sidereal time, so it will be slightly shorter in UT (by about 1.0027).

For all types of scheduling, if the gap between scans is less than the value of MINPAUSE, the recordings are left running. The default MINPAUSE is 10 seconds for legacy systems and the DBBC. It is zero for the RDBE and WIDAR.

For Field System stations (most non-VLBA stations), gaps should be inserted to allow bank changes. The VLBA can switch between mounted disk banks (modules) on the fly, but the field systems need a pause in the data recording. Such gaps should be inserted every 22 minutes for recordings at 1 Gbps and proportionally less often at lower bit rates. These gaps need to be more than 10s long.

The PCFS software requires an interval of 36 seconds at tape reversals (not needed for disk) to produce a valid VEX file. A 40 second gap is required to change setup. Apart from these restrictions continuous recording is implied for gaps shorter than 10 seconds. In addition, users should realize that during continuous recording no calibration data is taken. Starting and stopping the recording can be forced using GAP or PRESCAN, or by using START times. GAP is probably the preferred mechanism. As of Feb. 2014, we are trying to determine what is the current minimum time for bank changes. It is actually likely to be less than 40 seconds.

There is an interaction between GAP and AUTOPEAK. Any specified GAP will be enforced for the interval between the input scans, but the inserted pointing scan can occur during that interval. Note, prior to Feb 2014, the gap was set to zero when pointing was inserted, so under some circumstances, the input scans could end up closer together than GAP.

Argument: A time in any approved time format (hh:mm:ss, mm:ss, sss etc.)

Options: Any time

Default: Zero.

Usage: Reverts to previous scan.

Example: GAP=2:00 (which is equivalent to gap 120).

GEOBACK

GEOBACK is a knob sticking out of the algorithm that selects sources for use in a geodetic segment. For the current source selection algorithm, it is not too useful and should be set to a value higher than the number of scans expected in the segment. The default is 100. For each new source, SCHED looks for which sources of those available would contribute the most to improving the rms of the SecZ parameters in a dummy fit. That dummy fit does not use all the sources in the segment so far, but rather is restricted to the last GEOBACK sources. Without that restriction, once all antennas are giving reasonable SecZ fits, no new source improves things much and the bias to short slews can lead to selection of sources that don’t really contribute much to the segment. By restricting the look-back, each new source must contribute to a fit. Since the algorithm was changed to concentrate on the antenna that did worst in after the previous source was added, rather than the RMS improvement, this restricted look-back capability has not been especially useful.

GEOBACK is also used to inhibit repeated use of any given source in a segment. Rather than prohibit repeats entirely, SCHED only prohibits repeats within each GEOBACK scans.

Argument: A number of scans to examine to help determine the best source to add to a geodetic block

Options: Any integer, but values above around 6 are highly recommended

Default: 100

Usage: Only one value used for the whole observation

Example: geoback=10

GEOHIEL

When selecting the initial sources (up to about 3/4 of the total) in a geodetic sequence, SCHED tries to find one that are especially low or high at some stations. GEOHIEL sets the lower bound of the region considered to be high. The related parameter GEOLOWEL sets the upper bound to the “low” region. The default GEOHIEL of 40 degrees has a SecZ of 1.55. Going higher increases slew times without all that much gain in SecZ.

Argument: Any real number

Options: This is an elevation in degrees. It should be between 0.0 and 90.0

Default: 40.0

Usage: Only one value used for the whole observation

Example: geohiel=53.4

GEOLOWEL

When selecting the initial sources (up to about 3/4 of the total) in a geodetic sequence, SCHED tries to find one that are especially low or high at some stations. GEOLOWEL sets the upper bound of the region considered to be low. OPMINEL sets the lower bound. The related parameter GEOHIEL sets the lower bound to the “high” region. The default GEOLOWEL of 23 degrees has a SecZ of 2.55 which differs by 1.0 from the SecZ of 40 degrees, the default for GEOHIEL.

Argument: Any real number

Options: This is an elevation in degrees. It should be between 0.0 and 90.0

Default: 23.0

Usage: Only one value used for the whole observation

Example: geolowel=20.0

GEOPRT

Specifying GEOPRT (no argument) or GEOPRT = 0 will cause the quality measure and the elevations at all sites for all scans in each trial geodetic sequence to be printed while trying to specify a new sequence. The output will go to sched.runlog. This can be a considerable amount of print and is only recommended when trying to understand what the algorithm is doing. If you are a glutton for punishment, use GEOPRT = 1 or even GEOPRT = 2 to cause a lot of information from the source choosing process to be spewed out. This is likely only useful when debugging the software and won’t make much sense without looking at the code to see what all the numbers are.

Argument: Either none, or a number of which 0, 1, 2 are the only useful ones

Options: No argument, 0, 1, 2

Default: -1 which, like anything below 0 means don’t do it

Usage: One value used from the schedule (the last)

Example: GEOPRT = 0 or simply GEOPRT

GEOSEG

Specifying GEOSEG flags a scan to be converted into a geodetic segment. See the section on insertion of geodetic segments for more details about this capability. The argument of GEOSEG is the total time for the geodetic segment. The duration of each scan in the segment is specified with DWELL. The scan to be converted should have a source specified to keep various checking routines happy, but it is not important what that source is, or even whether it is up. In the construction of the segment, it will be ignored.

Geodetic segments will likely need to be 30 to 40 minutes long to have good coverage at all antennas with multiple low elevation scans. They could be even longer if slow antennas are included. Note that not all antennas will be in all scans.

The sources used for the geodetic segments are specified with GEOSRCS.

Argument: Any time in seconds in the usual formats (hh:mm:ss, mm:ss, sss etc.)

Options: Any time

Default: zero - no geodetic segment to be constructed

Usage: Reverts to zero to avoid building successive segments.

Example: geoseg=30:00 for a 30 minute segment

GEOSLEW

When selecting sources for a geodetic segment, SCHED takes into account both the contribution to a fit for SecZ and the slew time. GEOSLEW controls the relative weight. A value of 1.0 means encourage slews shorter than about 1 minute. A larger value would encourage shorter slews. A larger value introduces a larger penalty for a long source and would encourage shorter slews.

Argument: Any real number

Options: Any number

Default: 1.0 - favors slews of around a minute

Usage: Only one value used for the schedule - the last

Example: geoslew=2.0

GEOSLOW

SCHED can leave stations out of a scan if they get there much later than most stations in order to help increase the number of scans in a geodetic sequence. If the source being checked is important for the slow station, it can be blocked from being selected at this pass so that it can be selected later when the slow station can get there in a more timely manner. The effect of doing this tends to be that the slow antennas get used in roughly every other scan (the slew calculation knows if an antenna has the full time of the previous scan to get where it is going). In the current algorithm, if the station arrives more than GEOSLOW seconds after the third to last antenna to get there, it can be left out. Average and median times have been tried as the reference, but there tend to be issues when not all antennas were in the previous scan.

Argument: Any real number - seconds.

Options: Any number

Default: 40.0

Usage: Only one value used for the schedule - the last

Example: geoslow=30.0

GEOSRCS

GEOSRCS is used to list the sources to consider for automatically inserted geodetic segments. It is array of source names, where the sources need to be in the SCHED source catalogs. Since the geodetic segments are best done with strong, compact calibrators with well known positions, all sources of interest are likely to be in one of the standard SCHED catalogs $SCHED/catalogs/sources.gsfc or $SCHED/catalogs/sources.petrov. Note that some people use an odd source name convention that is the J2000 name but truncated at 8 characters (some software doesn’t like more). As of this writing, those names are only included as aliases in the GSFC catalog. For more information about automatic insertion of geodetic segments, see the section on insertion of geodetic segments and the description of the parameter GEOSEG.

The list in the sample below is the recommended set that is the 295 defining sources of the ICRF2. This would be a good list to use and is the list actually active in the example egdelzn.key, alhough that example shows a couple of other possible lists.

Sample input to SCHED:

! ==========================================================  
! =============  Sources for geodetic segments  ============  
! ==========================================================  
geosrcs=’0002-478’,’0007+106’,’0008-264’,’0010+405’,’0013-005’,’0016+731’,  
        ’0019+058’,’0035+413’,’0048-097’,’0048-427’,’0059+581’,’0104-408’,  
        ’0107-610’,’0109+224’,’0110+495’,’0116-219’,’0119+115’,’0131-522’,  
        ’0133+476’,’0134+311’,’0138-097’,’0151+474’,’0159+723’,’0202+319’,  
        ’0215+015’,’0221+067’,’0230-790’,’0229+131’,’0234-301’,’0235-618’,  
        ’0234+285’,’0237-027’,’0300+470’,’0302-623’,’0302+625’,’0306+102’,  
        ’0308-611’,’0307+380’,’0309+411’,’0322+222’,’0332-403’,’0334-546’,  
        ’0342+147’,’0346-279’,’0358+210’,’0402-362’,’0403-132’,’0405-385’,  
        ’0414-189’,’0420-014’,’0422+004’,’0426+273’,’0430+289’,’0437-454’,  
        ’0440+345’,’0446+112’,’0454-810’,’0454-234’,’0458-020’,’0458+138’,  
        ’0506-612’,’0454+844’,’0506+101’,’0507+179’,’0516-621’,’0515+208’,  
        ’0522-611’,’0524-460’,’0524-485’,’0524+034’,’0529+483’,’0534-611’,  
        ’0534-340’,’0537-441’,’0536+145’,’0537-286’,’0544+273’,’0549-575’,  
        ’0552+398’,’0556+238’,’0600+177’,’0642+449’,’0646-306’,’0648-165’,  
        ’0656+082’,’0657+172’,’0707+476’,’0716+714’,’0722+145’,’0718+792’,  
        ’0727-115’,’0736+017’,’0738+491’,’0743-006’,’0743+259’,’0745+241’,  
        ’0748+126’,’0759+183’,’0800+618’,’0805+046’,’0804+499’,’0805+410’,  
        ’0808+019’,’0812+367’,’0814+425’,’0823+033’,’0827+243’,’0834-201’,  
        ’0851+202’,’0854-108’,’0912+029’,’0920-397’,’0920+390’,’0925-203’,  
        ’0949+354’,’0955+476’,’0955+326’,’0954+658’,’1004-500’,’1012+232’,  
        ’1013+054’,’1014+615’,’1015+359’,’1022-665’,’1022+194’,’1030+415’,  
        ’1030+074’,’1034-374’,’1034-293’,’1038+52A’,’1039+811’,’1042+071’,  
        ’1045-188’,’1049+215’,’1053+815’,’1055+018’,’1101-536’,’1101+384’,  
        ’1111+149’,’1123+264’,’1124-186’,’1128+385’,’1130+009’,’1133-032’,  
        ’1143-696’,’1144+402’,’1144-379’,’1145-071’,’1147+245’,’1149-084’,  
        ’1156-663’,’1156+295’,’1213-172’,’1215+303’,’1219+044’,’1221+809’,  
        ’1226+373’,’1236+077’,’1240+381’,’1243-072’,’1244-255’,’1252+119’,  
        ’1251-713’,’1300+580’,’1308+328’,’1313-333’,’1324+224’,’1325-558’,  
        ’1334-127’,’1342+662’,’1342+663’,’1349-439’,’1351-018’,’1354-152’,  
        ’1357+769’,’1406-076’,’1418+546’,’1417+385’,’1420-679’,’1423+146’,  
        ’1424-418’,’1432+200’,’1443-162’,’1448-648’,’1451-400’,’1456+044’,  
        ’1459+480’,’1502+106’,’1502+036’,’1504+377’,’1508+572’,’1510-089’,  
        ’1511-100’,’1514+197’,’1520+437’,’1519-273’,’1546+027’,’1548+056’,  
        ’1555+001’,’1554-643’,’1557+032’,’1604-333’,’1606+106’,’1611-710’,  
        ’1614+051’,’1617+229’,’1619-680’,’1622-253’,’1624-617’,’1637+574’,  
        ’1638+398’,’1639+230’,’1642+690’,’1633-810’,’1657-261’,’1657-562’,  
        ’1659-621’,’1705+018’,’1706-174’,’1717+178’,’1726+455’,’1730-130’,  
        ’1725-795’,’1732+389’,’1738+499’,’1738+476’,’1741-038’,’1743+173’,  
        ’1745+624’,’1749+096’,’1751+288’,’1754+155’,’1758+388’,’1803+784’,  
        ’1800+440’,’1758-651’,’1806-458’,’1815-553’,’1823+689’,’1823+568’,  
        ’1824-582’,’1831-711’,’1842+681’,’1846+322’,’1849+670’,’1908-201’,  
        ’1920-211’,’1921-293’,’1925-610’,’1929+226’,’1933-400’,’1936-155’,  
        ’1935-692’,’1954+513’,’1954-388’,’1958-179’,’2000+472’,’2002-375’,  
        ’2008-159’,’2029+121’,’2052-474’,’2059+034’,’2106+143’,’2106-413’,  
        ’2113+293’,’2123-463’,’2126-158’,’2131-021’,’2136+141’,’2142-758’,  
        ’2150+173’,’2204-540’,’2209+236’,’2220-351’,’2223-052’,’2227-088’,  
        ’2229+695’,’2232-488’,’2236-572’,’2244-372’,’2245-328’,’2250+194’,  
        ’2254+074’,’2255-282’,’2300-683’,’2318+049’,’2326-477’,’2333-415’,  
        ’2344-514’,’2351-154’,’2353-686’,’2355-534’,’2355-106’,’2356+385’,  
        ’2357-318’  

Argument: Up to 400 source names. That can be adjusted if more are needed

Options: Any valid source names.

Default: No sources

Usage: One list used, the last

Example: See above text

GEOSREP

SCHED resists scheduling a given source more than once in a geodetic sequence. But sometimes it is worth doing that when there are limited low elevation options. GEOSREP can be used to set the minimum number of scans after an observation in a geodetic block that a source can be observed again. The default is high enough to normally prevent repeats. A lower value will allow repeats.

Argument: Any integer.

Options: Any, although negative and zero don’t make much sense.

Default: 40.0

Usage: Only one value used for the schedule - the last

Example: geosrep=6

GEOTRIES

The selection of sources for a geodetic segment is based on constructing several possible geodetic sequences and choosing the best. The first few selected sources for each tested segment are chosen randomly from among those that can contribute to the low elevation scans at at least one station. After those, the program chooses the source that best complements those chosen so far in terms of improving the quality measure without excessive slewing. Parameter GEOTRIES sets the number of trial segments to construct and test. The algorithm for making segments comes up with reasonable ones most of the time, so it is not generally necessary to test very many. The algorithm is also moderately slow which will encourage not testing too many. The default is 10 which seems reasonable.

Argument: Any integer 1 or above.

