[daip] revised BAAS draft for comment

[Eric Greisen]

     The Astronomical Image Processing System (AIPS) software is still
used by most observers to calibrate and image the data from the VLA
and the VLBA.  It is also widely used for data from other radio
astronomical interferometers.  Since this software is supposed to be
replaced by a more modern package, the manpower in the AIPS project
continues to be reduced.  In the 2000-2003 period, two full-time
scientific programmers and a part-time systems expert were "replaced"
by a scientist doing part-time maintenance/programming.  Despite
previously announced intentions, AIPS is still issued on a fixed
release schedule, which is now annual.  During the reporting period,
the 31DEC00, 31DEC01, and 31DEC02 fixed releases were made.
Statistics on the usage of these is incomplete, especially for
31DEC02.  By December 2001, 637 copies of the 31DEC00 release had been
given away, 449 before it was officially frozen.  Also by that date,
448 copies of 31DEC01 had been given away before it was frozen.  AIPS
is now administered in Socorro at the Array Ooperations Center rather
than in Charlottesville.  It was moved in December 2001 and user
access to the development version, beginning with 31DEC02, was changed
from "secure-shell" to the "cvs" code versioning system.  This has
greatly improved the reliability and simplicity of the "midnight job"
which is used by active AIPS sites to keep their version of AIPS
completely current with the version that is under active development.
That version, now 31DEC03, is updated more or less regularly by over
50 sites.

     During the period, the AIPS group has concentrated on fixing bugs
and making various minor additions to the software.  Despite the
reduced manpower, however, a variety of significant improvements in
the AIPS software have appeared in the reporting period.  They are
described in detail in documents available from the web site at
http://www.aoc.nrao.edu/aips.  The reduction of data from the VLBA has
been greatly simplified by the release of a set of procedures which
perform the basic data reading and calibration operations using
standard parameters.  A VLBA pipeline, which reads, edits, calibrates,
and even images VLBA data automatically, has been released within
AIPS.  This procedure is now run on all eligible VLBA experiments
with the results given to the observers along with their raw data.  A
similar pipeline for VLA continuum experiments has been developed and
released.  NRAO does not, as yet, run this pipeline script for the
observers.

     The VLA data filling task now uses weather data and tables of
antenna gains to provide users with initial calibration values.  It
also reads data from the disk archive as well as from magnetic tape.
Several new data editing tasks were written to flag data based on
calibration discontinuities, data decorrelation, weather, and,
interactively, on values outside the range expected by the user.
Imaging algorithms appropriate to low-frequency data from the VLA also
received attention.  Users may now prepare inputs to do multi-faceted
image deconvolution, correctly accounting for sky curvature and for
possible interfering sources found in user tables and in the NVSS and
WENSS source lists.  The latter are shipped with AIPS in a special
compact form.  AIPS plots may now be rendered in color with a variety
of options controlling line and background colors as well as pseudo
and true color "gray-scale" images.  Lines drawn on top of gray-scale
images change color when the gray-scale exceeds a user-set level.  New
verbs to assist in entering adverb values and new functions to assist
in moving data from Solaris to Linux systems were written.  Tasks may
now set adverb values in the AIPS control program.  AIPS tasks to aid
in the design of new interferometric arrays such as the EVLA, ALMA,
and the SKA have been developed and are in widespread use.  AIPS has
been ported to run on MacIntosh OS/X computers.