[evlatests] 2007-04-26_0556_POINT.txt

[Ken Sowinski]

On Thu, 26 Apr 2007, VLA Operations wrote:
> ************************************************************************
>
> Filename:       2007-04-26_0556_POINT
> Program:        POINT                Subarray(s):          1
> Observer(s):    Operations           Operator(s):          Tom Briscoe
> Date:           04/26/2007           Configuration:        D
> User #:        64                    Decommissioned:       11
> Source File(s): SYSPTX2H             VLBI Ref. Ant:
> Observing Mode: Continuum            VLBI Antenna Pad:
> Email Address:  ptg/bl
>
> ** Weather Information **
>
> Time (IAT)         Dew Pt   Temp   Wind              Bar. Press    API
> 26Apr 05:56:05     -9.6     8.5    W at 2.9 m/s      787.3         12.1

This ad hoc popinting run was undertaken to see try to refine
the pointing for antenna 21 and was successful.  Tilts changes
have been applied to the pad DE9, az offzet and el collimation
were applied to the antenna.


A new curiousity was seen in this pointing run which has existed
for a while without notice.  Antenna 14 has had a sudden change
in collimation at X band after about a year of boring stability.
The antenna has not moved and neither pointing nor rotation
parameters have been modified.  I have made no changes yet.  An
interband collimation check would be useful to see if only X band
is affected or all bands.

An historical check of pointing runs shows that the change occurred
between pointing runs on March 24 and April 2.  There was a
collimation pointing check on April 18, but antenna 14 was not
working that night.  The shift has been more or less stable since
it was first measured on April 2.

The magnitude of the shift is about +0.5 arc-min in elevation and
about -.25 arc-min in azimuth.  Does anyone remember anything
done to antenna 14 in the week between March 24 and April 2?