Options: Any

Default: 10

Usage: One value used, the last

Example: GEOTRIES=25

Argument: Either none, or a number of which 0 and 1 are the only useful ones

Options: No argument, 0, or 1

Default: -1 which, like anything besides 0 or 1, means don’t do it

Usage: One value used from the schedule (the last)

Example: GEOPRT = 0 or simply GEOPRT

GRABTO

This is an eVLBI control parameter. Be warned: eVLBI support is under development. The eVLBI parameters are GRABTO, GRABTIME, GRABGAP, and DATAPATH.

GRABTO is used to help control sending of small amounts of previously recorded data over the net. That process happens after the scan of interest, which was recorded normally. The data can either be copied first to the system disk, then transferred later by, for example, ftp or some other protocol GRABTO=FILE. Or the data can be sent directly to the net GRABTO=NET from the VLBI disks. It seems that GRABTO=NET is not valid for systems controlled by the Field System (eg MarkIV and variants).

This is different from the real time transfer controlled by DATAPATH.

If GRABTO is NONE, which is the default, no data will be written and the other GRAB.. parameters will be ignored.

Note that GRABTIME determines what segment of data is sent. GRABGAP determines what amount of time needs to be set aside to grab the data from the VLBI disk (ftp transfer can happen during the next scan).

Argument: Character string of up to 4 characters.

Options: NET for direct transfer to external network. FILE for transfer to the control computer system disk. NONE Do not transfer the data anywhere.

Default: NONE

Usage: A value for each scan. Defaults to previous scan. Be sure to set back to ’NONE’ after a grab scan.

Example: GRABTO = ’FILE’

GRABTIME

This is an eVLBI control parameter. Be warned: eVLBI support is under development. The eVLBI parameters are GRABTO, GRABTIME, GRABGAP, and DATAPATH.

GRABTIME determines which part of a scan will be used for eVLBI. There are 2 arguments. The first gives the duration in seconds of the data to be sent. The second argument gives the seconds before the end of the current scan that the grabbed data will end. Thus the data to be sent are from the interval from GRABTIME(1) + GRABTIME(2) to GRABTIME(2) seconds before the end of the scan.

Argument: Two real numbers — times in seconds.

Options: Any times.

Default: 30,0. Which means transfer the last 30 seconds of the scan

Usage: Values for each scan. Defaults to previous scan.

Example: GRABTIME = 30,0

GRABGAP

This is an eVLBI control parameter. Be warned: eVLBI support is under development. The eVLBI parameters are GRABTO, GRABTIME, GRABGAP, and DATAPATH.

GRABGAP specifies how much time will be needed after the scan to transfer the data. This will initially just be used for checking, and maybe for some optimization functions. Eventually it may have other uses.

Argument: Two real number — time in seconds.

Options: Any time.

Default: 5.0 + GRABTIME(1)*bitrate/110Mbps

Usage: Value for each scan. Defaults to previous scan.

Example: GRABGAP = 90

GRIDMIN

GRIDMIN is the inner radius of the grid used for UV coverage optimization. It is in the units of the UV plot. See the section on Configuration Studies for details. This is only used when OBSTYPE=CONFIG.

Argument: Any number, typically a value similar to the array’s shortest baseline.

Options: Any value.

Default: 25.0 (km for NMA studies)

Usage: Only last one used

Example: GRIDMIN = 10.0

GRIDMAX

GRIDMAX is the outer radius of the grid used for UV coverage optimization. It is in the units of the UV plot. See the section on Configuration Studies for details. This is only used when OBSTYPE=CONFIG.

Argument: Any number, typically a value similar to the array’s shortest baseline.

Options: Any value.

Default: 250.0 (km for NMA studies)

Usage: Only last one used

Example: GRIDMAX = 350.0

GRIDMEAS

GRIDMEAS is used to choose between quality measures to use when rating arrays using the UV coverage on the grid specified with the other “GRID” parameters. The options are COUNT, which simply counts the number of sampled cells, and RMS, which determines the RMS of the number of samples per cell.

Argument: COUNT or RMS

Options: Only one of the above two options

Default: COUNT

Usage: Only last value used

Example: GRIDMEAS = ’COUNT’

GRIDNR

GRIDNR is the number of radial cells in the grid used for UV coverage optimization. See the section on Configuration Studies for details. This is only used when OBSTYPE=CONFIG.

Argument: Any integer. About 40 can be a reasonable choice.

Options: Any value. (non-integers will be truncated.)

Default: 20

Usage: Only last one used

Example: GRIDNR = 40

GRIDNT

GRIDNT is the number of azimuthal cells in the grid used for UV coverage optimization. See the section on Configuration Studies for details. This is only used when OBSTYPE=CONFIG.

Argument: Any integer. About 72 can be a reasonable choice.

Options: Any value. Non-integers will be truncated.

Default: 36

Usage: Only last one used

Example: GRIDNT = 72

GRIDSTEP

When doing configuration studies, if key S is pressed, SCHED will calculate the array quality measure for points on a grid in latitude and longitude centered on the first highlighted (red) station. It is best to only highlight one. Then labeled contours will be plotted over the region of the calculation. Note that the contours are not cleared until the uvcoverages are plotted, so you can end up with several. The contours are reploted (including to an output file) until some action like altering a any station’s selection status or moving a station is done. The spacing of grid points in latitude and longitude for calculating the quality is given in arcminutes by GRIDSTEP.

Argument: A number in arcminutes of latitude and longitude for the spacing of station locations used to make a contour map of quality measure

Options: Any real number

Default: 3.0 - three arcminutes

Usage: Only last one used

Example: GRIDSTEP = 6.0

GRIDVLA

When doing configuration studies, only use baselines to the VLA to calculate the quality measure. This is useful for the NMA which will have large swatches of baselines to the VLA. Those swatches dominate the sensitivity.

Argument: No argument to set. Any non-zero number will unset.

Options: Any number, but none needed (logical)

Default: Not set (will use baselines to VLA antennas)

Usage: Only last one used

Example: GRIDVLA

GRIDW0

GRIDW0 is the approximate radius of the transition from linear to logarithmic radial grid sizes in the grid used for UV coverage optimization. It is in the units of the UV plot. See the section on Configuration Studies for details. This is only used when OBSTYPE=CONFIG.

Argument: Any number, typically a value at about 0.1 to 0.3 of the array’s longest baselines

Options: Any value.

Default: 0.0 (results in a pure logarithmic grid)

Usage: Only last one used

Example: GRIDW0 = 45.0

GROUP

SCHED has the ability to accept loops through scans. The two parameters that allow this are GROUP and REPEAT. They should be specified along with the parameters of the first scan in the loop. GROUP specifies the number of scans to be involved in a loop. REPEAT specifies how many times to go around the loop. Any start or stop times specified for the scans of the loop will only apply to the first pass. DURation or DWELL should be used to set the scan lengths.

Argument: Integer.

Options: Any.

Default: Not used.

Usage: Reverts to not being used if not specified for a scan.

Example: GROUP=2

HIGROUP

HIGROUP is used in conjunction with OPTMODE = ’HIGHEL’. If HIGROUP is set to greater than 1 for a scan while PTMODE = ’HIGHEL’, a number of scans specified by HIGROUP, including the one where it is specified, are checked for elevation. The single scan with the highest elevation is used. This aids in picking sources for calibrators, pointing scans etc what are best for a schedule whose run time might be set just before the observations.

Argument: Integer.

Options: Any.

Default: Not used.

Usage: Reverts to not grouping scans.

Example: HIGROUP=6

IATUTC

Obsolete parameter now that the VLA is no longer using observe decks.

IATUTC sets the value of IAT-UTC. This is about 30 seconds now. This is only used if “//PM” cards are needed for the VLA since the zero-offset epoch must then be specified in IAT. SCHED does not use IAT for anything else. If not specified, the default is the value from the SLA library which should be ok, as long as that routine is maintained.

Argument: An integer number of seconds.

Options: Any integer - should be correct value.

Default: Value from SLA_DAT, which should be correct.

Usage: Only one value accepted, the last.

Example: IATUTC=29

INTENTs

INTENTs is used to provide a series of text strings that give guidance to various stages of data handling. They can be directives to telescopes to, for example, do active phasing at the VLA or hold the previous phase. They could be used by the correlator. Or they can be used to tell pipeline processing that a scan is to be used for one or more specific types of calibration. For now, the intents are written to the VEX file as comments with the scans.

The arguments of INTENTs are up to 25 strings of up to 80 characters each. Note that each string should be in quotes and they should be separated by commas. If the line ends with a comma, the next line can be used for the next string. If no INTENTs are given, they default to the previous scan. If any are given, they all return to blank unless given again again. If NONE is specified, all intents are cleared.

SCHED does not parse most INTENTs. But some, especially related to the VLA phasing, are recognized and appropriate actions are taken.

An intent may be made to target a specific antenna by starting with the station name followed by a colon. Use the same station name as used in the station catalog. If no station name is given, the INTENTs will be assumed to apply to all stations for which it is meaningful. An example line with a station might address asking the VLA to phase but not some other interferometer with: INTENT = ’VLA:AUTOPHASE_DETERMINE’.

Some established values of INTENTs in the VLA environment are listed here. Also some requested for other instruments are listed. Most will not be used in VLBI schedules. A VLBI specific list has not been generated. Of interest for the VLA are DETERMINE_AUTOPHASE and DETERMINE_OFFSET_POINTING.

OBSERVE_TARGET

CALIBRATE_BANDPASS

CALIBRATE_FLUX_DENSITY_SCALE

CALIBRATE_COMPLEX_GAIN

CALIBRATE_POLARIZATION_ANGLE

CALIBRATE_POLARIZATION_LEAKAGE

CALIBRATE_ABSOLUTE_POSITION

CALIBRATE_OFFSET_POINTING

DETERMINE_AUTOPHASE

DETERMINE_RFI

CALIBRATE_DELAY

FIND_FRINGE

DETERMINE_ANTENNA_GLOBAL_POINTING_MODEL

MAP_ANTENNA_SURFACE

CALIBRATE_FOCUS

DETERMINE_SINGLE_DISH_POINTING

DETERMINE_OPACITY_TIPPING_STYLE

OBSERVE_PULSAR

TIME_PULSAR

SetAtnGain

OTHER

This above list is from VLA documentation. For VLBI, the following are also used, although the preferred method of creating them is through the VLAMODE and VLAPEAK parameters. SCHED will not allow mixing methods of specifying these aspects of the observing.

AUTOPHASE_DETERMINE to apply the phasing offsets.

AUTOPHASE_APPLY to apply the phasing offsets.

AUTOPHASE_OFF to not apply any phasing offsets.

REFERENCE_POINTING_DETERMINE

REFERENCE_POINTING_ADJUST

REFERENCE_POINTING_APPLY

REFERENCE_POINTING_OFF

Argument: Up to 25 character strings of up to 80 characters each. Can use separate lines as long as the preceding line ends in a comma.

Options: Any strings. ’NONE’ clears all INTENTs’

Default: Blank

Usage: All INTENTs keep the last value if none are specified. If any are specified, all are initialized to blank, and must be respecified if still desired.

Example: intent = ’DETERMINE_AUTOPHASE’, ’CALIBRATE_BANDPASS’ or intent=VLA:SetAtnGain

LINEINIT

LINEINIT indicates that the next few keyin input groups are rest frequency specifications for spectral line observations. See Section 2.5 for details. LINEINIT should not be mixed with other indicaters of in-stream data such as SRCCAT, STACAT, SETINIT, or TAPEINI. If LINEINIT is found, the end of the input group (everything up to the “/”) is not considered the end of inputs for this file. The next inputs after the line data are entered will continue to apply to the current file (usually the first).

Argument: None.

Options: None.

Default: Not set.

Usage: Should only be given once in schedule.

Example: LINEINIT /

LINENAME

LINENAME gives the name of the rest frequency group to use for this scan. The rest frequencies and names are specified in the LINEINIT input. See Section 2.5 for details.

Argument: A name of up to 8 characters.

Options: Must be one of the names in the LINEINIT input.

Default: Must use if DOPPLER set.

Usage: Reverts to previous scan.

Example: LINENAME=’OH1665’

LINEPG

LINEPG is the number of lines on a page for the operator schedule files and summary files.

Argument: Integer.

Options: Any.

Default: 55

Usage: Only one value used.

Example: LINEPG=60

LOCFILE

LOCFILE gives the name of an auxillary file to the stations catalog that can contain the station positions. All parameters that can be specified in the LOCFILE can be specified directly in the station catalog and are documented along with that catalog. The station locations used in the default catalogs are from the VLBA correlator data base and are maintained in a very different way from the rest of the information in the station catalog, so it is convenient to have them in a separate file. If a user is making their own catalog, they could put all the information in the station catalog as indeed they must if putting the information into the main schedule through STACAT.

LOCFILE defaults to the standard file distributed with SCHED. If the file is not found, a complaint will only be generated if a stations in the station catalog is missing a position.

Only a subset of the stations catalog parameters can be put in the LOCFILE. They are X, Y, Z, DXDT, DYDT, DZDT, EPOCH, AXISTYPE, and AXISOFF. All other station information must be in the main stations catalog. In addition to these parameters, a catalog version number (VERSION), a station name (DBNAME), and a station code (DBCODE), that might be different from those used in the main stations catalog, should be included. The desired locations catalog entry is identified by giving a matching DBNAME or DBCODE in the main stations catalog to point to the locations catalog entry. The use of different names and codes is an artifact of the use of position information from the geodetic groups which use different station names from those typically used in astronomy. Also the locations file generally contains a separate entry for each pad of an interferometer such as the VLA which is not the case for the stations catalog.

Argument: A file name of up to 80 characters.

Options: Any valid file name or none.

Default: $SCHED/catalogs/locations.dat

Usage: Only specify once.

Example: LOCFILE=’/users/cwalker/sched/locations.dat’

LST

LST causes SCHED to assume that all input times are in local sidereal time. If no argument is given, the “local” refers to the VLA. Otherwise, a station name can be given to allow scheduling in lst for some other station.

When LST is specified, there are two ways to specify the date. DAY can be used to specify the (modified?) local sidereal day number as found on the VLA monthly schedules. If this is done, YEAR and MONTH are ignored. SCHED senses this situation by testing for a day number larger than the length of a year. The other option is to specify the calendar date in the usual way ( YEAR, MONTH, DAY). In this case, SCHED will figure out when on that calendar day the local sidereal time specified for a scan occurs. With this option there is a period of a bit less than 4 minutes each day when the specification is ambiguous (sidereal days are shorter than UT days). If that situation is encountered, SCHED will abort with a request to choose the desired local sidereal day — the options will be shown.

This parameter was originally intended mainly for VLA-only scheduling. But it is now also used for dynamic scheduling on the VLBA.

When LST is selected, most times are sidereal times or intervals. These include START, STOP, DURation, and DWELL, but not PRESCAN, MINPAUSE, or PRESTART.

Argument: Text of up to 8 characters giving the station name.

Options: Any.

Default: Not used if not given. ’VLA’ if given without argument.

Usage: Only one value used.

