The 15APR99 version of AIPS is under development at the present time. It is run as the TST version at all NRAO sites and at a variety of other sites around the world. Changes in this version are installed on a (nearly) daily basis by the so-called midnight job. This may be run once a copy of 15APR99 is installed. There have been a number of changes to IMAGR, a variety of bugs in calibration were fixed, FITLD was improved, and a better way to write FITS-format output was created. Among the changes made to AIPS for 15APR99 are:
1. FITLD for VLB: a. New proc MERGECAL to merge redundant information created when calibration transfer data are concatenated. b. Corrected handling of BIF, EIF, BCHAN, ECHAN which were honored even if crazy (e.g. BIF of 3 in a 2-IF data set). c. Corrected handling of input tables to conform to new standards for the contents of these tables and to allow some older variations. Also changed to allow, with warnings, data out of time order. 2. CVEL - new option to control whether Hanning smoothing is used. This is a good idea if there are narrow lines. Otherwise, the shifting will produce ringing in the spectrum. 3. Fringe fitting: a. Corrected bug that kept FRING from looping correctly over subarrays and a bug that caused it to die when rate-only solutions failed. b. MBDLY now has FREQID and SUBARRAY adverbs, allowing more than the first of each to be used. c. KRING copies multi-band delays properly to all IFs. It uses a new scheme for computing SNRs detailed in AIPS Memo 101. KRING has been extensively tested using a new test data set created by DTSIM and compared with FRING. KRING runs faster in many cases, uses less memory, is able to handle larger problems then FRING. MBDLY frequently does not converge on correct answers.
4. Calibration errors found: a. Since 1992, old calibrations were carried forward rather than being replaced by failed solutions (with the output data blanked). b. Faraday rotation corrections were not initialized properly. c. Calibration was not updated often enough for good antennas when some antennas had large gaps between solutions (1998-08-12 through 1998-10-17). d. Dispersive delay corrections are now done of there are non-zero values in the DISP 1 column of the CL table. e. QUAL and CALCODE are now used to select a list of sources some of which are selected or de-selected with the SOURCES adverb. f. 1.0 is no longer subtracted from autocorrelation data when bandpass calibration is applied. g. Calibration was not interpolated when the calibration values were updated unless the time also changed by "enough"; changed to force an update. 5. FITAB - new task to replace FITTP gradually. It can write more compressible image FITS files by allowing the user to control the quantization (scaling to integer form). It writes uv data in binary tables forms, optionally writing them as compressed data (like on disk) and in pieces. The former saves space while the latter provides better recovery from media error (e.g. parity, end-of-tape, etc.) Older FITS readers can read the images produced, but cannot read the uv data tables form. Please try FITAB, but not when you are taking the output to 15OCT98 or older AIPS versions or to packages such as difmap. 15APR99 versions of PRTTP, UVLOD, and FITLD can handle the new table format and PRTTP can now report on disk files. 6. TECOR - new task to perform ionospheric Faraday rotation and dispersive delay corrections using maps of the free electron content of the ionosphere in standard IONEX format. 7. CLCOR - The source position correction had its parameters changed. 8. FLGIT - Changed meaning of APARM(4 and 5), changed FLAGVER defaults, improved displays. 9. PRTUV - new adverbs were added to allow the user to specify scaling parameters so that the task does not have to spend time determining them. 10. ACFIT - was corrected to handle any size of input problem, to write correct REFANTs to the output, and to count output samples correctly. 11. UVCOP now does a better job of deleting flagged data when IF or channel selection is being done. 12. UVCON - new task to generate a uv database for an array configuration specified by the user.
