3.3 Station Catalog and Locations Catalog

SCHED uses a catalog to get station information such as names, positions, horizons, slew characteristics and more. This catalog is in keyin format. Station positions may be stored separately in a Locations Catalog. There are standard Station and Location Catalogs which will almost certainly have all stations used by a project. SCHED will find these catalogs by default or their locations may be specified. Any or all of the Station Catalog entries may be given in the main SCHED input if desired. In any case, the scheduler should consult the catalog to be sure that the right station names are being used in the schedule. The catalog associated with this release of SCHED is at $SCHED/catalogs/stations.dat.

SCHED input parameter STAFILE is used to point to any desired external catalog. A file name of up to 80 characters can be specified. The default is the standard catalog for digital backends:

STAFILE=$SCHED/catalogs/stations_RDBE.dat. Eventually that will be set back to STAFILE=$SCHED/catalogs/stations.dat once the conversion of documentation and examples is complete.

Station catalog information can be given in the main SCHED keyin file. If the keyword STACAT appears, all input after the next “/” is assumed to consist of station catalog entries until a line containing the keyword ENDCAT and a “/” is encountered (don’t combine this keyword with a catalog entry). Such “in-line” catalogs must appear in the SCHED keyin file before the all of the input for the first scan is complete. This allows the use of station codes to specify stations in each scan.

Both in-line catalog entries and an external catalog may be used for the station catalog. This would mainly be useful if there is a non-standard antenna in the schedule. That antenna’s parameters can be put in the in-line catalog while all other antennas are picked up from the external catalog. If you wish to prevent SCHED from looking in external catalogs, specify STAFILE=NONE.

It is only necessary to give one of X, Y, and Z or ELev, LAT, and LONG. The missing set will be calculated. If both are given, the provided values will be used. If a conversion is done, the WGS84 ellipsoid is used and the calculations are accurate at the cm level. Since WGS84 is tied to the ITRF, this should be a good way to convert GPS coordinates to the Earth centered coordinates used in VLBI.

Some of the information that can be given in the station catalog can also be provided through a locations catalog. This is mostly position information. The locations catalog can be specified by LOCFILE. See the description of that parameter for a list of the station parameter that can be in the locations catalog. SCHED will read and store the locations catalog before reading the stations catalog. If the station position is missing from the stations catalog, SCHED will search for a station in the locations catalog with the name specified with DBNAME in the stations catalog. If a match is found, the associated coordinates will be used. The locations catalog is used because, in the standard catalogs, the station locations are from the VLBA correlator data base while all the other information is from other places. It is much easier to maintain separate catalogs. Users will probably not need to worry about all this, except perhaps to specify LOCFILE if they keep the SCHED standard catalogs in a non-standard place.

The parameters of the station catalog are given below. Items that can be in the locations catalog are noted. Lower case letters are optional. Entries for a station in the Station Catalog are terminated with a “/”.

Version and station names:

VERSION:
Catalog version. Actually set to the date when all the master catalog segments were last gathered to form a full catalog.
STAtion:
Station name. Up to 8 characters.
STCode:
Station code. Up to 3 characters. Usually there are 2 characters. See Appendix A.1 for a list of codes.
DBNAME:
The station name used in the VLBA correlator data base. Might not be the same as STAtion. DBNAME is used to associate entries in the locations catalog with station catalog entries. SCHED uses STAtion for almost everything else. This name distinguishes each pad of the interferometers. There is a matching parameter with the same name in the locations catalog. Up to 10 characters.
DBCODE:
The station code used in the VLBA correlator data base. May not be the same as STCode. SCHED uses STCode for almost everything. This code distinguishes each pad of the interferometers so contains more information than the usual 2 letter codes given in STCode. Can be put in the locations catalog.

Station location:

FRAME:
A character string indicating the origin of the station location information. Can be put in the locations catalog.
ELev:
Station elevation in meters above (mean?) sea level for geodetic coordinates or meters from the center of the Earth for geocentric coordinates; these cases are distinguished by value magnitude.
LAT:
Station latitude, either geodetic or geocentric. The format is dd:mm:ss. Positive in Northern Hemisphere.
LONG:
Station longitude, either geodetic or geocentric. The format is ddd:mm:ss. Positive in Western Hemisphere.
ZALim:
Zenith angle limit in degrees. Can be used to limit elevation coverage for stations with other than AZEL mounts. The antenna will be assumed to point below this limit to whatever limits are specified with AX1LIM and AX2LIM for purposes of slew calculations. However, if the antenna is below this limit, the source will be considered to be down during any optimizations.
X:
Station X coordinate in meters. This is in the direction of the Greenwich meridian. Can be put in the locations catalog.
Y:
Station Y coordinate in meters. This makes a right handed coordinate system with X and Z. Can be put in the locations catalog.
Z:
Station Z coordinate in meters. This is in the direction of the north pole. Can be put in the locations catalog.
DXDT:
Station rate of change of the X coordinate in meters per year. Can be put in the locations catalog.
DYDT:
Station rate of change of the Y coordinate in meters per year. Can be put in the locations catalog.
DZDT:
Station rate of change of the Z coordinate in meters per year. Can be put in the locations catalog.
EPOCH:
The epoch in MJD at which the X, Y, Z coordinates apply. In other words, when the offsets due to the rates is zero. Can be put in the locations catalog.
DEScrip:
Any text up to 80 characters (not used by SCHED).

