[evlatests] ACU tests -- sky survey mode

[Bryan Butler]

that makes no sense, in light of the testing we've done before.  i'll 
look at the script.  i suspect some misunderstanding in how you set it 
up in the OPT, since this is the first time you've done it.

	-bryan


Rick Perley wrote, On 12/23/14 12:36 :
>      You're misreading what I wrote.
>
>      By 'overshoot', I mean that (for example) ea18 travelled six times
> too far.  That is -- instead of traversing 2 degrees, it traversed 12.
> Each antenna had a different 'overshoot' -- given apparently by its
> fringe rate.
>
>      The cut profiles make this abundantly clear.
>
>      It's not even clear that the 'speedy' antennas travelled in the
> right ascension line that was requested.  The 'slow' antenna show the
> expected sidelobe about -13 dB from the peak.  The 'fast' antennas show
> much lower sidelobes -- and many more of them.
>
>      Rick
>
> On 12/23/2014 12:32 PM, Bryan Butler wrote:
>>
>> the "overshoot" is expected.  an OTF "line" backs up by 1 phase center
>> from the first location for its real start position, in order to be up
>> to speed by the time it hits that first phase center.  this backed-up
>> portion is marked with a different scan intent, which you're probably
>> not picking up and flagging on.  at the end, this is almost certainly
>> just the expected overshoot from the antenna motion.  i assume by
>> "nearly six" you mean six integrations, which is 0.6 seconds.
>>
>> for the rest, i defer to steve & barry.  there's nothing
>> antenna-dependent in the python function portion of this - i can't
>> vouch for the executor portion.
>>
>>     -bryan
>>
>>
>> Rick Perley wrote, On 12/23/14 12:10 :
>>>      I've been asked to continue testing of the new ACU-equipped
>>> antennas, using the new 'sky survey' modes.  These allow one to speed
>>> through a specified part of the sky at different rates.
>>>
>>>      An initial test was run yesterday.  For this initial test, I picked
>>> two positions:  the first one (true) degree east of 3C48, the other one
>>> degree west of 3C48.    Six 'cuts' were specified, each traversing the
>>> two degree separation.   The idea was to get a nice cut through the
>>> primary beam, roughly from the 2nd null on one side to the second null
>>> on the other.  They specified cuts were:
>>>
>>>      1) West side to East side in 4 minutes.  This is twice the
>>> 'sidereal' rate.
>>>      2) East side to West side in 4 minutes.         ditto
>>>      3) West side to East side in 2 minutes.   This is 4X sidereal
>>>      4) East side to West side in 2 minutes.           ditto
>>>      5) West side to East side in 1 minute.    This is 8X sidereal
>>>      6) East side to west side in 1 minute.             ditto
>>>
>>>      Averaging time was set to 0.1 seconds.  For each of these six cuts,
>>> I specified 100 phase steps.  So, for the first two cuts, the number of
>>> integrations per phase step was 24.  For the next two, 12, and for the
>>> last two, 6 integrations/step.
>>>
>>>      The results were *completely* different than expected.
>>>
>>>      Each antenna moved at a different rate!  The only antennas which
>>> traveled at close to the specified rates were ea04, 06, 15, 17, 20, 22,
>>> and 28.  Some antennas zipped through the pattern at many, many times
>>> the specified rate.  The most extreme example was ea18, which went
>>> through the pattern at about six times the specified rate. This
>>> 'amplification' factor was the same for all five completed cuts.  (For
>>> reasons unknown, the last cut was not executed).
>>>
>>>      Furthermore, the profiles show that only the 'slow' antennas with
>>> smooth motion. The faster the cut, the more jagged the profile. The
>>> fastest ones are actually in big steps -- looking rather like holography
>>> mode!
>>>
>>>      It's easy to find the basic relation -- the antenna motion
>>> amplification is a factor of the fringe rate!  The target source was
>>> rising over the west arm -- elevation = 50 degrees, at which point the
>>> motion is almost entirely in elevation.  Fringe rates are high for the
>>> west arm, and low for the others.  All the 'fast' antennas were on the
>>> west arm -- the further out the arm, the faster the antenna moved (and
>>> the more steplike).  All the 'slow' antennas were near the center of the
>>> array, on the E and N arms.
>>>      Examination of the cuts show that the antennas did not start and
>>> stop at the specified points, but overshot -- on both ends by a factor
>>> of up to  nearly six.
>>>
>>>      So something is clearly not right here.  I don't think I did any
>>> illegal in the setup (the OPT is really simple for this mode). But
>>> clearly it's not working in any sensible manner.
>>>
>>>
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