[evlatests] Stellar high-frequency data

[Claire Chandler]

Was your test able to say anything about phase transfer at high 
frequencies?

Claire

On Fri, 25 Jun 2010, Rick Perley wrote:

>    I ran a test last night, in preparation for the observations of the
> 'pretty-picture' of Cyg A, for the eventual commissioning.
>
>    In this test, I set up a trial run, 2 hours, cycling through K, Ka
> and Q bands, applying referenced pointing, and observing the
> flux/polarization calibrator 3C286, the local calibrator 2007+4029, and
> various positions along Cyg A (since its extend of 2 arcminutes makes it
> larger than the antenna primary beam at Q-band).   These observations
> were taken in OSRO1 mode.
>
>    The short 'executive summary' is that the data are marvelous.  Two
> 2-minute snapshots on Cyg A at K band has provided images with over
> 200:1 dynamic range, using only a few central channels.
>    I shorted the durations for each observation to 2 minutes -- in no
> case did more than the initial 15 seconds of any of these had to be
> flagged.  So there appear to be no 'setup' problems.
>
>    But things are not perfect.  I have analyzed only the K-band data so
> far (taken at 19 and 25 GHz).  Below I list the issues -- some of which
> are being addressed already.
>
>    1) Due to an oversight, the 'BD' frequencies were not observed in
> 'set and remember' mode.  This meant the table values were used, which
> caused effective loss of fringes (very weak in general)  on a number of
> antennas.  I'm using  frequency tunings near the edges of the bands, so
> there is no surprise in the result.
>
>    2) Antenna 20 is clearly not pointing correctly, with a cyclic
> response of a few minutes.  I think this is known to be a subreflector
> or encoder problem -- it would be good to hear this is being addressed
> as it affects all bands (even L-band!).
>
>    3) Antenna 22 was stowed due to an issue with IF 'A'.
>
>    4) 5.5% of the visibilities were flagged as integer 0 -- all of
> these are near the beginning of the scans.
>
>    5) There were a very few 'failures to tune'.
>
>    All in all, a very encouraging test.
>
>
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