[evlatests] Multiple System Failures

[Rick Perley]

    I have checked the 'failure modes' for the subsequent Mars 
observation at X-band, and find a different pattern than seen at C-band 
(which followed X):

    Failure mode 'A' on subbands 1, 2, 3, 4, 8, 9, 10 and 12 (AIPS 
notation, subtract 1 for widar)
    Failure mode 'B' on subbands 14 and 15
    All data present on subbands 5, 6, 7, 11, 13 and 16. 

    So, provided the failure pattern did not change between the 
referenced pointing observation and the subsequent Mars observation (and 
I suppose it shouldn't, as the correlation configuration was the same), 
then subbands 1 and 2, from which the referenced pointing solutions are 
made, had half the antennas providing pure zeros on almost all the 
baselines, which is perhaps enough to cause it to fail for all antennas?

    Rick

Ken Sowinski wrote:
> On Mon, 2 Jan 2012, Rick Perley wrote:
>
>>    2) Referenced pointing failed twice -- on 3C138 and on J1118+1234 --
>> the source I use for Mars.  The first failure is easy to explain -- the
>> antennas were busy unwrapping, so of course we were not on the source.
>> (A added curiosity here however -- bdf2aips filled the pointing data
>> even though we weren't on source.  For the four successful pointing
>> determinations, bdf2aips did not fill the data.  Apparently, it is
>> sensitive to whether the antennas are actually on source or not.)
>>    The second failure is more worrisome.    The Mars observation also
>> required a modest slew -- about three minutes from 3C138 (which, it
>> should be noted, the antennas never reached before the allotted time was
>> up).  Yet I am confident we reached Mars before the pointing solution
>> started, since I have 65 seconds of unflagged data on Mars at L-band.
>> (Note, however, that at L-band, there is not enough flux to actually
>> know if we're on the source -- I have to trust the antenna flags to
>> justify the statement made above).  Now, the time spent on Mars at
>> L-band was far too long -- I requested 15 seconds of 'on source', but
>> got more than 65.  There was then a gap of the appropriate length for an
>> X-band pointing determination, after which the normal sequence of
>> observations began again.
>
> There were no poinitng solutions for J1118+1234 because antsol
> did not converge (or had no data) for subbands 0 and 1
> (Widar notation) and subband 1 is the default subband used by
> the pointing solver.  Now, why antsol was not happy is the next
> question; perhaps it is related to the problems Rick reported
> in the third part of his report.