13. IMAGR - a. Changed to finish a full major cycle even if NITER is exceeded. b. Corrected bug in doing primary beam correction for multiple fields and fixed it to handle coordinates correctly even or 3D imaging. c. IMAGR, REBOX, and FILEBOX can now display boxes which are not completely on the visible TV area and revise only those that are fully visible. d. OVERLAP 2 is very useful and is now allowed without requiring DO3D to be true. This mode uses a modified scheme for selecting the next field to Clean which will avoid the Cleaning of noise fields to some extent. e. The gridded subtraction of Clean components has had an error for a very long time. The W term was not handled correctly when the first channel to be subtracted was not at the reference frequency. Using BIF > 1 or the primary beam correction could cause significant degradation in the quality of the subtraction in some cases. f. OBOXFILE is a new option to write out the Clean boxes set interactively in IMAGR and SCMAP. 14. Images may now be up to 16384 on a side, a parameter which should be honored throughout AIPS. 15. FLATN - has another adverb to delete pixels around the edge of each input image. Changed it to use windows to speed up the operation.
16. TAPES - new verb to display what tapes are available on the local or on a remote host. It will even try to go to a remote TPMON over the Internet to get this information if it is not available locally! (Of course, it works only to 15APR99 sites.) 17. The use of INTEGER*2 was reduced in AIPS to the minimum possible since it is a source of compiler error (e.g. the newer egcs compiler versions). 18. XAS no longer has a small uninitialized row at the bottom of the screen.
The 15OCT98 version of AIPS is the standard "release" now available to all sites. See the release notes for details on how to get a copy. The release is described in the 15OCT98 AIPSLetter. Among the changes made to AIPS for 15OCT98 were:
1. FITLD improvements: a. Calibration transfer from the correlator into AIPS data sets has been implemented. It should no longer be necessary to copy log files into text files which are then read into AIPS. See Chris Flatters' memo or web page for details:(memo) (web page)
b. The computation of the reference frequency for lower sideband data was corrected. c. The renumbering of sources was improved to avoid excessive source numbers and confusion over CALCODEs. 2. Fringe-fitting in KRING was improved a. to attempt forward and backward extrapolation of solutions in order to avoid excess computation. b. The SNR is now computed in a new and self-consistent way For details, see Ketan's(AIPS Memo 101)
3. Delay calibration was not previously applied if it was zero for the first IF/channel. Now all values are checked and used.
4. SPLAT - is a new task to apply calibration and average the output over time and/or spectral channels. 5. SPLIT - was revised to average spectral channels after calibration, to handle multiple subarrays as advertised, to count samples better, and to omit the REMOVED random parameter. 6. The interactive editing tasks (EDITR, EDITA, SNEDT and the editing in SCMAP) were revised to allow editing in crowded displays and to provide a number of other improvements in the speed with which data may be flagged. 7. Numerous errors in BPASS were corrected. Channel-dependent data flagging led to improper weighting of channels, bad interpolation across missing channels and other problems. The application of BPASS solutions from autocorrelation data to cross-correlation data and vice versa was fundamentally in error. A missing antenna in an AN table caused addressing failures. 8. FLGIT - is a new task to remove RFI-affected samples from low-frequency, multi-channel data sets. 9. UVCOP can now apply up to 50,000 flags at a single time (ten times more than the rest of AIPS). 10. Times in SN and CL tables no longer need to be the same for all antennas.
11. CONFI - is a new task to optimize array configuration designs. 12. The NVSS web site may now be used to prepare field parameters for input to IMAGR. SeeNVSS AIPS tool
13. FLATN can now apply geometric corrections while flatten a 3D multi-field set of images. 14. Radial bandwidth smearing corrections are available in SAD, IMFIT, and JMFIT. 15. OMFIT has steadily acquired the ability to model the universe.
16. XAS is now able to do 24-bit TrueColor displays on monitors which support such things. This allows true 3-color images and full hue-intensity displays. 17. Split screen and roam were added to XAS as well. They work best in the 24-bit mode but are usable in 8-bit. 18. You may now have as many TV displays, message terminals, etc as you want. Only one may be connected to the Internet but one can have 1 or more local Unix socket displays. This means that XAS runs on the same computer as, for example, IMAGR and AIPS. The images may appear on any computer or X-terminal display selected by the $DISPLAY variable. 19. Printing to the terminal may be set to detect the size of the current terminal (e.g. xterm) window and to pause when that size is filled. Previously, the official window size was stored in a file and the actual size was ignored. 20. POPS now has a much larger area for storing procedure, new variables, etc.