Hardware types:

CONtrol:
Telescope control file type. VEX files are produced for all projects because most antennas are converting to using them for telescope control (including the VLBA) and most of the correlators (DiFX, JIVE, MarkIV) need such files to control correlation. Other CONTROL options imply that other format files are written in addition to the VEX file. Valid option are VLBA for VLBA control files, VEX for stations that don’t need any other formats, VLA for VLA observe files (obsolete), NONE for no control file - the default. A ’V’ in the 5th character will cause a VLBA control file to be produced with only the DAS (Data Aquisition System — BBC’s, formatter, recorder etc) parameters. It is meant for cases with a VLBA style VLBI backend, but something else for telescope control. If the first 4 characters are VLBA, this will be the only file. If they are something else, both the other type of file and the reduced VLBA file will be produced. This is the default when CONTROL = VLA.
DAR:
Gives the type of Data Acquisition Rack present. This is mainly to identify the type of formatter is at the station which will let the program know about the capabilities available. Valid types are: VLBA, RDBE, RDBE2, DBBC, MKIV, VLBA4, MKIII, S2, K4, K5, VERA, VSOP, LBA and NONE (the default). Note that for Mark II scheduling (now obsolete), any site scheduled will be assumed to have Mark II equipment. The main non-obvious option above is VLBA4, which is a VLBA DAR but with a Mark IV formatter installed. This will have VLBA BBC’s and IF switching, but Mark IV formatting characteristics. The RDBE and DBBC are digital systems containing FPGA chips that can support multiple personalities. Those personalities are specified in the setup file since they can change between schedules, or even scans. The personalities are specified with DBE setup file parameter.

The RDBE2 option is the same as the RDBE except that the presence of 2 RDBE units is assumed allowing twice as many channels with the DDC personality. To use 2 RDBEs with one MARK5C unit required the use of the VDIF format which is not yet available for the PFB personality. Also the PFB personality puts out a fixed 2 Gbps which is twice the capacity of the current MARK5C recorders.

DBBCVER:
Gives the version of the DBBC. Currently supported versions are:
RECORDER:
Gives the type of tape recorder(s) present Valid options are: VLBA, MKIV, VLBA4, MKIII, S2, K4, K5, VERA, VSOP, MARK5A, MARK5B, MARK5C, and NONE (the default). The VLBA4 option is for VLBA recorders which have been modified for 16 Mbps per track operation and can be equipped with 2 recording heads. They are usually associated with MKIV or VLBA4 DARs.
NBBC:
Tells SCHED how many BBC’s or VC’s are at the site.
NDRIVES:
Gives the number of tape drives at the sites. Most have only 1 but all VLBA sites, for example, have 2. This can be overridden for a schedule using the NDRIVES parameter in the tape initialization information. Note that, even with Mark5A disks, this may need to be set to 2 to allow 512 Mbps recording, which requires two heads or two drives to give 64 tracks. NDRIVES should be the maximum number of drives at the station. If less are in service, the tape initialization input, NDRIVES can be used to specify the smaller number. For S2 sites, NDRIVES should be the number of individual recorders.
NHEADS:
Gives the number of recording head blocks on each VLBA or MKIV drive. This will be useful mainly for MKIV (and VLBA4) which will at some point have 2.
DISK:
Used to indicate that a disk based recording system is available at the station. Which system to use depends on the value of the MEDIA parameter in the tape initialization information. For VLBA systems, commands for both RECORDER and DISK can be included in the control file. Valid arguments to DISK for now are restricted to MARK5A, MARK5B, LBADR and NONE (the default).
MEDIADEF:
Gives the default recording system to use. It can be overridden by MEDIA in the TAPEINI section. The options are TAPE and DISK. This is meant to facilitate VLBA operations during the transition from tape to disk.

Horizon:

HOR_AZ:
Up to 200 azimuths at which horizon elevations are given in HOR_EL.
HOR_EL:
Up to 200 elevations for the horizon at the azimuths specified by HOR_AZ. SCHED’s down, rise, and set notes will take these horizons into account. They will also be used in the optimization mode.