Example: LST=’VLBA_PT’

MAPLIM

MAPLIM is used to provide the longitude and latitude limits for the plot that is made when ( OBSTYPE is set to CONFIG and there are more than one source. This is a special mode mainly for array configuration studies. The 4 values are the longitude minimum and maximum followed by the latitude minimum and maximum, all in degrees. The system is such that North America is at positive longitudes, which is backwards from some schemes.

Argument: Four numbers.

Options: Any.

Default: Use numbers appropriate for NMA configuration study.

Usage: Only one value used.

Example: MAPLIM=80.0, 140.0, 15.0, 50.0

MINPAUSE

MINPAUSE is used to specify the minimum time a recording will be stopped between scans. Its effects are basically ignored by the wideband systems (RDBE, WIDAR with MARK5C recording) on the VLBA, VLA GBT, EB_VLBA and perhaps others so users of those systems can ignore the parameter, taking the default of zero.

The topic of controlling scan timing is discussed in detail in the Scan Times section.

If the interval between scans is shorter than the minimum specified with MINPAUSE, the recording will be be kept going between the scans. The need to prevent the recording from stopping for a short interval was most pronounced with tapes which took several seconds to accelerate and decelerate. With disks, that is not an issue so the only reason would be if there is a finite time to get the recording organized and the playback synchronized. Those are issues, at a low level with the Mark5A systems, but not with the Mark5C, which is in use and will become the dominant recording during 2013. With Mark5C, MINPAUSE should be set to a very small value or zero. Zero is the default for all systems except the legacy VLBA DAR and anything controlled by the Field System (may change for the DBBC). For the exceptions, 10 seconds is used.

For the VLA and sites with the VLBA control system, the recordings are started at the data-good time as reflected in the individual station lines of the VEX file. Those times account for any antenna slew and the additional time requested through TSETTLE and other such parameter in the station catalog. MINPAUSE only affects the media start time which is the nominal start time minus PRESTART, not the data good time, so it is basically ignored for such VLBA and VLA

MINPAUSE can be specified for each scan, but usually will be set to one value for the whole schedule. If the media start of a scan is less than MINPAUSE (seconds) from the end of the last recording scan, the recording will be left running between the scans. This action is station dependent — different stations can have the recording started at different times except when writing a VEX file, in which case simultaneity is enforced. The nominal start time of the scan as displayed in the summary is not affected by MINPAUSE. You can use the option TPSTART in the SUMITEM list to display in the summary how long before the scan start time the recording starts. The recording start time is also given in the sch file.

MINPAUSE is mainly used now to prevent excessive recording scans on the Mark5A system. The system does not allow more than 1024 data scans on the disks. There is one scan for each period during which the recording does not stop, regardless of the number of source scans during that period. This limitation can be an issue with large disk packs and fast-switching phase-referencing projects. The default value is meant to prevent recording stops during fast switching.

While too many recording scans are a problem, so are too few. If something goes wrong with playback, the correlators cannot recover until the start of the next recording scan. Thus it is not wise to have recording scans more than about an hour long. Note that the MarkIV systems will not stop the recording for gaps of less than 10 seconds so a gap inserted to break a recording scan should be longer than that.

Short recorder stoppages could cause problems for playback in the era of tapes. Every time the recording stopped, it must be resynced, which takes 10-20 seconds for the old VLBA hardware correlator. This is not much of an issue for the DiFX software correlator or the MarkIV correlators.

There are a variety of ways to prevent recordings from being stopped between scans. The simplest is to schedule using DUR or explicit times with no specification of an interval between scans. In such cases, SCHED will not schedule any sort of pause in scans or recordings. One can use MINPAUSE to keep the recording going through short gaps. For longer gaps when using MINPAUSE, the recording start time will not be affected. PRESTART (or a negative value for the old parameter PRESCAN) can be used to shift the scan start time forward from the time set by other criteria (such as antennas on-source when using DWELL). The start time is moved by the same amount for all stations and is not moved past the stop time of the most recent scan at any station.

For PCFS (VEX) controlled stations, the user should bear in mind that all start times currently (Oct. 2001) must be equal. SCHED will issue a warning if this condition is violated and will try to synchronize recording starts when using MINPAUSE.

In the tape era, it was possible for MINPAUSE to confound your attempts to leave gaps required by VEX files for tape reversals. In such cases, you would need to adjust MINPAUSE on the offending scans. The default should not cause this problem because it does not request continuous tape motion through scans long enough to keep the VEX check routines happy for a reversal.

Note that MINPAUSE used to be multiplied by the speedup factor to determine the actual length of a pause at record time. That made it actually a time of the pause at playback time on the old VLBA correlator. That concept is no long relevant so the multiplication by the speedup factor has been removed.

Argument: A number giving the minimum recording stoppage in seconds.

Options: Any number.

Default: 10 seconds for legacy systems and anything controlled by the Field System. It is 0 for anything else including the VLBA/RDBE and VLA/WIDAR systems.

Usage: Defaults to previous scan.

Example: MINPAUSE=30

MONTH

MONTH is the month of the stop time of the scan. The day of year of the first day of the MONTH, minus 1, is added to the value for SCHED parameter DAY to get the day of year of the project. Thus MONTH can be specified and DAY given as the day of the month, or MONTH can be left at the default of 1 and DAY can be given as the Day of Year (DOY). Other combinations are also possible, but don’t make much sense.

Argument: Integer.

Options: Any between 1 and 12.

Default: 1

Usage: Defaults to previous scan.

Example: MONTH=10, meaning October.

NCHAN

NCHAN is an obsolete parameter used in conjunction with FREQ and BW. Now that setup files are required, the number of channels is obtained from them.

NOSETUP

NOSETUP tells SCHED to ignore all setup file handling. This is meant to aid in planning when trying random or hypothetical stations so that a setup file or frequency file entry for such stations is not needed. If this is specified, no telescope control files can be written. However, the plotting section is functional.

If NOSETUP is specified, do not give SUMITEM=TAPE1 or TAPE2.

Argument: None.

Options: Any none zero argument is the same as not specifying it.

Default: Not specified.

Usage: Only one value used per experiment.

Example: nosetup

NOTE1, NOTE2, NOTE3, and NOTE4

NOTE1, NOTE2, NOTE3, and NOTE4 are 128-character text strings that can be used to pass any information in the cover section. Instructions regarding pointing, Tsys measurement, and where to send logs are typically provided this way. Do not use exclamation marks (“!”). They mess up the VLBA system’s ability to parse the control files. SCHED will die if you try.

Argument: Each of the 4 parameters takes a character string of up to 128 characters.

Options: Any text.

Default: Blank

Usage: Uses only one value, the last.

Example: NOTE1=’Please measure Tsys for every scan.’

OBSMODE

OBSMODE gives basic information on the technical nature of the project. The receiver wavelength and the recording system to be used should be noted. Any non-standard setup should be noted here, and expanded on with NOTE1, etc. This is for the cover information.

Argument: Text of up to 58 characters.

Options: Any - include receiver wavelength and recording system.

Default: Blank

Usage: Only one value used, the last.

Example: OBSMODE=’6cm Mark II Standard Network setup’

OBSPHONE

OBSPHONE is the phone number for Principal Investigator during the observations for the cover information.

Argument: Text of up to 49 characters.

Options: Any - usually a telephone number.

Default: Blank

Usage: Only one value used, the last.

Example: OBSPHONE=’+1-505-835-7392’

OBSTYPE

OBSTYPE tells SCHED what type of observation this project is. There are really only four options, although there are several ways to specify most of them. They are:

Mark II.
Specifying either OBSTYPE = MKII or MARKII causes SCHED to assume that the Mark II recording system will be used. This system is now obsolete, although maybe not totally gone, so this should not be common. It causes tape change requests to occur at time intervals specified by AUTOTAPE and assumes the Mark II tape is to be left running.
Wide band recordings.
Specifying VLBI, VLBA, MKIII or MKIV causes SCHED to assume that the wide band recorders (tape or disk) are in use. For the wide band recording modes, the necessary information on tape speed, passes per index position, etc., is taken from the setup file and the TAPEFILE and the type of recorder to use is based on the station catalog and the TAPEFILE parameter MEDIA. If there is a gap between the stop time of one scan and the start time of tape motion in the next (after taking into account START, DWELL, GAP, and PRESCAN), then SCHED will insert a dummy scan with no tape motion (or possibly a rewind or fast-forward) during this gap. Note that there is no requirement that the FORMAT in the setup file match which OBSTYP is specified. In fact, it is allowed to mix types at different stations. For historical reasons, VLBA, MKIII, MKIV, MARKIII and MARKIV are allowed alternatives with the same effect as VLBI and some of these appear in the examples.

SCHED does not support Mark III recordings on other than VLBA systems — the snap output contains no tape commands. In any case, Mark III is obsolete and no longer in use.

Pure VLA observations.
If OBSTYPE = VLA, SCHED will assume that only the VLA is being scheduled and that VLBI recorder setup or commands are required. This is the mode in which SCHED can be used for many types of VLA scheduling. With the advent of the EVLA project, SCHED should no longer be used for scheduling pure VLA projects so this option is basically obsolete.
Single dish observing.
OBSTYPE = NONE or PTVLBA (the default) causes recorder handling to be ignored. This is mainly for VLBA single dish pointing observations. This does set up the channels in the Data Aquisition System (BBCs, IF distributers etc), but does not record VLBI data.
Configuration studies.
OBSTYPE = CONFIG causes a map of station locations to be plotted when plotting uv coverage for multiple sources. This is mainly for array design configuration studies. The axis limits are set with parameter MAPLIM and default to values appropriate for NMA configuration studies. Continental, national, US state, and New Mexico roads will also be plotted if the vector files are available in $PLANET_DATA as they are in Socorro. If you want to use this capability, you might wish to contact Craig Walker about details and help — it is not really meant for general use.

Argument: Text of up to 8 characters, not case sensitive.

Options: MKII, MARKII, VLBI, VLBA, MKIII, MARKIII, MKIV, MARKIV, VLA, PTVLBA, CONFIG, or NONE.

Default: NONE

Usage: Only one value used per project.

Example: OBSTYPE=MKIII

OPDUR

OPDUR is the total duration of project being scheduled with an optimizing mode. Some of the optimizing modes keep generating new scans until they run out of time scheduled for the project. This parameters informs SCHED of the total project duration.

Note that the optimizing modes are somewhat experimental. If they are used, the output schedule should be checked carefully.

Argument: A time in time format (eg hh:mm:ss)

Options: Any time that is to be used as the length of the project.

Default: 0

Usage: Only one value used per project

Example: OPDUR = 13:30:00

OPELPRIO

OPELPRIO is used to specify two elevation ranges (4 values) to give high priority when optimizing a schedule. With OPTMODE=SCANS, scans on a source that falls within these elevation ranges will be taken every time while scans falling outside these ranges at all stations may be skipped depending on the setting of OPSKIP and on what happened on previous opportunities to observe the source. For geodesy projects, for example, priority might be given to very low elevations (for atmospheric determination) and very high elevations (to get good leverage on the parameter fits).

Note that the optimizing modes are somewhat experimental. If they are used, the output schedule should be checked carefully.

Argument: Four real numbers to be interpreted as elevations in degrees.

Options: Any valid elevation (0 to 90 degrees)

Default: All zero.

Usage: Only one set of values, the last, used for the project.

Example: OPELPRIO = 2., 15., 75., 90.

OPHA

OPHA is the parameter for OPTMODE=HAS that sets the desired hour angle at the reference station OPHASTA for this scan. If this parameter is not set, SCHED figures out how many scans there are on the source, when the source can first be seen (either because of elevation limits or experiment start time) and when it can last be seen. It then spaces the desired observation times evenly between those times.

The weight based on deviation from the desired hour angle is calculated using the formula:

  TIMEWT=OPHAWT(JSCN)*(0.5+(1.0/PI)*  
           ATAN(1.5*(TAPPROX-OPHAT(JSCN))/ OPHAWIDT(JSCN)))

where OPHAT is OPHA converted to a time, TAPPROX is the proposed observe time of the next scan, and OPHAWT and OPHAWIDT are other SCHED input parameters. Note TAPPROX is likely to be adjusted slightly once the scan is chosen and full account of slew times is taken.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

OPHMAXDT

OPHMAXDT is the parameter for OPTMODE=HAS that sets the maximum deviation from the desired hour angle that a scan will be considered. This helps limit the number of scans considered at any one time but, most importantly, prevents use of the scan at an inappropriate time, for example, because no appropriate scan was available at that time. Because of this parameter and OPDUR is is possible to not use all input scans. Users should watch for this and probably adjust scan parameters to fix the problem.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real time

Options: Any

Default: 2:0:0 (2 hours)

Usage: Uses the most recent value specified.

Example: OPHMAXDT = 30:00

Argument: Any real hour angle

Options: Any

Default: Zero. SCHED will pick the values. The default is usually what you will want.

Usage: Uses the last value specified. It is not a good idea to specify one and not the others as then all scans will have the same desired hour angle and the behavior will probably be a bit weird.

Example: OPHA=PT

OPHAWID

OPHAWID is the parameter for OPTMODE=HAS that sets the normalization time (normal time format) for the tolerance for deviation from the specified hour angle. A larger value allows SCHED to be a more sloppy with placement of the scan.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real time, usually in a format like 30:00 for 30 minutes.

Options: Any positive value

Default: Zero. Set to the spacing between desired scans on the source.

Usage: Uses the most recent value specified.

Example: OPHAWID = 30:00 (for 30 minutes)

OPHAWT

OPHAWT is the parameter for OPTMODE=HAS that sets the relative importance of the deviation from the desired hour angle compared to minimizing slew time or getting a scan near a limit.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real number. But negatives don’t really make sense.

Options: Any

Default: 1.0.

Usage: Uses the most recent value specified.

Example: OPHAWT = 3.5

OPHASTA

OPHASTA is the parameter for OPTMODE=HAS that sets the reference station at which hour angles are calculated. It is usually best to choose a station in the middle of the array, such as Pie Town (VLBA_PT or PT) for the VLBA.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: A station name or station code matching a scheduled station.

Options: Any valid station in the schedule

Default: PT

Usage: Uses the one value for the experiment - the last specified.

Example: OPHASTA = VLBA_LA

OPHLIMTI

OPHLIMTI is the parameter for OPTMODE=HAS that sets the normalization for the time offset from the limits of when a source is up. The equations for the weights for rise and set are:

  RISEWT=MAX(0.0,OPHLIMWT(JSCN)*(1.0-ABS(HA1(JSCN,RSTA)-HAMIN(JSCN))*  
             3600.0/OPHLIMTI(JSCN)))  
  SETWT=MAX(0.0,OPHLIMWT(JSCN)*(1.0-ABS(HA1(JSCN,RSTA)-HAMAX(JSCN))*  
             3600.0/OPHLIMTI(JSCN)))

where HA1 is the hour angle of the proposed scan, HAMIN and HAMAX are the hour angles at which the source rises or sets. This only worries about the rise and set times. Some day it maybe should also worry about experiment start and end.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real hour angle - in seconds.

