[mmaimcal] ACA Antenna Specs

[Mark Holdaway]

Either way (WVR's on 7m dishes,   or   spatially interpolating the
12m atmospheric phases)

we will have to introduce Yet Another Calibration Stage (YACS) to measure
the electronic phase drifts in the 7m dishes.  And we need to separate 
out the
atmospheric phase from th electronic phase on the 12m dishes so we
have something to interpolate in the first place.   AND of course, while
we are doing those extra calibrations, we are NOT taking data with
the rest of ALMA, reducing the efficiency, and increasing the software
complication.

A bloody lot of pain for a modest gain.

My 2cents:  Thank God I'm Not Going to have to DO THIS!

Thinking of a different issue, the SOLAR CALIBRATION STRATEGY,
I keep realizing "Oh, THIS will need to be done in software, Yet Another
Thing Brian Glendenning Needs to Do (YATBGND)" -- one more layer which is
conceptually not difficult, but the details will interact with other 
details.


I guess my blood sugar isn't right just now.


    -Mark

>we also, in the ACA System Design Review, pointed out that it might benefit to 
>have WVRs on the 7-m antennas, to overcome this shortcoming.  this was rather 
>coolly received, but i did my part by bringing it up...
>
>	-bryan
>
>
>On 12/14/06 15:51, Al Wootten wrote:
>  
>
>>Hi Mark
>>
>>In my understanding interpolation is the plan, for the atmosphere from the
>>WVRs on the 12ms and the instrumental part will have to be guesstimated from 
>>phase calibrator observations.  During these, of course, the 7m can benefit
>>by the many more antennas to which they will have baselines.
>>
>>In fact, the joint correlated observation mode still needs a change request,
>>to go past the change committee and through the Director.  During this
>>process we need to address questions of exactly this ilk.  As a result of the
>>process, we'll come to understand better the full cost of the 'upgrade' of
>>which software additions will be a component.  As we noted yesterday, so will
>>the lower efficiency as the array waits for the 7m upon slewing to a source.
>>But Tetsuo notes the higher efficiency in terms of 7m calibration offsets this.
>>
>>This all needs careful thought.
>>
>>Clear skies,
>>Al
>>Mark Holdaway writes:
>> > Al,
>> > 
>> > If "ACA does not fast switch", what is the phase calibration strategy for
>> > when we do joint correlated observations?  Will the ACA's 4 large dishes
>> > phase solutions be spatially interpolated for teh ACA antennas?
>> > If so, more software.
>> >  
>> >     -Mark
>> > 
>> > 
>> > 
>> > Al Wootten wrote:
>> > 
>> > >Folks,
>> > >
>> > >Yesterday we discussed the science implications of changes proposed for the ACA 
>> > >7m antenna specifications and requirements.  I tried to summarize these.
>> > >In the spaces of today's LPR and LLC discussions I spoke about these with
>> > >Tetsuo.  On the basis of our chat, I think I understand the reasons for some
>> > >of these changes.  In principle, I think it is not good to have many different
>> > >versions of antenna specifications and requirements.  But ALMA is a project of
>> > >practicalities, not principles.
>> > >
>> > >I added some further words to the discussion document at:
>> > >http://www.cv.nrao.edu/~awootten/mmaimcal/ACASpecReqsDiffs.txt
>> > >Please comment.
>> > >
>> > >Clear skies,
>> > >Al
>> > >+--------------------------------------------------------+
>> > >| Alwyn  Wootten   (http://www.cv.nrao.edu/~awootten/)	 |
>> > >| Project Scientist, Atacama Large Millimeter Array/US   |
>> > >| Astronomer, National Radio Astronomy Observatory       |        
>> > >| 520 Edgemont Road, Charlottesville, VA 22903-2475, USA |
>> > >| (434)-296-0329 voice             (434)-242-4713 cell   |
>> > >| (434)-296-0278 FAX               Help us build ALMA    |        
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>> > >  
>> > >
>> > 
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