[evlatests] Referenced Pointing Tests

[Barry Clark]

How about letting telcal try another subband if it can't get a solution
on its first choice?

Bryan Butler wrote:
> yes, all the solutions are written into the pointing file.  i don't know 
> that we will ever have a truly robust way of avoiding RFI, other than 
> trying to avoid where we know it exists.  we had been thinking at one 
> point of at least allowing the user to specify which subband was used - 
> if we do that is it enough?  maybe.  certainly somebody should look into 
> whether trying to take the results from all the subbands is better than 
> one, but maybe we should just go ahead now and change the recommendation 
> for RSRO/ECSO observers so that they can use the same setup for 
> reference pointing as for observing.  i suspect that the problems 
> encountered from that will be less than the problems that arise from 
> changing configurations, but maybe i'm missing something.
> 
> 	-bryan
> 
> 
> Claire Chandler wrote, On 11/18/10 12:18 PM:
>> Hi Rick,
>>
>> You need to define what you mean by "works for wideband".  Recall that at
>> present the default algorithm in TelCal is to take the second subband from
>> the bottom of each baseband for the solution that is fed back to the
>> online system.  Therefore it relies on that subband being RFI-free.  I
>> believe that solutions are being written for all subbands for testing
>> purposes at the moment, and what we really need to do is to establish how
>> to combine the results from all those subbands to obtain a solution that
>> is not affected by RFI, and can potentially be used to enable pointing on
>> weaker sources.
>>
>> Claire
>>
>> On Thu, 18 Nov 2010, Rick Perley wrote:
>>
>>>     I ran a test of referenced pointing this morning.    There were two
>>> goals:
>>>
>>>     1) Does 'wide-band' referenced pointing work as well and reliably as
>>> 'narrow-band'?
>>>
>>>     2) Does a 15-second cadence work as well as 20-second?
>>> (Explanation:  In the past, the system used 10 seconds to move from one
>>> position to the other, and 10 seconds to integrate.  But from holography
>>> we know that the move-and-settle time is less than 5 seconds, so a
>>> 15-second (5+10) regimen should work).
>>>
>>>     To test these, I used 3C147 (~5 Jy) to measure pointing offsets at
>>> X-band, with four combinations:
>>>
>>>     1) Narrow-band with 20 seconds.
>>>     2) Narrow-band with 15 seconds.
>>>     3) Wide-band with 20 seconds
>>>     4) Wide-band with 15 seconds.
>>>
>>>     The intention was to observe each mode sufficiently long for 3
>>> consecutive pointing solutions.  Due to a blunder on my part, the 'fast'
>>> tests were observed long enough for only 2 solutions.  But that is still
>>> sufficient for the following conclusions:
>>>
>>>     A) Wide-band mode works as well as narrow-band.
>>>
>>>     B) Fast mode appears to be as good as 'slow'.
>>>
>>>     There were a few failed solutions for all four trials -- the
>>> statistics are not good enough to claim that any one of these four is
>>> better or worse than the others.  Comparison of the actual solutions has
>>> been done for only one antenna (so far) -- there is no significant
>>> differences, other than an expected change in elevation offset as the
>>> sun rose.
>>>
>>>     By looking at the detailed log, the sequence of operations is easily
>>> discerned.  (Ken claims this may be unreliable, and he intends to peer
>>> deeper after lunch).  But, be this as it may, I deduce that the
>>> *absolute minimum* time needed for a single referenced pointing
>>> measurement is (presuming the antennas are on source) is:
>>>
>>>     124 seconds for 'slow' mode,
>>>     94 seconds for 'fast'.
>>>
>>>
>>>
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