Options: Any

Default: 1800.0

Usage: Uses the most recent value specified.

Example: OPHLIMTI = 1200.D0

OPHLIMWT

OPHLIMWT is the parameter for OPTMODE=HAS that sets the relative importance of the weighting based on being near the rise or set time of a source. For the equations for these weights, see OPHLIMTI.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real number

Options: Any

Default: Zero.

Usage: Uses the most recent value specified.

Example: OPHLIMWT = 1.0

OPMINSEP

OPMINSEP is the parameter for OPTMODE=HAS that is used to prevent two scans on the same source from being scheduled too close together. SCHED determines the default spacing of scans — evenly spaced across the available time — regardless of whether the user overrides that default by specifying the desired hour angles. That default spacing is multiplied by OPMINSEP to get the minimum separation. Once a scan is scheduled, another scan on that source will not be scheduled until after that minimum separation has passed. A different value can be given for each scan.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real hour angle, although usually a fraction between about 0.0 and 1.0

Options: Any

Default: 0.0 which means don’t have a minimum separation.

Usage: Uses the most recent value specified.

Example: OPMINSEP = 0.4

OPMISS

OPMISS is used to reduce the priority of some sources when using OPTMODE = ’SCANS’. The current scan will only be accepted if the OPMISS scans have been skipped. See OPTMODE for more details.

Argument: Any integer

Options: Any

Default: Zero. No scans will be skipped.

Usage: Uses the last value specified. So if one scan is given a high number, be sure to drop the value for the next.

Example: OPMISS = 7

OPMINEL

OPMINEL specifies the minimum elevation in degrees below which sources will be considered to be “down”. In all modes, if less than OPMINANT antennas are up, the scan will be skipped.

This is used mainly for optimizing modes to help select scans, and for experiment planning in order to, for example, plot the uv coverage available if all low elevation data and all data with less than several antennas will be discarded. The default will have no effect on schedules.

Argument: A real number to be interpreted as an elevation.

Options: Any valid elevation.

Default: 0.0

Usage: On per scan. Defaults to previous scan.

Example: OPMINEL = 15.

OPMINANT

OPMINANT sets minimum number of antennas for which the source must be up for the scan to be accepted. To be up, a source must be above the telescope slew limits, any specified horizon, and above OPMINEL.

This is used mainly for optimizing modes to help select scans, and for experiment planning in order to, for example, plot the uv coverage available if all low elevation data and all data with less than several antennas will be discarded. The default will have no effect on schedules. A separate value can be specified for each scan.

Argument: An integer.

Options: Any

Default: 0

Usage: One per scan. Defaults to previous scan.

Example: OPMINANT = 4

OPNOSUB

OPNOSUB tells the SCHED optimizing modes not to allow subarraying. All antennas are to be scheduled in all scans, regardless of whether the source is up.

Note that the optimizing modes are somewhat experimental. If they are used, the output schedule should be checked carefully.

Argument: None

Options: None

Default: Not set — allow subarraying.

Usage: Only one value used for schedule — the last.

Example: OPNOSUB

OPPRTLEV

OPPRTLEV tells the SCHED optimizing modes how much extra information on the inner workings of the scan choice to print. So far, it is only used for OPTMODE=HAS. See the description in the section on OPTMODE for details.

Argument: A integer.

Options: Useful values are between 0 and 3

Default: 0, which gives only bare summaries.

Usage: Only one value used for schedule — the last.

Example: OPPRTLEV=3

OPSKIP

In optimizing mode “SCANS”, skip each source OPSKIP times after it is last seen, unless it is in the OPELPRIO elevation range. This parameter is not applied to pointing (and Ta and PN3DB) observations when they are mixed with other types of scheduling. It is always applied when OBSTYPE is NONE or PTVLBA.

Note that the optimizing modes are somewhat experimental, especially this one! If they are used, the output schedule should be checked carefully.

Argument: An integer, usually small.

Options: Any

Default: 0

Usage: Only one value used for schedule — the last.

Example: OPSKIP = 2

OPSLEWTI

OPSLEWTI is the parameter for OPTMODE=HAS that is used to normalize the weighting based on slew time. The slew time weight is set by the equation:

 SLEWWT = MAX(0.0,OPSLEWWT(JSCN)*(1.0-OPSLEW/OPSLEWTI(JSCN)))

Where OPSLEW is the difference between the stop time of the previous scan and the time when all antennas are ready to observe the scan being tested.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real hour angle

Options: Any

Default: Zero.

Usage: Uses the most recent value specified.

Example: OPSLEWTI = 1:0:0

OPSLEWWT

OPSLEWWT is the parameter for OPTMODE=HAS that sets the relative importance of the weight based on slew time compared to the other weights. See OPSLEWWT for the equation used to set the slew weight for a scan.

See the discussion of the possible optimization modes in the section on OPTMODE for more information on OPTMODE=HAS

Argument: Any real number. Positive is best.

Options: Any

Default: Zero. Don’t pay attention to slew times.

Usage: Uses the most recent value specified.

Example: OPSLEWWT = 1.0

OPTMODE

OPTMODE sets the optimization mode. The valid modes are:

NONE.
This is the default. The input schedule will be used as specified.
SCANS.
For this mode, the schedule will be followed as specified. However only scans with more than OPMINANT antennas with the source up (above the horizon and within the slew limits) and above OPMINEL will be accepted. For each accepted scan only those antennas that are up and above OPMINEL will be scheduled unless OPNOSUB is specified. DWELL would normally be specified to allow for slews. Subarraying will happen if two successive sources can only be seen by different antennas since the optimization keeps track of the previous scan on a per-antenna basis.

The usual way to use this mode is to specify a loop containing all the desired sources (and frequencies etc.) and lasting longer than the desired total time. Then the optimization will pick the scans that make sense and will quit after OPDUR. This mode is especially useful for scheduling pointing observations.

There is a trick available, triggered by OPSKIP, that is an attempt to emphasize scans in desirable elevation ranges (set by OPELPRIO. If a loop is used, this will cause scans to be skipped OPSKIP times before they are used again unless they are in the desired elevation ranges.

There is another trick to give low priority to some scans using OPMISS. The current scan will only be accepted if at least OPMISS preceding scans in a row have been missed. If, for example, you have a loop of scans, as is typical in pointing schedules, and you have one that you only want to have used if all others are unacceptable (eg too low), then set OPMISS to the length of the loop.

CELLS.
For this mode, the input scan list is treated as a pool of possible scans. The sky over each antenna is divided into 9 cells (3 X 3 in Az and El) and the time that each cell was sampled is recorded. For each output scan, all input scans are checked for which cells they sample and a weight is calculated based on the time since the last time that cell was sampled. The weight is adjusted to discourage long slews with the characteristic time scale of that discouragement set by OPTSLEW in minutes. Also, if some low elevation cells for a station have not been sampled in a long time (characteristic time scale set by OPTLOWT, the weight for other low elevation cells will be increased. This tries to compensate for edge stations that have no mutual visibility with the rest of the array for sources at low elevation in certain directions. The input scan to use is then selected based on the adjusted weights.

This mode is an attempt to provide a mechanism for scheduling geodetic type observations. Parameters OPMINANT, OPMINEL, OPDUR, and OPNOSUB have the same meanings for CELLS mode as for SCANS. The CSUB mode is able to do almost the same thing as this mode plus it handles subarraying. It may eventually completely replace the CELLS mode.

CSUB.
This mode is much like the CELLS mode except that it uses subarrays. The sky over each antenna is divided into 9 cells. For each possible pair or sources, a scan is constructed with each antenna observing the source for which the priority is highest. The priority is the result of the time since the cell the source is in was sampled adjusted to downweight long slews (OPTSLEW) and upweight low elevation scans when other low elevation cells are not being sampled (OPTLOWT). If the minimum number of antennas per scan ( OPMINANT) is not satisfied, some are shifted so that it is. Then the subarrayed scan is compared with single source scans with each of the two sources and the best option chosen. There is a weighting factor which favors the single source cases and has been adjusted so that something less than half the scans include all stations. Some day this should be made an input parameter. Finally, if there are more than 2 antennas left over, they are put in a third subarray with an optimized source.

Like the CELLS mode, this mode is for geodetic type observations. Various parameters have the same meaning here as for the other modes except that OPNOSUB is not allowed since it doesn’t make sense. Also, OPMINANT is a goal. The third subarray can have less as can one of the other two under certain very special circumstances.

UPTIME.
This mode is designed for experiment planning. For each input scan, it creates a string of scans of duration DUR or DWELL, spaced by GAP (helps interpret UV plots), and lasting for total time OPDUR. All such series of scans start at the start time of the first scan. Usually (OPDUR=24:00:00) would be used to examine a whole day or the actual start time and total duration of allocated time would be used. Each input scan would normally be on a different source. Note that this mode gives a backward time jump at the first scan based on each input scan. For this reason, writing telescope control files based on this optimization mode is not allowed.
HAS.
For this mode, the user provides the scans that should be observed. All parameters of the scans are retained, except the times. As SCHED runs, once one scan is processed, the next is chosen from those that remain based on an attempt to come close to the desired reference station hour angle. The user can specify the desired hour angle, or can take the default which is to spread the scans on each source evenly over the time interval during which it can be observed with enough stations above a specified elevation limit. The scan is chosen based on a weight which is the sum of a weight based on deviation from the desired time, a weight based on the slew time from the previous scan (to help try to minimize time lost to slewing), and weights based on proximity to the start and end of the time the source can be observed. There is an example schedule among the sched examples called eghas.key that shows a way of using this mode for survey type observations where there is a desire to observe many sources, each over a wide hour angle range to get good UV coverage.

OPTMODE=HAS should not be used to schedule projects longer than 24 hours. In that case, hour angles can be ambiguous. Note that for normal schedules the 4 minute difference between the sidereal and solar days will not be important partly because only scan start times are considered. However there is just a chance of weird behavior for an observation of 24 hours UT duration and short scans.

There are a number of input parameters to help guide the HAS mode in it’s selection of scans. Important parameter include OPDUR, which sets the total length of the observations, OPMINANT, which sets the minimum number of stations that must be up for a scan to be chosen and OPMINEL, which sets the minimum elevation a station must be above to be considered to be up. Note that to be considered to be up, a station must also be above the local horizon as specified in the station catalog.

OPHASTA sets the reference station for this mode. This is the station at which the hour angles will be measured. Either the full name or the station code, if unique, can be used. OPHA sets the desired hour angle (at the reference station) for this scan. OPHAWID sets a normalization time interval relative to the desired hour angle over which the scan weight increases. OPHAWT is a normalization factor for weights related to time offset from the desired hour angle. This and other weight normalization factors mentioned below help adjust the relative importance of the different factors such as offset from the desired time, slew time, and proximity to other scans on the same source. OPHASTA is used to set the station for which the desired hour angles apply. OPMINSEP sets the minimum separation of scans on a source as a fraction of the spacing of scans that would be used if they were spread evenly across the available time for that source. OPSLEWTI and OPSLEWWT set the reference time and the normalization factor for the weights related to slew time. The slew weight is OPSLEWWT * ( 1 - (slew time))/OPSLEWTI). OPHLIMTI and OPHLIMWT set a similar normalization and weight for the proximity to the extreme times at which a source can be observed. This latter is used to encourage a scan on the source, for example, before it sets. OPHMAXDT sets the maximum deviation from the desired hour angle at which a scan will be considered. This prevents using very inappropriate scans when no other scans are available. Most of the above parameter can have different values for different scans.

The equations for the various weights are given in the descriptions for the parameters OPHA, OPSLEWTI, and OPHLIMTI. For the most accurate information on how weights are set, look at the code in $SCHED/src/Sched/opthas.f.

When the HAS mode is used, a lot of information from the guts of the algorithm can appear in the sched.runlog depending on the setting of the parameter OPPRTLEV. For each output scan, some details of the weights etc for each possible choice from among the input scans are given (OPPRTLEV=3) or just a summary for the scan can be given (OPPRTLEV=2 or higher). At the end, for OPPRTLEV=1 or higher, the properties (like available observing time) and fate of each input scan are given in a table. Also a number of summary parameters are given for any OPPRTLEV. All this information, while bulky, should help a user figure out how to drive the program — how to set set the related input parameters. But beware that, for OPPRTLEV=3, the sched.runlog can be very large.

While constructing a schedule using this mode, it is very useful to use the plotting capability of SCHED. The UPTIME and UV Plot capabilities are especially useful in understanding what you have. Also note that when SCHED runs, it creates an output file with the extension .sch that could be used as the scan input section for another run of SCHED. So if the optimization mode comes close, but you wish to make a small change, it is possible. This is an old but little used capability and has not actually received any maintenance for a long time as of late 2005.

In its early form, the HAS mode is meant to be useful particularly for scheduling surveys. But at the moment, there is no way to associate scans so it would be difficult to use it for phase referencing. Also it would be awkward to use to schedule blocks of scans around the sky for atmospheric solutions (for aips task DELZN). These limitations should be removed in future versions.

HIGHEL:.
This mode is used, mainly for test observations, to allow SCHED to pick a scan with good elevation across the array from among a group of scans. The number of scans from which to pick is specified with HIGROUP. SCHED will do the geometry calculations for each of the HIGROUP scans and pick the one with the highest minimum elevation. It will keep that scan and skip the others in the group. This is especially useful for the data quality tests and startup scripts. See example dqhiel.key.

In some optimizing modes, SCHED will not schedule a scan that crosses 0 hr UT. This is also used to be true for dwell time scheduling, but it no longer seems to be useful — downstream processing doesn’t trip over such scans.

Note that the optimization modes are somewhat experimental. If they are used, the output schedule should be checked carefully.

Argument: A mode.

Options: ’NONE’, ’SCANS’, ’CELLS’, ’CSUB’, and ’UPTIME’

Default: NONE

Usage: Only one used in schedule --- the last.

Example: OPTMODE ’CELLS’

OPTLOWT

OPTLOWT is a time scale in minutes for upweighting any low elevation data in optimization modes CELLS and CSUB if other low elevation cells are not being sampled. See OPTMODE for more details.

Argument: Any time in minutes (mmm.mm format)

Options: Any time

Default: 15 — this is a reasonable value.

Usage: Only one value used for project.

Example: OPTLOWT = 10

OPTSLEW

OPTSLEW is a characteristic time scale in minutes for slews beyond which to start discouraging use of scans on the grounds that the slews are too long. This is used for several optimizing modes. See the description of OPTMODE for more details.

Argument: Any time in minutes (mmm.mm format)

Options: Any time

Default: 1.0 — a reasonable value.

