March 2006 Visiting Committee Report on AIPS The 31DEC05 version of AIPS was developed through 2005 and then frozen in late December. It was available for download (and update via the "midnight job" or MNJ) during development and the frozen version may now be downloaded. The new test version, 31DEC06, was started in December 2005 and is available for download and update. We have developed tools to count downloads of full AIPS versions and to count access to the main "cvs" site. The latter reflects both initial installation and updating of the development version; frozen versions do not generate cvs accesses. Counting each unique IP address as a "site", there were cvs contacts from 982 sites in 2005 of which 252 appear to have run the MNJ at least occasionally. The frozen 31DEC04 version was downloaded by 246 sites and the 31DEC05 version, while under development, was downloaded by 832 sites. A total of 1460 unique IP addresses downloaded a copy of AIPS and/or accessed the cvs site. At this writing (21 February), the frozen 31DEC05 version has been downloaded by 76 sites and the development 31DEC06 version has been downloaded by 214 sites. The total number of IP addresses is already 425. We have found that the Fortran compiler developed by IBM for MacIntosh systems generates code that is 50% faster than that produced by the GNU compilers. On Pentium IV machines, the code generated by the Intel compiler is 30% faster than that generated by the GNU compilers. In fact, The Intel-compiler binaries are also about 7% faster on non-Intel machines (AMD 64s). A similar speed up is seen with the SUN compiler on Solaris machines. Unfortunately, these compilers are moderately expensive. Therefore, we have made available binary distributions of AIPS. This binary form is available both for the frozen 31DEC05 release and the development 31DEC06 version, including periodic updates (daily are possible) via the MNJ. So far in 2006, 90 sites have accessed the binary version of 31DEC06 and 46 sites have accessed the binary version of 31DEC05. Models for the primary flux calibration sources are now provided with AIPS. There are four sources, 3C48, 3C138, 3C147, and 3C286, at the three highest VLA frequency bands, K, Q, and U. These models were provided by Claire Chandler. Lower frequency models at X, C, and L bands for 3C48 and 3C286 have been provided so far by Amy Mioduszewski. We expect, in the long run, to provide models for all four sources at all VLA frequencies. The pipeline procedures for the VLA are being revised to use these models. Steps are being taken to support greater use of pipeline and other procedures in AIPS. The new experimental task FLAGR uses the internal statistics in a data set to flag that data set. It was corrected to flag times at which it fails to find antenna-based amplitudes, phases, and weights from the baseline data. With this correction, it appears that the task is quite effective in flagging calibration sources and it is being incorporated into new pipeline procedures. The VLBA correlator requires an estimate of the Earth Orientation Parameters in order to correlate an observing session. Unfortunately, the final best estimates of these parameters are usually not available at correlation time. For a period of time, the VLBA correlator used very preliminary estimates rather than better estimates which were available by correlation time. AIPS task CLCOR was given a new option to read the final best EOP estimates and correct the data to those from the EOP values used at correlation. An AIPS procedure was written which fetches these estimates from the web and then runs this CLCOR option. Because of a shortage of disk playback units at the VLBA correlator and limitations in the instantaneous bandwidths which may be correlated, the old AIPS tasks VBMRG and VBGLU are again needed. They have had various bugs and limitations corrected and VBGLU is about to be rewritten so that no data are lost in the process. AIPS uses dynamic memory to allow for large-memory problems without burdening normal uses of quite a number of tasks. The code was revised to support those 64-bit addressing computers which allocate dynamic memory at virtual addresses well removed from the virtual addresses assigned to the pre-compiled code. AMD-64 computers under Linux are among this class and NRAO has acquired one to support this architecture in aips++ (and AIPS). Miscellaneous enhancements including generalizing all tasks which handle box files so that they support all box and field definitions used by IMAGR. The new task CCRES allows the addition or subtraction of Clean component models in images without requiring power of 2 images and point sources exactly on image cells. The remaining Tektronix emulation tasks, including XGAUS and XBASL, were revised to offer more reliable TV-based methods. A spectral-index fitting task was written and other tasks revised in anticipation of problems with spectral index over the very wide EVLA bandwidths. A spectral-index correction method is being added to IMAGR. Full information on AIPS may be found beginning at the main web page http://www.aoc.nrao.edu/aips/