AIPS quarterly report (Q4), Jan 04 1999 --------------------------------------- Personnel --------- There are ~4.5 full-time equivalent employees in the AIPS group. 15OCT98 ------- The 15OCT98 version of AIPS has been distributed to over 152 sites, running Solaris, Linux, DEC Alpha, HP and SGI versions. The overall number of AIPS installations has grown over the last two years; 15APR98 was one of the most widely-distributed versions ever. The majority of AIPS distributions are now received by ftp, although the CD-ROM distribution is growing rapidly in demand. One attractive feature of the CD ROM is the ability to use the binaries directly from the CD, keeping only data and a small footprint (10MB) on the processing machine. This is particularly attractive for laptop computers. The TST version of AIPS (15APR99) is currently distributed nightly to 26 sites throughout the US, Europe and Japan (22 automatically, 4 on request). Full support for SVLBI processing has been available since 15APR98. Hardware -------- AIPS running on Linux PCs continue to show impressive absolute and cost-relative performance. The best AIPSMARK so far is 14.5 when a 450 MHz Pentium II system is configured with 256MB of memory. A new benchmarking suite will need to be produced within a year or two to more adequately measure the performance (current suite now completes in under 5 minutes, which may be too short to be representative). Documentation ------------- The AIPS Cookbook has been translated from Tex to Latex, enabling conversion of the master Cookbook text to HTML (to begin Q1 1999). We are considering placing the entire AIPS documentation system (Cookbook and all help documentation) on-line with full indexing and cross-referencing during 1999. Tasks to manipulate AIPS help files within browsers are now available in 15APR99. General developments -------------------- Calibration transfer - The VLBA correlator can now automatically attach flagging, system temperature, weather, gain curve and phase cal information to VLBA data sets. Detailed revision of the definition of the data tables and of the reader routines in FITLD was required to enable in-house testing of this capability. The format definition for FITS interferometry data (previously VLBA memo #108) has been re-released as AIPS memo #102. The accuracy of SNR estimates for fringe-fitting in the tasks FRING and KRING have been improved by Ketan Desai, as described in AIPS memo #101. A bug involving INTEGER*2 arithmetic in a number of subroutines when compiled with the Linux EGCS g77 compiler (Version 1.1 and above) was found. This bug silently corrupts data when writing out FITS files using Linux. These routines have been modified in 15APR99. Hanning smoothing of cross-correlation spectra was added to minimize the effects of errors seen in the case of CVEL shifting of strong narrow spectral lines in narrow-bandwidth data. A new task TECOR performs ionospheric Faraday rotation and dispersive delay corrections using maps of the free electron content of the ionosphere received in standard IONEX format. Full support for dispersive delay corrections into the calibration routines has been added. All table headers keywords within AIPS are now stored/written as REAL*8 variables to avoid precision loss. Image sizes throughout AIPS are now fully parameterized; the system can now deal with images of 16384 pixels on a side. A new verb to show the TAPE definitions for any AIPS session has been added. Eventually this verb will inform the user if tapes drives on remote machines are available. The new task UVCON will generate a u-v database for an interferometric array whose configuration is specified by the user. Visibilities corresponding to a specified model, and Gaussian noise appropriate for the specified antenna characteristics are calculated for each visibility. The array geometry can be specified in three different coordinate systems: equatorial, local horizon, and geodetic. There is an option of using set of different frequencies to improve UV coverage. A serious bug affecting the w-term correction of visibilities when imaging fields distant from the phase center was fixed. This bug occurred if the first channel of a u-v dataset being imaged was not at the reference frequency of the file. A more complete description of this error can be found in the upcoming NRAO newsletter. A patch for 15OCT98 will be produced. Note, this bug was introduced sometime before 1990.