Usage: Only one value used for project

Example: OPTSLEW=2.0

OVERRIDE

OVERRIDE is a switch that programmers can use to allow them to bypass restrictions imposed on most users. Commonly this will be to allow them to test features that users are not yet allowed to try. It is unlikely to be useful to users, only to programmers.

OVERwrit

If OVERwrit is specified, SCHED will overwrite any output files that already exist on disk. By default, SCHED will abort if it finds any old files of the same names as those it is trying to create. That mode is provides some protection against errors, but may be annoying when running lots of test cases.

Argument: None

Options: None

Default: Do not overwrite files.

Usage: Only one specification used — the last

Example: OVERWRIT

PCAL

PCAL sets the mode of the pulse cal generators on the VLBA. The generators can be off or can generate tones every 1 MHz or every 5 MHz. The input here can be used to change the mode from scan to scan. A default can be established in the setup file. Note that, if PCAL is specified in the schedule, it will override what is in the setup file, even if a new setup is invoked.

Control over the phase cal detection is not implemented for telescopes controlled by means of the VEX file. See notes on MkIV and S2 for details. In the EVN, standard practice is to use 1 MHz spaced tones at integer MHz values. Spectral line users that want to switch phase-cal insertion off should send special instructions to individual telescopes, as well as specifying it correctly in the schedule.

Argument: The pulse cal mode.

Options: , ’off’, ’1MHz’, or ’5MHz’. A causes the setup file value to be used.

Default: Use the setup file value. If none there, use ’1MHz’.

Usage: Defaults to previous scan. This applies even if there is a change of setup.

Example: PCAL=’off’

PCENTERS

Specifying PCENTERS followed by a ”/” causes SCHED to read groups of phase centers for use with multiple-phase center processing on the DiFX correlator. This is much like the reading of in-line catalogs with SRCCAT or STACAT. Each specified group has a name specified with NAME and a list of source names specified with SOURCES. All of these sources should be in the source catalogs. It will be common to use a file, specified with SRCFILE2 to specify all the “sources” used as phase centers.

After the last phase center group, a line with ENDCENT / should be given to return SCHED to reading normal program input. There is an example egcent.key that demonstrates the capability. The main effect will be the listing of the phase centers

Argument: Just the word PCENTERS followed by a ”/”

Options: None

Default: Not used

Usage: Use only once per schedule file.

Example: PCENTERS /

PEAK and NOPEAK

PEAK, if specified, will cause commands to be issued to tell some antennas to peak up their pointing. NOPEAK causes SCHED to stop issuing those commands.

As of March 1999, PEAK is no longer used to control VLA pointing. Please see parameter VLAPEAK.

Warning, NOPEAK takes precedence over PEAK if given in the same scan. SCHED has no way to tell that the PEAK is new rather than left over from the previous scan. Often NOPEAK is given right after the peaking scan inputs to ensure that peaking doesn’t get left on in the next scan. But if that next scan is meant to be a peaking scan, say on a different set of antennas, you will not get what you want. We have received user files like this.

For the VLBA, if PEAK is greater than 0, a peakup will be done using the channel number specified by the PEAK argument. The peakup begins either when the scan starts, or when the antenna reaches the source, whichever is later. But the on-line system will wait for a maximum of 30 or 40 seconds to reach source before giving up. If it will take longer than that to reach source, a dummy scan or a gap between scans should be inserted. The peakup routine reads the total power after being on each position for 2 seconds and then goes on to the next position. The pattern contains 10 points. Therefore the peakup will take 20 seconds plus slew times which may be as little as 30 seconds - call it 45 seconds to be conservative - at high frequencies. It could take significantly longer at low frequencies but there is no good reason to use reference pointing there. After the peakup is done, the results will be used until either another peakup is done or the project code changes. Hopefully, we’ll have some way to turn it off eventually.

It will be common to peak up at a different frequency from that being used for observing (eg peak at 7mm for 3mm observations). It will also be common to peak on a line source during a continuum observation. Therefore a different setup file will be needed for the peaking scans. It is reasonable to use the standard pointing setup files. They have names like pt7mm.set. They use FORMAT=NONE which causes the on-line system on the VLBA to not touch the formatter. Note that this is very likely to mean that any pulse cal data gathered during such scans are likely to be spurious.

For stations other than the VLA and VLBA, adding a PEAK specification to a scan will help trigger reference pointing observations. This is common for the GBT and Effelsberg.

See the section on reference pointing for much more information on easy ways to insert pointing scans.

This command triggers the addition of REFERENCE_POINTING INTENTS to the VEX file. When similar intents are added using VLAPEAK, they are prepended by VLA:. When they are added because of the use of PEAK, they will not have a station identifier. The scans before the first scan in which reference pointing is requested with PEAK will have "INTENT = REFERENCE_POINTING_OFF". All scans for which PEAK is greater than zero will have "INTENT = REFERENCE_POINTING_DETERMINE". After the first determination, any scans with PEAK less than or equal to 0 will have "INTENT = REFERENCE_POINTING_APPLY". The PEAK scheme needs to be enhanced if we are going to treat different stations differently.

Argument: A digit that for the VLBA is a baseband channel number.

Options: See discussion above.

Default: Don’t peak up.

Usage: Defaults to previous scan.

Example: PEAK=3

PEAKFILE

PEAKFILE is used to specify an external file containing parameters to control automatic insertion of reference pointing scans. The default is the file provided with the SCHED distribution. The same information can be put in the main SCHED input using PEAKINIT.

Argument: A file name of up to 80 characters

Options: Any file name

Default: $SCHED/catalogs/peak.cmd on unix systems.

Usage: Only the last value specified is used.

Example: peakfile=mypeak.cmd

PEAKINIT

PEAKINIT tells SCHED that the following lines, up to a ENDPEAK are input in the same format as the PEAKFILE and as described in the section on reference pointing.

Argument: No argument.

Options: None

Default: Not set

Usage: Generally only used once.

Example: PEAKINIT /

PHONE

PHONE is the Principal Investigator’s telephone number before and after the project. See OBSPHONE for the number during the project. It is for the cover information. It must be provided for observations that record data.

Argument: Text of up to 64 characters.

Options: Any.

Default: Blank.

Usage: Only one value used, the last.

Example: PHONE=’+1-505-835-7392. (Ask for ET).’

PINAME

PINAME is the name of the Principal Investigator. Actually, the person who should be used here should be the one who is organizing the project, not necessarily the one leading the proposal. With 64 characters, more than one person could be given. SCHED will abort if PINAME is not given for observations that record data. This is for the cover information.

Argument: Text of up to 64 characters.

Options: Any.

Default: Blank, causing SCHED to abort.

Usage: Only one value used, the last.

Example: PINAME=’E.T. Smith’

PKWATCH

PKWATCH is used with the automatic insertion of reference pointing scans. If specified, information will be sent to the standard output about how pointing sources are chosen. This may help the user understand why expected sources are not used or other problems of the sort. It produces lots of output so it is best to redirect the program output to a file when it is used. In unix, this is done by running SCHED with a line of the form:

sched < eg3mmc.key > ptg.out

Argument: No argument

Options: None

Default: Not set — no special output

Usage: Only last value used.

Example: PKWATCH

PLOT

PLOT is a switch that activates the plotting section of SCHED which is described more fully in Section 1.5. If plotting is desired, it is best to start SCHED interactively and specify PLOT and SCHEDULE=yourfile.key /. SCHED will then go get the schedule from yourfile.key (substitute your actual schedule file name) and then come back for interactive input to the plot section.

Argument: None.

Options: None.

Default: No plotting.

Usage: Only one used per schedule — the last.

Example: PLOT

POINT

POINT is used to tell SCHED to convert this scan to a reference pointing scan. If the argument is zero (which is the value it will get if POINT is specified without an argument), all stations that are in any group and have appropriate frequencies as specified in the PEAKFILE (see also PEAKINIT) will be used. If POINT has a value, only stations in that group from the PEAKFILE will be used. When POINT is specified for a scan, SCHED restricts the stations to those in the pointing group(s), switches to the pointing setup file, sets DOPPLER if the source velocity (first) is not zero, turns off recording, and sets other parameters needed to make a pointing scan. The parameters of the main scan are not affected. The object is to allow the user to explicitly set the times and source for pointing, but allow SCHED to take care of all the other messy details of converting the scan to a pointing scan.

POINT=-1 means don’t add a pointing scan even if you can. This is useful especially when AUTOPEAK) has been specified, but you are doing low frequency scans.

To turn AUTOPEAK) back on after using POINT=-1, set POINT to a value less than -1, say -2 or -999 (the value it has in the program if not set).

Argument: None or a number. None means zero. The number specifies a pointing group. -1 means don’t add pointing here.

Options: Any integer 0 or above, but should match a pointing group if not zero

Default: Not set (actually set to -999)

Usage: Set back to the unset state for each scan to avoid doing the whole schedule in pointing mode

Example: POINT=2

PN3DB and NOPN3DB

PN3DB tells SCHED to write a VLBA tracking test sequence in the VLBA control file for this scan. NOPN3DB tells SCHED to stop writing such sequences. This parameter should only be of interest to VLBA operations staff. The sequence, which is not a loop, starts with a scan of length PTSLEW to set levels at the half power point, then does a 15 second scan at the same place to fix those levels, then does one scan each of length PTDUR at off source and on peak positions, then tracks the source at the azimuth half power point. That is followed by an off source, on source, and half power in elevation tracking sequence. PTINCR in the setup file is used to set the distance to the half power point. The periods of tracking are the full scan duration minus all the level fixing, off, and on scan durations, divided by two. Scan durations of about an hour are appropriate.

Argument: None.

Options: None to set. NOPN3DB to go back to non-pointing modes.

Default: Not used.

Usage: Reverts to previous scan if not specified.

Example: PN3DB

PRECDATE

The user provides SCHED with source coordinates in one of the J2000, B1950, or DATE coordinate systems. SCHED then determines the source coordinates in the other systems. The J2000 and B1950 systems are not stationary with respect to each other. To do a proper conversion, it is necessary to specify for which date to do the conversion. This date is specified using PRECDATE. When SCHED converts from, for example, B1950 to J2000 coordinates, it uses the B1950 equations to precess to PRECDATE, and then the J2000 equations to precess from there to equinox 2000. If the wrong date, by many years, is used, the errors in the conversions will be a few tenths of an arc second. This is enough to harm phasing of the VLA at high frequencies and enough to be rather undesirable for positions used on the correlator.

The correct PRECDATE to use depends on various factors. If the target source coordinates are being provided in the J2000 system, as they really should be, then it doesn’t matter much. The correlator and the VLA will be given the J2000 positions so no conversion is involved. Some antennas will be given B1950 coordinates for pointing, but for single dishes, the few tenths of an arcsecond differences that can be caused by different PRECDATEs are not important.

The more important case is when the user has a B1950 coordinate for the target source and wants SCHED to take care of the conversion to J2000. Then the correct PRECDATE should be used. The correct date depends on how the B1950 coordinates were measured. If they were determined based on absolute measurements made on some date, that is the date that should be used. However, most target source positions will be based on measurements of offsets from some calibrator. Then the date that should be used depends on the nature of the calibrator positions. E.g, MERLIN uses a PRECDATE of 1950.0 as the default in the STARLINK COCO precession routine. On MERLIN, The calibrator positions presumably are all based on measured positions originally determined in J2000 (by VLBI etc), then converted to the B1950 coordinates that are required by the on-line system. Those conversions have all been done assuming an “observe” date of 1950.0. Thus, if you have B1950 source positions determined by offsets from a calibrator using MERLIN, PRECDATE=1950.0 should be used.

If anyone knows what other systems of general interest do, let Craig Walker know and a section can be added here.

The default PRECDATE in SCHED has changed a few times over the years. Prior to 5 Aug 1997, a date of 1985.0 was hardwired into the program. After that, the user parameter was introduced with a default of 1997.0. On 6 May 1998, the default in the development version of the code, and hence the next release (unknown date at this writing) was changed to 1979.9, the old VLA value (the EVLA does not use B1950 coordinates at all).

Argument: A fractional year.

Options: Any valid time. See the discussion above.

Default: 1979.9

Usage: Only one value is used.

Example: PRECDATE = 1950.0

PREEMPT

PREEMPT is used to allow, or not, scans to be preempted for other purposes. There are two cases. PREEMPT = EXTRA tells /schedb and VLBA operations to treat the scans as extras that can be used to help fill gaps between projects that often occur with dynamic scheduling. PREEMPT = NO tells operations not to use the Pie Town and Mauna Kea antennas at the time of the scan for daily USNO Earth Orientation Parameter (EOP) observations. PREEMPT = OK means that the time of the scan can be used for the EOP observations on PT and MK.

The PREEMPT = EXTRA option should only be used for a block of scans at the beginning of the project and another at the end of the project. These scans can, and normally will, extend outside the time assigned by the Time Allocation Committee. The scans that do not have PREEMPT = EXTRA are considered to be the “core” and should stay within the time allocation. If SCHED finds any “EXTRA” scans in the “core”, it will complain and stop. The EXTRA scans should be designed to enhance the goals of the project but should not be critical to it as they may well not get observed. Also, they should not be used to do what is effectively a different project.

Scans that have PREEMPT = EXTRA will not be written to the output files other than the summary file unless they are included in the range of scans specified with DOSCANS. The files affected are the .vex, .oms, crd.xx, sch.xx, and .flag files. These include all the antenna control files, so as far as the telescopes are concerned, these scans do not exist unless explicitly included in DOSCANS. Generally DOSCANS should only be used by VLBA schedulers.

Starting in October 2011, the VLBA has been used to provide daily Earth Orientation Parameter (EOP) observations for the U.S. Naval Observatory in return for financial support for VLBA operations. These observations are a geodetic style run of duration up to 1.5 hours using the Pie Town to Mauna Kea baseline. The observations were happening within about 4 hours of 18 hours UT. In early June 2013, they were shifted to within about 4 hours of 7 UT, during the night.

These observations cause some disruption to normally scheduled projects. The fixed and dynamic projects are scheduled in the normal manner. Then, if possible, the USNO observations are inserted in gaps between other projects. If that is not possible, the USNO observations preempt the normal project for the two stations involved. An effort to minimize the impact on the normal project is made. Parameter PREEMPT allows the PI to help with that minimization by specifying portions of the project that can be preempted and portions that should be protected. For example, the parameter can be used to protect key calibration observations.

PREEMPT can be specified for each scan and has three allowed arguments — ’EXTRA’, ’NO’ and ’OK’. The default, ’OK’, means that the scan be preempted and is a “core” scan. ’NO’ means that it should be protected from preemption for the EOP observations. ’EXTRA’ means that this is an extra scan at the beginning or end. ’EXTRA’ implies ’OK’ as far as preemption for EOP observations is concerned. The parameter need only be specified when it changes.

SCHED will examine the PREEMPT specifications and identify time periods of at least 1.7 hours when all scans allow preemption. Those times are listed in the .sum file and the new .preempt file. Shorter periods that include the start and/or end of the project are also listed as those would allow a partial overlap with the USNO observations.

