[evlatests] ACU tests -- sky survey mode

[Bryan Butler]

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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