2001 January 1-March 31 AIPS Quarterly Report
                                
AIPS
     Versions - In December 2000 and January 2001, a version of AIPS, christened 31DEC00, was
frozen and released.  This release, available on CD or via ftp, was necessitated by the implementation of
a number of new features, and the reluctance of users to sign up for the regular Midnight Job.  The
current test version is 31DEC01.  Although a frozen release takes considerable effort, the plan is to make
one release per year in order to prevent the versions at many external sites from getting too out of date.
     The 31DEC99 version, "AIPS for the Ages," was distributed 407 times via ftp.  Through the first
quarter of 2001, there were 116 distributions of 31DEC00 (90% ftp) and 158 ftp's of 31DEC01.  About
60% of the registrations for the newest versions are on Linux architectures.
     Personnel - Chris Flatters left the AIPS group in late 2000, and Eric Greisen moved
"permanently" to Socorro, where Jim Ulvestad now heads the AIPS group.  In January 2001, Amy
Mioduszewski joined the AIPS group, with a focus on providing VLBI support and extending the
procedures for VLBA data reduction in AIPS.
     Key Developments - 
               1.   Large-file support (greater than 2 Gigabytes) has been tested, as supported under version
          2.4.2 of the Linux Kernel.  Tests using wide-field VLA mapping at 74 MHz have been
          successful.
               2.   New procedures have been developed to carry VLBI data calibration all the way through
          fringe-fitting, the last step prior to imaging and self-calibration.  Procedures that take the
          users through the initial amplitude calibration are available in 31DEC00, while the
          additional delay-calibration steps (pulse calibration and fringe-fitting) require a recent
          version of 31DEC01.  The first release of AIPS Memo No. 105,   "AIPS Procedures for
          Initial VLBA Data Reduction," covers the procedures available in 31DEC00.  These
          procedures are accessed via the runfile VLBAUTIL.  
               3.   The CROSSPOL procedure, which calibrates polarization leakage terms for VLBI
          observations, was modified to increase the robustness by removing hidden variables.
               4.   The task CONFI, used for simulations of possible ALMA configurations, has been
          expanded to handle as many as 2000 antennas, enabling use in configuration studies for
          the Square Kilometer Array.
               5.   FITLD was modified to recognize correlators other than the VLBA correlator, and turn
          off all VLBA-related options that are incorrect for the other correlators.
               6.   BPASS was modified to correctly shift spectra from the center of the Earth to the
          locations of the antennas on the surface of the Earth.
               7.   Algorithms for plotting fields including the North and South Poles were fixed to provide
          more accurate right ascensions and meaningful tick marks.
               8.   Modified tasks SETFC and FACES to provide more flexibility in multi-field imaging.
               9.   Small errors corrected in a number of tasks.
     Goals for Q2 2001 -
               1.   Continuing maintenance and user support.
               2.   Install large-file support on all Linux machines in Socorro.
               3.   Revise documentation for VLBA data-reduction scripts.
               4.   Complete error tests for Gaussian fitting routines.
               5.   Low-level code development in support of NRAO instruments.