If there is a period of more than 4 hours between the > 1.7 hour preemptable periods, SCHED will complain. If such periods are left in the schedule, the user requests for scan protection may be ignored when choosing when to insert the USNO observations. If the whole project is less than 4 hours long and is all protected, a warning will be issued, but preemption would probably only occur if the project is adjacent to a higher priority project that also cannot be preempted.

If PREEMPT is not specified for any scans, but the project uses automatic generation of geodetic segments, the geodetic segments will have PREEMPT default to ’NO’. This helps avoid problems for legacy schedules.

Argument: A character string of up to 5 characters.

Options: ’EXTRA’, ’OK’ or ’NO’. No other strings allowed.

Default: ’OK’, except see text about geodetic segments.

Usage: Defaults to previous scan.

Example: PREEMPT = ’NO’

PRESCAN

The topic of controlling scan timing is discussed in detail in the Scan Times section.

Please note: PRESCAN is retained mainly for backwards compatibility and should not normally be used. However it may be useful for a few situations with modern schedules. For example, if the user using DWELL wishes to push the scan further away from the preceding scan, then adding a positive PRESCAN, and lengthening the DWELL time by the same amount will do the job. That is an alternative to increasing TSETTLE in the station catalog, which the user may not normally want to touch.

Originally, PRESCAN was the mechanism for introducing gaps between scans. However that function is now better handled using the separate parameters GAP, PRESTART, and MINPAUSE.

PRESCAN specifies a time by which to offset the nominal start of a scan from what has been determined based on all other criteria. It is applied after all scan timing has been settled. It won’t back up (negative value) over the stop of a previous scan, but it would be capable of messing up scan timing set by other parameters. It should only be used with considerable care as it should not be considered a carefully maintained feature.

Note that PRESCAN is treated as a UT time regardless of whether or not LST scheduling is specified (it is added to the start time after the schedule times are converted to UT internally in SCHED).

If you are writing VEX files, please see the discussion of restrictions on tape stop time given in the section on parameter GAP.

Argument: A time.

Options: Any time.

Default: Zero for all systems except legacy VLBA and MKIV DAR, for which it is 5 seconds.

Usage: Defaults to previous scan.

Example: PRESCAN=20, meaning start the scan 20 seconds late.

PRESTART

The topic of controlling scan timing is discussed in detail in the Scan Times section.

PRESTART allows the recording to be started before good data is expected. It was used to give time for earlier correlators to synchronize playback. All correlators now in use are able to sync quickly so the need to adjust start times to allow for synchronization is basically gone. In practice, the the Mark5A units take few seconds to get going on record which is why the default is 5 seconds for the legacy systems. For VLBA/RDBE and VLA/WIDAR systems, the default is zero. The following discussion is kept to describe the function of PRESTART while the parameter is available.

PRESTART gives a time by which to start the recording at a site before the nominal start time as established by START, GAP, DWELL, PRESCAN etc. Like PRESCAN, if the requested PRESTART moves the start of motion to before the stop time of the previous scan, the recording will just be kept moving. But, unlike PRESCAN, this time shift is done on a per-station basis — if a station was not participating in the previous scan, it’s recording start will be shifted the full PRESTART time, even if that means starting while other stations are still recording the previous scan. Also unlike PRESCAN, the shift due to PRESTART is not reflected in the scan times reported in the summary or sch files.

The amount of time by which the recording start is shifted before the nominal start time can be displayed using the TPSTART option in the SUMITEM list.

See the section on scan times for more information on controlling scan times.

For PCFS (VEX) controlled stations, the user should bear in mind that all start times currently (Oct. 2001) must be equal. SCHED will issue a warning if this condition is violated.

Starting the recording early allows time for the correlator to synchronize the inputs from different stations before the start of good data. Anytime the recording stops, the correlator takes time to resync. On the old hardware VLBA correlator, that time is empirically about 8, 13, and 25 seconds for speedup factors 1, 2 and 4 respectively. Therefore it was best to keep recording through short gaps. On other correlators playing Mark5 media, sync is rapid — on the order 1 second or less at the JIVE and MarkIV correlators and the DiFX software correlator (current VLBA), so these concerns are not so great.

One exception when it may be a good idea to stop recording is when there will be a formatter reconfigure. These happen when the internal switching in the formatter, or the pcal detection setup, change (number of channels, BBC assignments, sidebands, pulse cal detector frequencies etc.). The media does not receive good data while this is happening and the correlator can have problems recovering sync afterward. At least a normal resync must happen and occasionally (maybe 10-20% of the time) the correlator will get in a bad state and take a long time, maybe over a minute, to resync. If the media are stopped during a reconfigure, a resync will be done normally.

Argument: A time.

Options: Any time.

Default: 5.0 for legacy systems, 0.0 for VLBA/RDBE and VLA/WIDAR systems.

Usage: Defaults to previous scan.

Example: PRESTART=15, meaning start the recording 15 seconds early.

PTDUR

PTDUR is the duration of each scan during a pointing loop for the VLBA. This parameter should not be of concern to anyone but VLBA operations staff.

Argument: A time in seconds.

Options: Any.

Default: 20

Usage: Only one value accepted, the last.

Example: PTDUR=15

PTSLEW

PTSLEW is the time allowed in a pointing sequence to get to source before beginning the raster. This parameter should only be of interest to VLBA operations staff. In actual use, if a scan start time is specified, the interval between that start time and the previous stop time is added to the PTSLEW to set the duration of the slewing scan. For most pointing observations, it is probably best to set PTSLEW to something small, perhaps the same as PTDUR, and use dwell time scheduling.

Argument: A time in seconds.

Options: Any

Default: 160, a sensible choice.

Usage: Defaults to previous scan.

Example: PTSLEW=180

PTVLBA and NOPTVLBA

PTVLBA tells SCHED to write a VLBA pointing sequence in the VLBA control file for this scan. NOPTVLBA tells SCHED to stop writing such sequences. This parameter should only be of interest to VLBA operations staff. Note that this is not a peak in the sense that the antenna does not go to the derived position after the pattern. It is used for measuring pointing offsets and pointing equations. Parameters PTSLEW and PTDUR set, respectively, the time allowed to get to source and the time spent at each position in the pointing pattern.

Argument: None.

Options: None to set. NOPTVLBA to go back to non-pointing modes.

Default: Not used.

Usage: Reverts to previous scan if not specified.

Example: PTVLBA

QUAL

QUAL specifies a qualifier that will be written along with the source name to the VLA and VLBA schedules. It is useful for distinguishing scans of different types on the same source.

QUAL is not passed to a VEX file.

Argument: An integer of up to 3 digits.

Options: Any integer of up to 3 digits including sign.

Default: 0 but 1 for first scan of frequency switching if something else not specified. Depends on scan for pointing.

Usage: Reverts to previous scan if not specified.

Example: QUAL=34

RECord and NORECord

RECord tells SCHED to record data for this scan. Recording can be turned off by specifying NORECORD. This can be convenient for, as an example, VLA phasing scans.

NORECORD will insert scans in the VEX file, which have recorder = 0. This will lead to the desired function in some cases, namely a complete scan, but without data being recorded.

Argument: None. Actually a non-zero argument would have the same effect as specifying NORECORD

Options: None.

Default: Make the recording.

Usage: Reverts to previous scan.

Example: RECORD

REPeat

REPeat = n causes the scan to be repeated n times. If GROUP is specified with a value of m, it causes m scans, starting with this one, to be repeated n times. DURATION or DWELL should be used if REPEAT is used. REPEAT and GROUP, together, provide a simple looping capability.

Argument: An integer.

Options: Any.

Default: 1

Usage: Reset to 1 on next scan.

Example: REP=5

REVERSE

REVERSE is an obsolete parameter now that tape is no longer being used.

REVERSE requests that the direction of motion of the wide-band Mark III or VLBA tape be reversed at the start of the scan. No rewinds or fast forwards will be done if this is requested. REVERSE is not needed normally. SCHED checks each scan to see if it will fit in the current direction. If not, the tape will be reversed before the next scan begins. If REVERSE is specified with no argument, the tape will be reversed at all stations. If one or more station names are given, the tapes will be reversed at only those stations. Station codes may be used instead of station names.

Argument: None or a list of stations.

Options: No argument or the name of any stations in the scan. Not case sensitive.

Default: No reverse.

Usage: Reverts to no reverse on next scan.

Example: REVERSE or REVERSE=VLBA_KP,VLBA_LA

REWIND

REWIND is an obsolete parameter now that tape is no longer being used.

REWIND requests that the wide-band Mark III or VLBA tape be rewound before the scan starts and during the prescan. If REWIND is specified with no argument, the tape will be rewound at all stations. If one or more station names are given, the tapes will be rewound at only those stations. Station codes may be used instead of station names.

Argument: None or a list of station names.

Options: No argument or the names of any stations in the scan.

Default: No rewind, unless there is insufficient room left during a backward pass to fit the next scan or a tape change is requested.

Usage: Reset to no rewind for next scan.

Example: REWIND or REWIND=’vlba_fd’

ROTATION

ROTATION is used in VLBA test observations to specify an increment to the subreflector rotation value used for the subreflector position. This is added to the nominal position known by the on-line system for the particular receiver.

Note that changing the rotation also changes the pointing offset in a frequency dependent manner.

Argument: A rotation angle in degrees.

Options: Any rotation angle

Default: 0.0

Usage: Default to previous scan.

Example: ROTATION = 10

ROTPAT

ROTPAT causes SCHED to expand pointing patterns to include a raster in focus and rotation. The position offsets in this raster are specified by FOCOFF and ROTOFF. ROTPAT is only expected to be used by VLBA testers.

ROTPAT have a value which is the number of positions in focus/rotation in the pattern. It can only be used for 13cm, 6cm, 4cm, 2cm, 1cm, 7mm, and 3mm. Note that the overall scan must be ptslew plus rotpat times ( 2 times ptdur plus N times 10 times ptdur ) long to fit a full pattern with N pointing loops at each focus/rotation position.

A typical set of offsets would be ROTOFF=-1.5, 0, 0, 0, 1.5 and FOCOFF=0, -1, 0, 1, 0 with FOCPAT=5.

Argument: A number of focus/rotation positions. Up to 20.

Options: Any number up to 20.

Default: 0 - Only do the central focus/rotation position.

Usage: Only one used for the experiment

Example: ROTPAT=5

ROTOFF

ROTOFF gives the offsets in subreflector rotation for a focus/rotation raster. See ROTPAT for details.

The values are offsets to be multiplied by the nominal offset for the band as understood by the program.

Argument: Up to 20 real numbers - the number of nominal recrements in rotation for each position of a focus/rotation raster.

Options: Any number. 1.0 or 1.5 typically.

Default: 0.0

Usage: Only one set used per experiment.

Example: ROTOFF=-1.5,0,0,0,1.5

SCANTAG

SCANTAG allows the user to specify a name for the scan. That name appears in the summary file under the scan number. Note that it resets after each scan. This is just to help users with bookkeeping when constructing complicated schedules with loops and other constructs that complicate knowing which output scan is which scan in the summary. The name is limited to 4 characters to fit in the desired column in the summary file.

Argument: Any character string of up to 4 characters.

Options: Any character string.

Default: Blank

Usage: Reset after each scan, although all instances of that scan in a loop will share the name.

Example: SCANTAG=’Cal2’

SCHedule

SCHedule allows SCHED to be started interactively to specify options that might vary from run to run (such as PLOT, DEBUG etc.) and still get most of it’s input from an external file. That external file is specified with SCHedule.

Under unix, environment variables may be used. For example, if SCHED is defined to mean /users/cwalker/sched, the base area under which all sched stuff is kept (substitute your local directory), then one can specify one of the example schedules with SCHEDULE = $SCHED/examples/manual_1.key. Use the setenv (c or t shell) or export (korn shell) to set environment variables.

Argument: A file name of up to 80 characters.

Options: Any valid file name.

Default: Use interactive input.

Usage: Only one used. It will apply to all following input.

Example: SCH=/users/cwalker/bw12.key

SETINIT

Setup file information can be specified in the main input file. If SETINIT is specified, the next groups (to ENDSET), are assumed to be setup file information. The setup name will be the argument to SETINIT. Multiple setup files can be specified this way. An argument must be specified or the setup information will not be read.

If SETINIT is found, the end of the input group (everything up to the “/”) is not considered the end of inputs for this file. The next inputs after the setup data are entered will continue to apply to the current file (usually the first).

Since SETUP can specify a file name, when there isn’t an embedded setup file, it must be case sensitive. As a result, the case of the argument of SETINIT much match SETUP.

Argument: A setup file name of up to 80 characters. Case sensitive.

Options: Any character string. Must not be blank.

Default: Will not assume that setup information will follow.

Usage: Will revert to assuming no setup information will follow.

Example: SETINIT=BW008.6CM.SET

SETUP

The argument to SETUP is a file name where setup information can be found. A setup file must be specified. See Section 3.6 for details of what should be in the setup files. A new setup file can be specified for each scan for mode switching. The SETUP file name may refer to an external file that can be read by SCHED or it may refer to a setup imbedded in the main SCHED input following a SETINIT command, whose argument is the setup file name.

Under unix, environment variables may be used. For example, if SCHED is defined to mean /users/cwalker/sched, the base area under which all sched stuff is kept (substitute your local directory), then one can specify the setup file with SETUP = $SCHED/setups/v6cm-128-4-2.set. Use the setenv (c or t shell) or export (korn shell) to set environment variables.

Since SETUP can be a file name and some operating systems (unix, Linux) are case sensitive, SETUP must be treated as case sensitive, including when referring to an embedded setup (from SETINIT).

Argument: A file name of up to 80 characters. Case sensitive.

Options: A valid file name.

Default: No setup file used.

Usage: Defaults to previous scan.

Example: SETUP=’/users/cwalker/sched/v6cm-128-4-2.set’

SOURCE

SOURCE is used to specify the source name. It is required for the first scan and whenever there is a change. The name must match, in a case-insensitive sense, one of the names of a source in the source catalogs (recall that 5 different names or aliases are allowed for each source).

SOURCE may be the name of a Solar System object. If so, if an EPHFILE: has been specified, and if the object is not in the source catalog, SCHED will determine the position and planetary motion of the object using a JPL ephemeris. This position is very good — certainly good enough for use for pointing which is the primary use envisioned (note that much work would be required on the correlator to correlate planetary observations). There is a similar capability for pointing at satellites using orbital elements in SATFILE or TLEFILE that are specified in the SATINIT section.

The Solar System objects that SCHED understands are Mercury, Venus, Moon, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, and Sun. Topocentric positions and rates will be provided for VLBA antennas if one of these is specified. Note that SCHED does not understand how to specify moving objects to antennas that don’t use the VLA or VLBA control file types. Specifically, solar system sources are not currently supported for VEX output files.

Argument: Text of up to 12 characters.