Mount details and performance:

MOUNT:
The type of mount. SCHED uses this, along with the axis limits and rates, to calculate slew times. The understood options are ALTAZ, EQUAT, XYEW and XYNS. Note that XYNS is for an XY axis system with the fixed axis in the north-south direction (for example, Fairbanks). XYEW is for the other orientation (for example, Hobart).
AXISTYPE:
The axis type as recorded in the VLBA correlator data base. There are different keywords here than for MOUNT. Some day this should be cleaned up. Can be put in the locations catalog. Will go to the VEX file.
AXISOFF:
The axis offset in meters. Can be put in the locations catalog. Will go to the VEX file for correlation.
AX1LIM:
The slew limits for the first axis which is usually azimuth, hour angle or X. The units are degrees for azimuth or X and hours for equatatorial mounts. There are up to 3 pairs of numbers giving the lower and upper limits for 3 different parts of the sky. This is required to describe the limits for the 140’ at Green Bank and for XY antennas such as Hobart. Only the first set will be used for altaz antennas. For altaz antennas, the zero for azimuth is to the north and positive is clockwise looking down on the antenna. For XY antennas, positive is to the north or east.
AX2LIM:
The slew limits for the second axis which is usually elevation, declination, or Y. The units are degrees in all cases. There are 3 pairs of numbers which define the three parts of the sky over which the 3 pairs of AX1LIMs apply. The ranges for altaz antennas should not overlap, although they can touch. For XY antennas, overlaps are ok.
AX1RATE:
The slew rate for the first axis in degrees per minute for all mount types.
AX2RATE:
The slew rate for the second axis in degrees per minute.
AX1ACC:
The acceleration for the first axis in degrees per second squared for all mount types. If one value is given, it is assumed to apply to both acceleration and deceleration. If two values are given, the first is for acceleration and the second for deceleration (although for the calculations, they are interchangeable).
AX2ACC:
The acceleration for the second axis in degrees per second squared. If one value is given, it is assumed to apply to both acceleration and deceleration.

Scan timing information:

TSETTLE:
The time in seconds (or mm:ss etc) to add to the slew time for dwell time scheduling to determine when the antenna is ready to observe. This will include any computer overhead, and time to make calibration observations. Acceleration and deceleration will be calculated explicitly if the above acceleration parameters are provided in the station catalog.
MINSETUP:
The minimum interval between scans when using dwell time scheduling. If the slew time plus the settling time drops below MINSETUP, MINSETUP will be used as the interval between scans. This is required because some antennas have a minimum scan setup time but the actions that take that time can overlap with the slew. When the slew is long, the extra time does not need to be added.
TSCAL:
Lets SCHED know when the station measures system temperatures. Arguments are text of 4 characters. The viable options so far are “gap” and “cont” that indicate the system temperature measurements, or at least cal measurements, are done in the gap between scans or continuously during observing. The VLBA uses an 80Hz cal switch and measures cal-on and cal-off powers from which, using a known cal temperature, the system temperature can be derived. Typical field system controlled stations fire the cal once at the start of a scan and measure the on and off power. SCHED will warn if there is inadequate time to do this if TSCAL=GAP, but not when TSCAL=CONT. This facility is still not fully installed as of Nov. 5, 2008.
MAXSRCHR:
The maximum number of sources per hour. This is originally intended to enable enforcement of the limit in the number of slews per hour on the Mark1 telescope at Jodrell. They are very worried about fatigue and will refuse to run fast switching schedules. The default is 1.E6 which should be more than anyone would try to schedule.
TLEVSET:
This is a time to be added to the slew calculation to allow for the set-and-remember power level adjustments that happen on the VLBA (RDBE) or VLA the first time a particular setup is seen. Like MINSETUP, the time can overlap with slews so functionally, this parameter acts exactly like MINSETUP but only for the first scan with a particular setup. The VLBA needs 15 seconds. The VLA needs 60 seconds. As of Nov. 2012, the VLA actually needs this every time there is a slight frequency change (like new Doppler shift), but we will try to get that changed to be only for more major changes. Note that, if the first scan with a setup is non-recording, non-pointing, and non-phasing, the scan itself will be accepted as the level setting (DUMMY on the VLA) scan. This allows for explicit insertion of DUMMY scans.

Below is a sample entry from the RDBE based version of the standard station catalog. The full catalog a can be examined here for the version that uses MARK5A at the VLBA and here for the RDBE based version.

 
 STATION=VLBA_MK   STCODE=Mk  CONTROL=VLBA  
    DBNAME = MK-VLBA  
    MOUNT=ALTAZ  AX1LIM=-90,450 AX2LIM=2.25,90 AX1RATE=86.8 AX2RATE=28.3  
    AX1ACC=0.75  AX2ACC=0.25  
    TSETTLE=6 TLEVSET=5 MINSETUP=5  DAR=RDBE  NBBC=16  
    DISK=MARK5C   MEDIADEF=DISK    TSCAL=CONT  
    ! MK    From 150 K Ts line by Beasley and Medcalf  Aug 1992.  
    HOR_AZ =   0,  5, 10, 15, 20,120,125,130,135,140,145,150,155,160,  
             165,170,175,185,190,195,200,205,210,215,220,255,260,270,  
             275,280,285,290,295,300,305,310,315,320,325,330,335,340,  
             345,350,355,360  
    HOR_EL =   5,  4,  3,  3,  2,  2,  4,  5,  5,  4,  4,  6,  8,  8,  
              11, 12, 13, 13, 11, 11,  9,  7,  5,  3,  2,  2,  3,  3,  
               5,  6,  8, 10, 12, 14, 12, 11,  9, 10, 11, 10, 12, 14,  
              12,  9,  7,  5  
  /