[evlatests] Referenced Pointing Tests

[Bryan Butler]

i've always thought the median is the simplest good filter - i suspect 
we'll find no better.  should i ask keith to implement that for testing?

	-bryan


Claire Chandler wrote, On 11/18/10 13:41 PM:
> The trouble is that telcal might be able to get a solution but it might be
> rubbish.  I was thinking we should perhaps use the median of all subbands,
> but there's clearly some work to be done to establish what algorithm is
> best.
>
> Claire
>
> On Thu, 18 Nov 2010, Barry Clark wrote:
>
>> 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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