[evlatests] 3-bit polarization/stability test

[Rick Perley]

    Ahh -- forgot about that. 

    O.K. -- tomorrow night?!  (with luck, we'll have another 3-bit 
antenna outfitted?)

    Rick

Scheduling Officer wrote:
> The EVLA is doing fixed-date observing until about 930pm tonight. - Joan
>
> EVLA/VLBA Scheduling Officers
> schedsoc at nrao.edu, NRAO, Socorro, NM, USA
> http://science.nrao.edu/facilities/evla/schedules/schedsoc
>
> On Tue, 8 Nov 2011, Rick Perley wrote:
>
>>    ... was going to send this to specific individuals ... but it's
>> easier to do it this way ...
>>
>>    We talked yesterday about a longish observation of OQ208 for the
>> main purpose of determining variability of the antenna/electronics
>> polarization.  There are worries about temperature sensitivities, so an
>> observation of a source through dawn was felt to be optimum.  The
>> previous test was of 3C286, which has the distinct disadvantage of being
>> very highly polarized, making it difficult to isolate small
>> antenna-based effects.   Polarization tests are much better done with a
>> strong unpolarized object.
>>
>> Unfortunately, at this time of year, the highly preferred source -- 3C84
>> = 0319+4130 (30 Jy) is an evening source, so OQ208 = J1407+2827 seems
>> preferred.
>>
>>    But I think 3C84 should still be utilized, and the test be done in
>> late afternoon-evening, when temperature differentials are nearly as
>> strong as they are in the morning.  3C84 rises just before sundown.  The
>> maximum rate of change of temperature in the vertex room is likely to be
>> during these evening hours.  I suggest we do this *tonight*, and that we
>> use Ku-band.  Amongst other things, we know the polarizer purity at
>> Ku-band is better than at X-band, -- making electronics polarization
>> changes even easier to detect.
>>    One of the distinct advantages of 3C84 is its very high flux density
>> -- 15 times that of OQ208.  This is very useful in finding other issues,
>> and measuring -- for example -- the bandpass stability.
>>    It is now clear at the site, and the winds are lightening up.  A
>> nice calm and frosty night is forecast.  It's a good time for this test.
>>
>>    Rick
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