[evlatests] ea09 below 30 degrees...

[Ken Sowinski]

I haven't looked at pointing results recently because it hard to do from 
home.  But, on the face of it an effect that large suggests there might
be someting loose up at the apex.  As a pointing model error is has to
be well over an arc-min to cause consistent failures at X band.

Ken


On Mon, 25 May 2020, rperley via evlatests wrote:

> We ran the 'gain-elevation' script last night.  The purpose is to remeasure 
> the gains as a function of elevation, from X through Q bands.  The method 
> uses 'double-referenced pointing' -- referenced pointing is done first at 
> X-band, and these results are used to 'peak up' Ku-band, then K-band, then 
> Ka, and ending with Q-band.  This is to ensure the antennas as peaked up on 
> the source for each band and elevation.
>
> Observations started with the source (J2007+4029) at 11 degrees elevation, 
> and proceeded cyclically  through the bands until meridian transit.  For each 
> cycle, the old referenced pointing solutions were 'forgotten' when X-band was 
> next scheduled.  This procedure worked very well for nearly all antennas. 
> But not ea09...
>
> Something is seriously amiss with this antenna, for elevations below 30 
> degrees.
>
> All referenced pointing attempts failed, including the initial X-band one, 
> until the antennas reached 23 degrees elevation.  At this elevation, the 
> solution offset parameters looked good, but in fact were not, as the gains 
> (at X-band!) were low by 40%.  As the antenna rose, the gains rapidly 
> increased until, at elevation 34 degrees, all looked normal at all bands. 
> From then until meridian transit, all was well.
>
> I have no idea what is wrong here.  Any ideas?
>
> Rick
>
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