Options: Any source in the catalogs.

Default: None.

Usage: Defaults to previous scan.

Example: SOURCE=’3C120’

SRCCAT

SRCCAT is a flag to indicate that the following inputs are to be treated as an in-line source catalog. See Section 3.2 for details of source catalog contents. The catalog input is terminated by ENDCAT / to resume schedule input. It is best to specify SRCCAT / as a separate line not part of other SCHED keyin input. SCHED stores the source catalog information in internal arrays which have a maximum size that may depend on the computer but is 500 in the distributed version. All sources found in in-line catalogs are stored in these arrays because they may be read before all scheduled sources are known. In contrast, when an external source catalog is read, only scheduled sources are kept. See the examples in Section B.3 for illustrations of how in-line source catalogs are used.

If SRCCAT is found, the end of the input group (everything up to the “/”) is not considered the end of inputs for this file. The next inputs after the source data are entered will continue to apply to the current file (usually the first).

Argument: None.

Options: None.

Default: Not used.

Usage: There can be as many in-line catalogs as desired, consistent with the maximum number of allowed sources in the in-line catalogs.

Example: SRCCAT /

SRCFILE

SRCFILE is used to specify the name of the external source file. See Section 3.2 for the required formats. The default SRCFILE is $SCHED/catalogs/sources.gsfc, although $SCHED/catalogs/sources.petrov is a good alternative. Assuming the environment variable $SCHED is set (see below), this is the usual SCHED source file. If SRCFILE=’none’ is specified then no external catalog will be read. The file name is simply passed to the operating system so all the usual behavior you expect normally apply, such as the use of the current directory if a path is not given.

Under unix, environment variables may be used. For example, if SCHED is defined to mean /users/cwalker/sched, the base area under which all SCHED stuff is kept (substitute your local directory), then one can specify the source file with SRCFILE = $SCHED/catalogs/sources.petrov. Use the setenv (c or t shell) or export (korn shell) to set environment variables.

There is an option to use a second source catalog file using SRCFILE2. This could be useful if one wishes to get calibrator information from the SCHED standard catalog, but also have a catalog of program sources. It is also useful when using the ability to specify many phase centers per pointing center.

SCHED will use the data for a source from the first catalog it reads that includes that source. It reads the in-line catalog first, then SRCFILE and then SRCFILE2.

Argument: A file name of up to 80 characters.

Options: Any file name or none.

Default: ’$SCHED/catalogs/sources.gsfc’

Usage: Use only once.

Example: SRCFILE=/users/cwalker/sched/sources.dat

SRCFILE2

SRCFILE2 is a second source file, treated identically to SRCFILE. This allows one to supplement the main SCHED catalog with a local, but still not embedded, catalog. It is likely to be especially useful for observations wanting multiple phase centers in each pointing center.

SCHED will use the data for a source from the first catalog it reads that includes that source. It reads the in-line catalog first, then SRCFILE and then SRCFILE2.

Argument: A file name of up to 80 characters.

Options: Any file name or none.

Default: Not used

Usage: Use only once.

Example: SRCFILE2=’centers.dat’

STACAT

STACAT is a flag to indicate that the following entries are part of the stations catalog. See Section 3.3 for details of the format. In-line catalogs can occur more than once in the SCHED keyin file. The station catalog input is terminated with a separate entry containing ENDCAT /.

If STACAT is found, the end of the input group (everything up to the “/”) is not considered the end of inputs for this file. The next inputs after the station data are entered will continue to apply to the current file (usually the first).

Argument: None.

Options: None.

Default: Not used.

Usage: Can occur as often as desired.

Example: STACAT /

STAFILE

STAFILE is the name of the external stations file. See Section 3.3 for the required formats. If STAFILE is not specified, it defaults to $SCHED/catalogs/stations_RDBE.dat. If STAFILE=’none’ is specified then no external catalog will be read.

This must be specified among the first scan inputs since SCHED will read the station catalog while setting up the first scan. If STAFILE is not specified with the first scan’s inputs, SCHED will read the default catalog. This is done because, while reading the scans, SCHED needs to know some station information (like codes in case you choose to specify them for the STATIONS input).

Under unix, environment variables may be used. For example, if SCHED is defined to mean /users/cwalker/sched, the base area under which all sched stuff is kept (substitute your local directory), then one can specify the station file with STAFILE = $SCHED/catalogs/stations_RDBE.dat. Use the setenv (c or t shell) or export (korn shell) to set environment variables.

Argument: A file name of up to 80 characters.

Options: Any valid file name or none.

Default: $SCHED/catalogs/stations_RDBE.dat

Usage: Only specify once.

Example: STAFILE=’/users/cwalker/sched/stations.dat’

START

The topic of controlling scan timing is discussed in detail in the Scan Times section.

START is used to specify the start time of the scan in UT. If LST was specified, START is assumed to be in local sidereal time. START must be specified for the first scan. For later scans, it will default to the stop time of the previous scan if not specified. Note that the start time will be adjusted by PRESCAN to the time that the recording starts.

Argument: A time in hh:mm:ss format.

Options: Any time.

Default: No default - SCHED will stop if first START is not given.

Usage: Defaults to stop time of previous time.

Example: START=13:15:00

STATions

STATions is used to specify the list of stations to be included in this scan. If there is any change to the list, the whole list must be given again. The station names given must match ones available in the station catalogs. The scans for any specific station must be in time order. Note that STATN is no longer an acceptable alternative.

The maximum number of stations that SCHED will handle is set in a parameter statement in an include file and can be varied according to the capabilities of the computer in use. At the time this was written, it was 22, but that may change.

You may specify the station code for any or all stations instead of the name. Sched will determine the station name from the catalog information and use it for the rest of scheduling. This use of station codes is only offered for STATions, FASTFOR, REWIND, TAPE, and REVERSE. All other inputs requiring station names must use the names as given in the station catalog.

Argument: A list of station names of up to 8 characters each.

Options: Any stations in the station catalog.

Default: At least one must be given for first scan.

Usage: Defaults to previous scan.

Example: STATION=EB_VLBA,GB_VLBA,VLBA_NL,VLA27,VLBA_MK

STOP

The topic of controlling scan timing is discussed in detail in the Scan Times section.

STOP is used to specify the stop time of the scan in UT. If LST is specified, the time is in local sidereal time. Either a STOP time, a DURation, or a DWELL must be given for each scan, although the DURation or DWELL can default to a previous value. If STOP and one of the others are both given then the implied stop times are compared, and if those times differ by more than 10 seconds, a complaint is generated. A simple check of a long schedule made in durations is to include the stop time for the last scan; if the schedule has problems, there will be an error message.

Argument: A time in hh:mm:ss format.

Options: Any time.

Default: Start time plus duration.

Usage: Either DURation, DWELL, or STOP is required for each scan. DURation or DWELL will default to previous scan.

Example: STOP=13:45:00

SUMITEM

SUMITEM is used to control the items listed in the summary file for each antenna. Two items are listed for each scan for each antenna on each summary pass. Up to 10 items can be requested causing up to 5 summaries to be produced in the .sum file. The items that can be requested are:

EL1:
The elevation at the start of the scan. For scans where the source is below the hardware limits or the horizon, a letter code will be included.
EL2:
The elevation at the end of the scan. The limit code will be included.
ELA:
The average elevation of the scan ((EL1+EL2)/2). The limit code will be included.
AZ1:
The azimuth at the start of the scan. The limit code will be included.
AZ2:
The azimuth at the end of the scan. The limit code will be included.
AZA:
The average azimuth of the scan ((AZ1+AZ2)/2). The limit code will be included.
PA1:
The paralactic angle at the start of the scan.
PA2:
The paralactic angle at the end of the scan.
HA1:
The hour angle at the start of the scan.
HA2:
The hour angle at the end of the scan.
EARLY:
The number of seconds that the antenna arrived on source before the scan started. Negative numbers are common and are the number of seconds that the antenna arrived on source after the scan started.
DWELL:
The number of seconds of on-source time in the scan. This does not take into account correlator resync times. See SYNC for that information. The total integration time should be the smaller of DWELL and SYNC. Note that neither takes into account the time needed to switch between receiver bands (that’s on the wish list).
SLEW:
The slew time in seconds from the previous source.
TAPE1:
The tape drive in use, the recording direction, and the head index position. Cannot be used if NOSETUP is specified. If the station only has disk, the total GBytes recorded at the station up the the end of the scan is given.
TAPE2:
The set of heads in use (for example which of the TRACKn inputs is in use) and the tape footage in thousands. Cannot be used if NOSETUP is specified.
DISK:
The total GBytes recorded at the station up the the end of the scan is given. Nothing useful is given for tape only stations. Cannot be used if NOSETUP is specified.
TPSTART:
Show the offset of the recording start time from the scan start time. This is established by parameters PRESTART and MINPAUSE
SYNC:
The expected integration time with the correlator synchronized. This takes into account time lost to resyncs and formatter reconfigures. It does not take into account slew times, which DWELL does.

If any other items are desired, please inform Craig Walker.

Users of EVN antennas (and any others controlled by the PCFS and VEX) are advised to study the listing created by EARLY. Currently there is no complete mechanism for PCFS to monitor whether the telescope was on source when the recording starts. Data taken during this time are invalid, but are not flagged automatically. Therefore it is advisable to make schedules with DWELL or inspect the listing for telescopes that arrive late on source.

Argument: Up to 10 character strings.

Options: See the description above for valid parameters.

Default: ELA, DWELL

Usage: Only one value used, the last.

Example: sumitem=el1, az1

TANT1 and TANT2

TANT1 requests that SCHED turn on antenna temperature measurement at stations in the TANTSTA1 list, if it knows how to do so for those antennas. TANT2 does the same thing for stations in the TANTSTA2 list.

This command currently has no effect on VEX, VLA, or VLBA output. In fact, as more antennas have gone to the above file types, the usefulness of this capability had been significantly reduced. As of mid 1997, the only station for which automatic Tant requests can be made is Green Bank. Be warned that such measurements take a minute or so.

Argument: None or a non-zero value.

Options: None or 0 to turn on Ta measurements. Specify a non-zero value to turn off Ta measurements.

Default: Make the Ta measurements.

Usage: Defaults to previous scan.

Example: TANT1=-1 TANT2

TANTSTA1 and TANTSTA2

TANTSTA1 is used to specify a list of stations for which TANT1 will turn on and off Ta measurements. These stations must have Green Bank or snap type files, or SCHED will abort. TANTSTA2 specifies the stations whose antenna measurements are controlled by TANT2.

As noted in the discussion of TANT1, the only station that retains the capability for SCHED to request Tant measurements is Green Bank.

Argument: A list of station names of up to 8 characters each. Should match names of stations used in the schedule.

Options: Any station names. Unrecognized names will be ignored.

Default: Any stations in the schedule that have NRAO or SNAP control file types.

Usage: Only one list, the last given.

Example: TANTSTA1=’BONN’,’JODRELL’ tantsta2=nrao

TAPE

TAPE is an obsolete parameter now that tape is no longer in use.

TAPE requests that SCHED force a tape change at the start of the scan. This will override any automatic tape changing that is going on and will reset the reference time for any following automatic tape changes. If no argument is given, the tape will be changed at all stations. If a list of stations is given, the tapes will only be changed at those stations; if a station is given that is not in the scan, an error message will be generated and SCHED will abort. Station codes my be used in place of station names.

For stations that only have one tape drive (all except the VLBA and VLA), be sure to allow enough idle time to complete the tape change. This usually means 15 minutes and SCHED will issue warnings if it is less than this. Some stations claim to be able to do it in 10. If postpasses are required, and they are currently (Feb 1997) being done at thin tape stations, an additional up to 33 minutes is required. The station operators can override the postpass to save time, at the risk of damaging tapes which cost over $(US)1000 each. An alternative is to schedule the last pass at such stations without stopping the tape. If SCHED detects that this has been done, it will issue an UNLOAD command instead of POSTPASS. Note that the automatic postpass will only be requested at sites using VLBA control files. The VEX format does not (yet) include this concept.

Argument: None or a list of up to 30 station names.

Options: No argument or a list of any stations in the scan. Not case sensitive.

Default: Not used. Automatic tape changes by default.

Usage: Must specify whenever needed.

Example: TAPE or TAPE=VLBA_MK,VLBA_NL

TAPEFILE

TAPEFILE gives the name for the tape initialization file. See Section 3.4 for content details. The alternative is to have the tape initialization details imbedded in the SCHED input following TAPEINI or to use the defaults which are fine for the VLBA.

Note that a tape initialization file is almost certainly NOT needed. Most parameters in it relate to initial tape head and pass positions which no longer make sense in the disk era. The one possibly useful parameter is the media specification, but that should be defined in the station catalog and would only be used during periods of transition.

Under unix, environment variables may be used.

Argument: A file name of up to 80 characters.

Options: Any file name.

Default: ’NONE’, causing defaults or parameters specified after TAPEINI to be used.

Usage: Only one accepted, the last.

Example: TAPEFILE=’vlba.head’

TAPEINI

TAPEINI is a flag to inform SCHED that the next group of input parameters will be tape initialization information, equivalent to one line from the TAPEFILE. See Section 3.4 for content details. Once the tape initialization parameters have been read, SCHED will return to reading the inputs for the current scan, usually the first.

Note that a tape initialization file is almost certainly NOT needed. Most parameters in it relate to initial tape head and pass positions which no longer make sense in the disk era. The one possibly useful parameter is the media specification, but that should be defined in the station catalog and would only be used during periods of transition.

Argument: None.

Options: None.

Default: Not used.

Usage: Should not be used more than once.

Example: TAPEINI /

TAPESYNC

TAPESYNC is an obsolete parameter left over from the tape era.

TAPESYNC requests that SCHED try to synchronize tape changes at the stations. This is advisable to avoid slightly staggered tape changes that would naturally result from a subarrayed schedule. Such staggered tape changes can result in lost data because there is a minimum of about 3 minutes per correlator job and a new job is needed when a station changes tape. This is a temporary restriction but was in effect in late 1996.

WARNING: TAPESYNC could cause very strange behavior if used with a schedule in which some stations are being scheduled separately from others. It should only be used when the scans as specified to SCHED are in roughly time order (for subarrays, there can be small deviations from time order and that will be ok). It is only recommended for use in conjunction with the optimization options. For any schedules in which every scan is specified in the input, it would be best to use TAPE to force the tape changes at reasonable times, if necessary.

Also, be sure that any automatically generated tape change requests occur at times with sufficient gaps at single tape stations (all except the VLBA and VLA). See the discussion of TAPE for details.

Note that, with automatic tape allocation, SCHED does not set the tape change times so TAPESYNC will have no effect.

Argument: None.

Options: None.

Default: Not used.

Usage: Last value used.

