[daip] draft VC report for comments

[Eric Greisen]

          Visiting Committee Report on AIPS

                  02 March 2004

The 31DEC03 version of AIPS was developed through 2003 and then frozen
in late December.  It was available for download (and update via the
"midnight job") during development and the frozen version may now be
downloaded.  The new test version, 31DEC04, was started in December
2003 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 551 sites in 2003 and from 251 sites so
far in 2004.  We started counting downloads in May 2003.  Since then,
the frozen 31DEC02 version was downloaded by 88 sites and the 31DEC03
version, while under development, was downloaded by 416 sites.  At
this writing, the frozen 31DEC03 version has been downloaded by 81
sites and the development 31DEC04 version has been downloaded by 217
sites.

We have found that the GNU 3.2.2 version of the compilers, which is
shipped with RedHat 9, works reasonably well so that AIPS users can
get out of the compiler-installation game, at least with Linux  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.  Unfortunately, IBM has begun to charge for their
compiler.  We are looking into ways in which NRAO might provide
binaries, generated by this compiler, rather than forcing all
MacIntosh users to spend the non-trivial cost for the IBM compiler.

The installation script continues to be improved as various minor
problems are encountered.  The largest change was to allow a machine
to be called a "laptop" in order to avoid problems caused by the
machine's name apparently changing every time it is plugged into a
LAN.  The code was revised to accept read-only file systems, thereby
allowing DVD media written on +RW drives to be used on read-only
drives.

Steps are being taken to support greater use of pipeline and other
procedures in AIPS.  The set of procedures to reduce VLA data in a
pipeline was introduced.  A new task, RLDIF, was written to determine
the right minus left phase difference and return it to procedures to
allow the polarization calibration to be completed.  Other tasks such
as model-fitting tasks were modified to return their results for use
in procedures or verbs.  The separation between input and output
adverbs was clarified; INPUTS no longer displays output-only adverbs,
OUTPUTS is required.

The calibration and fringe-fitting tasks were given the ability to
determine solutions in time intervals that overlap.  This should
resolve lobe ambiguities while giving adequate signal-to-noise.  The
main flux calibration task now uses the source "V polarization" to do
different calibration for the RR and LL polarizations.  This will be
used for WSRT data primarily, where "V" is actually Stokes Q and
"RR/LL" are actually XX/YY.  The tasks which smooth solution tables
and interpolate them to calibration tables were generalized with
greater user control added and a few bugs removed.

A new task, DELZN, was written to determine residual zenith delays and
clock errors from observations of phase calibrators over multiple
angles in the sky.  This task can apply the corrections to the
calibration table.  Another new task, DFCOR, can apply these
corrections in a differential fashion for rapid phase-referencing
observations.  The VLBI calibration task APCAL was improved
substantially in its ability to estimate and correct for atmospheric
opacity, using the weather data which now comes with all VLBA data
sets.  VLBA observations using the VLA as one of the stations are now
supplied with a full set of calibration and weather information for
the VLA station.

The use of color in AIPS plots was enhanced even more.  Plot tasks may
now draw lines in any color they choose.  The tasks PCNTR and KNTR
were given options to let the spectral channel control the color of
contour drawings and to let the position angle control the color of
polarization vectors.  The latter allows the viewer to see the
position angle even when the vectors are too short for accurate
estimation of their directions.  Other tasks now use full color to
separate symbols plotted for different spectral channels, IFs, and/or
polarizations.

A few new verbs were written to assist in plotting on the TV, using TV
colors in plot files, and resetting coordinates.  Three new tasks were
written to allow users to remove source name and qualifier information
from a data set and to discard the cross-hand polarizations.  Two new
tasks were also added to assist array configuration studies, one to
estimate loss due to shadowing and the other to convert formats
primarily for site masks.