March 2003 Visiting Committee Report on AIPS The 31DEC02 version of AIPS was frozen in late December, and the frozen version now is available for download. The new test version, 31DEC03, was started and now is available via the standard midnight job. Unfortunately, the lack of systems support for AIPS has prevented the re-institution of monitoring of ftp downloads of the frozen version, though it is known that over 50 different sites are running the midnight job. We continue to test each new version of Linux compiler that appears on the market, but the best performance still is found in the GNU compiler version 2.95.3. This means that AIPS sites must install this compiler together with versions that are shipped with various RedHat releases. AIPS recently has been ported to the MacIntosh operating system, OS/X, and the frequently updated 31DEC03 version is available under this port. Preliminary tests show that the performance is not as good as on the standard Linux versions; further testing is expected this year. A major multi-task development has been the institution of full color-plotting capabilities. The standard image-presentation tasks such as KNTR, GREYS, and PCNTR can produce grey-scale images (with or without contours and polarization vectors) that can be converted to pseudo-color or to standard true-color (rgb) images with a color table (OFM, or "output-function-memory"). The standard plotting task, LWPLA, has various levels of control enabling the specification of the conversion from grey-scale to color scales. Based on user specifications, contouring, labeling, and polarization vectors can change "automatically" between light and dark colors based on the brightness of the underlying background. In addition to the rgb (red-green-blue) color representation, a cmyk (cyan-magenta-yellow-black) capability also exists, which enables the direct production of color postscript files that can be used directly by many of the standard research journals. The VLBA data reduction pipeline, previously called as a stand-alone script, now has been incorporated into the standard AIPS release. See the above section on User Support and Outreach for further details. For a number of years, definition of a new "World Coordinate System" (WCS) standard has been sought under the auspices of both international and national FITS working groups, with major participation and leadership from within the AIPS group. This standard is critical for the ultimate goal of full data specification and interchange under the auspices of the planned National Virtual Observatory. We are pleased to report that the WCS standard has been approved by a vote of the appropriate FITS working groups, and the two papers defining the basic WCS specifications now have been published in Astronomy & Astrophysics. The VLA data-filling task, FILLM, has been changed to allow the reading of disk files. This will be important for use with the upcoming on-line VLA data archive. FILLM and WETHR were modified to provide more control and insight into opacity corrections that were made to the data. A seasonal opacity model was added to the one that is derived based on the actual surface weather data, and the user given the capability of combining the two with any relative weighting. The UVCON task that is used to simulate (u,v) data, particularly for configuration studies for ALMA, SKA, and EVLA, has been modified to improve its mosaicing capabilities. The various mosaicing imaging tasks (e.g., VTESS) and AIPS "include" files have been changed to permit up to 4096 fields (pointings) to be imaged. The improved task has been used to begin simulations of the E configuration to be proposed as part of Phase 2 of the EVLA Project. A variety of adjustments have been made to IMAGR and related tasks, largely in order to make wide-field imaging and multi-resolution Cleaning more robust. Included are new and improved ways to create and handle boxfiles, a bug fix in steering the multi-resolution algorithm, better defense against selection of a field with inadequate flux or bad window parameters, and an increase in the size of the Clean box arrays. A new task, WIPER, was added to provide interactive editing of data using a plot of the (u,v) data on a TV screen. Various options, for flagging data or for removing flags for data previously flagged with WIPER, are available. Finally, a new task, LOCIT, was added to enable improved fitting for antenna positions. Deriving new antenna positions after VLA reconfigurations, and implementing them in the VLA on-line system as quickly as possible, is an important activity for the scientists observing soon after antennas are moved. LOCIT makes the data analysts’ job simpler, and should result in more antennas being useful sooner following reconfigurations.