Example: TAPESYNC /

TAVLBA and NOTAVLBA

TAVLBA tells SCHED to write a VLBA antenna-temperature measuring sequence in the VLBA control file for this scan. NOTAVLBA tells SCHED not to write such a sequence. Parameters PTSLEW and PTDUR are used as they are for PTVLBA. If antenna temperature measurements are desired as part of a VLBI project, a separate scan with TAVLBA set should be requested before or after the main VLBI scan. Do not rely on a long PTSLEW to get the VLBI data since during the setup part of the scan, the requested pointing position is at a half power point.

Use of TAVLBA is not the recommended calibration method for the VLBA. The apriori gains should be used instead. The VLBA antennas are not set up for accurate single dish measurements. The a priori values were obtained during good weather when this is not so much of a problem. If the weather is good for the VLBI project, the a priori values will be good to a few percent, probably better than any Ta measurement. If the weather is poor, the Ta measurements will probably be nearly useless.

This has no effect on VEX files.

Argument: None.

Options: None set. NOTAVLBA to go back to non-pointing modes.

Default: Not used.

Usage: Reverts to previous scan if not specified.

Example: TAVLBA

TELEX

TELEX is the Principal Investigator’s TELEX number for the cover information. This parameter is still provided only for backward compatibility. Don’t bother with it. Are telexes still in use?

Argument: Text of up to 64 characters.

Options: Any.

Default: Blank.

Usage: Only one value used, the last.

Example: TELEX=’+1-910-988-1710’

TPREF

TPREF is obsolete for the vast majority of users because Mark II systems were abandoned long ago.

TPREF is the reference time for Mark II tape changes. When automatic tape changes are specified, as is done by default, they will occur at times that are an integral number of tapelengths (default 4 hours) before or after this time. Since the only really valid Mark II tape length of 4 hours divides a 24-hour day evenly, no provision is provided to specify a day.

Argument: A time.

Options: Any valid time between 0 and 24 hours.

Default: Not used; rather start time of earliest scan of the schedule is used.

Usage: Only one value accepted.

Example: TPREF=5:0:0

TSYS and NOTSYS

This is an obsolete parameter because it only affected the Green Bank control files and the SNAP file, neither of which is now in use. Note that the GBT now does continuous system temperatures in the same manner as the VLBA.

By default, SCHED requests that system temperatures be measured every scan in the NRAO (Green Bank) and snap control file types. The VLBA measures Tsys continuously so no such request is needed. For Green Bank, the system temperatures are measured at the start of every scan (as part of the “MARKIII” procedure). They are no longer measured at the end of a scan. For stations using snap files, there is no concept of “go to source, then do something”, so Tsys requests are only made at the end of each scan. NOTSYS turns off the Tsys requests (For Green Bank, it also turns off all other actions included in the “MARKIII” procedure which might include antenna temperature measurements and peaking up pointing). The Tsys measurements take a bit of time so it may be desirable to turn them off when switching rapidly between sources; however, by doing so, calibration may be compromised. The measurement of system temperatures can be turned back on with TSYS.

This has no effect on VEX files; system temperatures are measured by PCFS controlled at the beginning of every scan. Note that with thin tapes and fan-out, the time between measurements could be as long as 44 minutes. SCHED will warn if there is more than 30 minutes between Tsys measurements for PCFS systems, except on a last reverse scan which may be forced to be long in order to avoid post-passing.

Argument: None.

Options: Use it or not.

Default: Ask for system temperature measurements.

Usage: Defaults to previous scan.

Example: NOTSYS

UVMFS

UVMFS affects UV plots, allowing the user to show the effect of using multi-frequency synthesis. The first argument is the number of tracks to plot per baseline. The default is to plot one with UV in km. The second argument is the ratio of the highest to the lowest MFS frequency. The UV values will be in km the middle of the frequency range.

This option could have been implemented by paying attention to the frequencies in the setup file, and that option should be added some day. But that requires either fully specified setup files, or freq.dat entries for all stations. When SCHED is being used for configuration studies, this is an undue burden.

Note that this is also used for the UV coverage based quality measures used for configuration studies.

Argument: Two numbers.

Options: The first number is converted to an integer. The second is a real and should be between 1.0 and about 2.0, although it is unrestricted

Default: 1 and 1.0 — meaning only plot one track per baseline.

Usage: One value used for schedule

Example: UVMFS = 5, 1.3

VERSION

VERSION Version number of the schedule for the cover information. Usually this will be 1 for the first, 2 for the second, etc. Often stations get a schedule, then the PI changes his/her mind about something, or finds and error, and so creates a new version. Later at the station, it is not always obvious which is the latest version. This version number is meant to make it obvious. SCHED will abort if VERSION is not specified.

Argument: Any real number, with decimals is desired as it will be printed in F10.2 format.

Options: Any but integers are typical.

Default: 0 which causes SCHED to abort.

Usage: Only one value used, the last.

Example: VERSION=1

VEXTEST

VEXTEST is a switch that allows testing of VEX related features that have not been released for public use. It is likely to only be of interest to the SCHED developers, although it is possible that early users of new features may need it.

Argument: No argument - this is a logical

Options: No arguments

Default: Not set, which may block some VEX features.

Usage: Only last value specified will be used

Example: VEXTEST

VLABAND and VLABW

These are obsolete parameters that specified the VLA observing mode and the VLA backend filter width. They should now be specified in the setup file. Any values specified in the main input will be ignored.

VLAINTEG

Obsolete for current VLA.

VLAINTEG is used to set non-standard integration times in VLA schedules. This would be useful mainly to influence the speed with which the system phases up. The argument is in seconds. The default is 10 seconds. SCHED generates //DS cards for all scans after a VLAINTEG is specified.

Argument: Integer between 0 and 999.

Options: See list above.

Default: 10 seconds.

Usage: Defaults to previous scan.

Example: VLAINTEG=3

VLAMODE

VLAMODE is used to control phasing up of the VLA. The control can also be done directly by specifying the phasing related INTENTs, but that can be more cumbersome, especially if other INTENTs are changing from scan to scan. A phasing mode is required. For a schedule using the VLA, if SCHED does not get a VLAMODE or a phasing related INTENT, it will quit. When VLAMODE is used, SCHED will generate the appropriate INTENTs for the VEX file for the VLAMODE that is given.

VLA reference pointing and array phasing must not be requested in the same scan.

The valid VLAMODE values are:

- Do not apply or determine phases. This generates INTENT = VLA:AUTOPHASE_OFF.
’VA’ - auto phasing on all IFs. This generates INTENT = VLA:AUTOPHASE_DETERMINE.
’VX’ - Apply phasing determined in previous VA scan.) This generates INTENT = VLA:AUTOPHASE_APPLY.
’VS’ - single antenna VLBI (not available on EVLA as of 2014). May want this to keep the phase center at the antenna if at all possible. This could generate INTENT = VLA:SINGLE_DISH.

Argument: Text of 2 characters.

Options: See list above.

Default: None - required for VLA.

Usage: Defaults to previous scan.

Example: VLAMODE=’VX’

VLAPEAK

VLAPEAK is used to control reference pointing on the VLA. The user will need to provide a scan of at least 2.5 minutes on a calibrator on which the pointing can be done. The observations should be at X band. These scans can be inserted explicitly, or AUTOPEAK can be used to insert them automatically (maybe not yet). SCHED will create appropriate INTENTs for the VLA scans based on the value of VLAPEAK. It is not recommended that the user attempt to specify the pointing related INTENTs explicitly although that is not prevented. If that is done, there can be interactions with the defaulting when other, unrelated INTENTs are used.

The four settings for VLAPEAK situations of interest are:

’DETERMINE’ indicates that the reference pointing corrections should be determined starting from no offsets. This sets INTENT = VLA:REFERENCE_POINTING_DETERMINE
’APPLY’ indicates that the most recently determined reference pointing offsets should be applied. This sets INTENT = VLA:REFERENCE_POINTING_APPLY
’ADJUST’ indicates that reference pointing corrections should be determined starting with the previously determined values. The results that can be applied to later scans are the sum of the previous and the newly determined values. This sets INTENT = VLA:REFERENCE_POINTING_ADJUST
’OFF’ indicates that no reference pointing offsets should be applied and that no attempt should be made to determine them. This is the default and is what will be used at all but the highest frequencies. This sets INTENT = VLA:REFERENCE_POINTING_OFF

A pointing pattern can be done if in a scan if there are at least 150 on source. Only one pattern is done, so adding significantly more time is not useful (unlike the old VLA system).

Reference pointing is important for observations at 1cm (K band) and higher frequencies (ie Q band). It might be useful at the high end of the 2cm (Ku band) range. For more information about reference pointing on the VLA please see the Guide to Observing with the VLA section on High Frequency Observing Strategy. The pointing should be done at C or X band, with X band recommended.

VLA reference pointing and array phasing must not be attempted in the same scan. SCHED will abort if that is tried.

Argument: Text of up to 9 characters.

Options: See list above.

Default: ’OFF’.

Usage: Defaults to previous scan.

Example: VLAPEAK=’APPLY’

VLAPTIME

On the VLA, a SCHED scan intended for array phasing is broken into subscans for purposes of obtaining phasing solutions at one solution per subscan. At least 4 subscans are required to obtain reliable phases. The length of the subscans can be set separately for each scan using VLAPTIME whose argument is in integer seconds. The default of 10 seconds will be good in most cases. Longer times can be used if a weak calibrator must be used or perhaps when phasing while recording on the VLBI target source. The subscan length is passed to the VLA through the VEX file in an INTENT that is created by SCHED.

Argument: A time in integer seconds.

Options: Any time over 10 seconds.

Default: 10 seconds

Usage: Defaults to previous scan’s value.

Example: VLAPTIME=20

VLATSYS and VLANTSYS

Obsolete for current VLA.

The VLA on-line system normally applies a Tsys-based amplitude correction to data from the VLA correlator. In order to calibrate 3-antenna and phased VLA data taken with the VLA as a VLBI station, it is necessary to have raw correlation coefficients. If the Tsys correction is made, the raw correlation coefficients are lost. The old DEC10 scheme for obtaining the VLBI calibration data was based on the standard VLA correlator output as archived, so it was necessary to request that the Tsys correction be turned off. The new scheme for obtaining the VLBI calibration information involves extraction of the correlation coefficients by the on-line system before the Tsys corrections are made. Therefore it is no longer necessary to turn the corrections off and leaving them on makes it easier to use the VLA correlator data to make VLA images. The default action of SCHED is now to leave the corrections on and that should be correct for essentially all observations. However, VLATSYS and VLANTSYS can be used to turn the corrections on and off, respectively, on a scan basis just in case someone still wants to do so.

Argument: None

Options: No value (a non-zero value turns has the effect of the opposite parameter)

Default: Keep Tsys corrections on.

Usage: Defaults to previous value.

Example: VLANTSYS or VLATSYS

VLAPSRC

This parameter was developed originally for the old VLA system. It has not yet been converted for use with the VLA. But that is on the to-do list.

VLAPSRC can be used to specify the source to use for phasing the VLA. If the scan is mode VX and VLAPSRC differs from SOURCE, then a scan will be inserted in the VLA observe file in VLAPSRC with mode VA. The VLBI control file will not be affected. The stop time of the phasing scan will be 1 minute before the start of the VLBI scan or 3 minutes after the stop of the previous VLBI scan, whichever is later. If less than 2 minutes of the VLBI scan remain as a result, a complaint will be generated. It is wise to take the VLA observe file into the NRAO VLA OBSERVE program to check the slew and dwell times, since the default timing used for VLAPSRC will not always be reasonable and the phasing scan stop time may need to be adjusted. Note that, since SCHED does not generate a phasing scan for a mode VA scan or when VLAPSRC equals SOURCE, VLAPSRC need not be specified or changed for such scans; this may minimize the number of times VLAPSRC needs to be specified.

Argument: Any source name of up to 8 characters.

Options: Any source in the catalogs. ’ ’ resets to use SOURCE and turns off the special phasing scan.

Default: Uses SOURCE, which causes no phasing scan to be written.

Usage: Defaults to previous scan.

Example: VLAPSRC=’0255+164’

VLARFANT

Obsolete for current VLA.

VLARFANT can be used to specify the reference antenna for the VLA. This will be the antenna used as the source of data in single dish VLBI. For the phased array, it will be the reference antenna for the calibration solution for phasing. Note that, in phased array mode, the phase center is always at the normal VLA phase center. In single dish mode, if there are multiple antennas available to the VLA correlator, they will be correlated with the phase center at the reference antenna. This is needed so for the old VLA system so that the fringe rotators do not affect the single dish VLBI data.

Normally the reference antenna is number 10, which is the default. If that needs to change, it is unlikely that users will be aware of that fact in time to change their schedule, so either SCHED needs to be rerun by operations with the new value, or the observe deck needs to be edited. Users in the vast majority should not worry about this parameter.

Argument: An integer between 1 and 28

Options: Any intger, specifying an antenna, between 1 and 28

Default: 10

Usage: Use only once.

Example: VLARFANT=15

VLATYPE

Obsolete for current VLA.

VLATYPE specifies the type of the observation for the VLA observe file.

Argument: Text of up to 9 characters.

Options: ’VLBI’ - VLBI observation. ’CONTINUUM’ - normal VLA continuum observation. ’LINE’ - VLA spectral line observation.

Default: ’VLBI’

Usage: Use only once.

Example: VLATYPE=’CONTINUUM’

VLAUSERN

Obsolete for current VLA.

VLAUSERN is the VLA user number. Provide the PI’s VLA number (same as the Socorro AIPS number) if desired. For VLBI runs the default of 600 is fine.

Argument: Integer.

Options: Any VLA user number.

Default: 600

Usage: Only last value entered is used.

Example: VLAUSERN=332

WRAP24

WRAP24 is a switch to aid VLBA operations in dynamic scheduling of 24 hour projects. For such projects, it is useful to be able to start at a time of day different from what the user specified. This is facilitated by the parameters WRAP24 and DOSCANS. Specifying WRAP24 with no argument causes SCHED to duplicate the schedule on a second day to form a 48 hour schedule. Actually it would duplicate any schedule, but it is mainly useful for 24 hour schedules. The full 2 day (or whatever) schedule shows up in the summary .sum file. Then DOSCANS can be used to select the desired 24 hours (or whatever time).

Note that this command has nothing to do with cable wraps. SCHED does not yet have control over cable wraps — it only tries to predict them.

Argument: No argument

Options: No argument - actually anything but -9999 will have the same effect

Default: Do not wrap

Usage: Will take one specification for the observation

Example: WRAP24

YEAR

YEAR specifies the year of the stop time of the scan. This must be specified for the first scan. It is possible to specify it more often, but that will almost never be necessary.

Note that two digit years will work for years between 1950 and 2050, but are not recommended.

Also, SCHED will complain about an unreasonable year if it is not between 1900 and 2100.

Argument: Integer.

Options: Any valid year.

Default: None - SCHED will stop if not given for first scan.

Usage: Defaults to previous scan.

Example: YEAR=1996