VLA Test/Observation Coordination Meeting
                           B.G. Clark
                       September 18, 2003


1.  Polarization beams

T. Cornwell notes that in some practical cases images may be severely
affected by sources far from beam center which are not properly 
removed by the commonly used procedures because they do not take 
proper account of the variation of instrumental polarization across
the beam.  The beam squint is sufficiently large that merely correcting
by the average beam does not suffice.  And the linear polarization
of a source, interacting with the linearly polarized instrumental 
variation, can produce artifacts in the intensity map.  TC is producing
software which will do a better job, but this software requires a good
estimate of what the instrumental variation across the beam actually
are.  He is looking into this using data from R. Perley taken for 
holography purposes.  At all bands, far from the center of the beam
the patterns display complex behavior without radial symmetry.  Within
more comfortable parts of the beam, the expected radial symmetry appears
to dominate, except at C band, where the pattern is curious and 
unexpected even well within the beam.  However, TC believes the 
magnitude of the polarization effect is about a factor of two higher
than predicted by W. Brisken using the GRASP8 software.

2.  eVLA

Antenna 13 has come out of the Assembly Building, and is now sitting
on the master pad.  It is slowly being equipped.  S. Durand reports 
on results from a test setup designed to measure the stability and
measurability of the optical fiber LO system.  As designed, the optical
fiber LO system merely returns some of the light from the antenna in
a second fiber, and used to measure sum of the delays in both fibers.  
The assumption is made that half of the variations occur in each fiber.
(The fibers are packaged together in a small, gel-filled tube.)  He
is investigating this assumption by establishing two round-trip circuits
from the Control Building to the antenna, and comparing their delay 
measurements.  The test setup he is using has an accuracy of only about
1ps; the eventual system will be about ten times better.  He reports
on a measurement of the the phase variation as the antenna rotates in
azimuth.  The total delay variation was modest - a few picoseconds 
during the course of the measurement, which would have included both
thermal and azimuth wrap effects.  And even more encouragingly, the
two round-trip circuits agreed with each other to within the accuracy
of the measurements.

3.  Archive retrieval

Beginning October 1, the archive retrieval tool will be open for people
to do their own retrieval.  Tools, etc. are described in
http://e2e.aoc.nrao.edu/archive/.