[evlatests] EVLA System Check, 29 march

[Rick Perley]

    I used 30 minutes at the end of Dynamic Time this morning to check 
out what's working, and what isn't. 

    I did the usual things: 

    1) Fast continuum dumps (0.42 seconds) at L, C, X, and K bands to 
check for stability behavior,   (I didn't do Q, for lack of time, and 
out of general distrust of pointing.  A mistake.  See below). 
    2) Spectral line, mode '4', to check bandpasses and sensitivity, and 
P, L, C, X bands.  (I forgot to add K in, in my rush to beat the ticking 
clock). 

    Primary referenced pointing was done at C, X and K bands.  Winds 
were light. 

    Results:

    General Results:

    1) Referenced pointing worked!  So it appears that either:
             somebody fixed the flagging problems overnight, or
              the flagging of EVLA antennas (other than #14) which 
caused pointing tests to fail the last two days, is triggered by wind.  
(A hair-trigger, I would venture to say). 

    2) Other than oddities at the beginning of the L-band continuum 
observation, the performance of the EVLA antennas is very good indeed. 

    3) No phase drifts were noted at any band -- however, the scans were 
less than 2 minutes long, so the limits on temporal phase slopes are not 
small. 


    Specific Results, organized by band. 

    1) P-Band. 

    As already widely known, antennas 14, 17 and 23 are outfitted at 
P-band. 

    14 A and C gave no fringes.  14 B and D were find.  Antennas 17 and 
23 were good on all IFs. 

    2) L-Band. 

    I elected to observe simultaneous a new pair of frequencies -- 1465 
and 1835 MHz, now that we have a pair of VLA antennas that work at that 
upper frequency. 

    The first minute of the continuum (fast-dumped) data showed bizarre 
amplitudes and phases on nearly all antennas (both VLA and EVLA).  As 
this behavior did not show up on any other scan at any other frequency, 
I'm going to ignore it for now.

    The phase of 14C is oscillating back and forth by 150 degrees, on 
timescales of a few seconds.  This behavior was also seen yesterday at P 
and L bands *only*.   The oscillation is absent today also at C, X, and 
K bands. 

    Antenna 21 has no receiver. 
    Antenna 24 gave no data on any IF. 
    All other EVLA antennas worked fine.  Sensitivities are all within 
normal bounds, at both frequencies. 

    3) C-Band

    Antennas 21 and 23 have no C-band receivers. 

    Antennas 26 and 24 gave no data (and did not return pointing 
solutions either). 

    The remaining 5 antennas (13, 14, 16, 17, 18) all worked well. 
    Antenna 17 showed occasional (1 in 100) small dropouts in 
amplitude.  No phase effect noted. 
    Sensitivities for 14, 16, and 18 are the best in the array.  
Antennas 13 and 17 are like VLA antennas. 
    Tsys for 13 and 17 are too high -- particularly 17, which has Tsys 
between 65 and 110 (depending on IF).   Antenna 13 Tsys is about 60, 
explaining why its sensitivity is like the VLA norm. 

    4)  X-Band. 

    All 9 EVLA antennas are outfitted at X-band.
    Antenna 21 gave no sensible fringes.  21A and C are truly dead, B 
and D are sort-of alive (but not useful). 
    Antenna 24 gave a pointing solution, but no continuum data.  It 
returned for the line data.  I have no idea why it was missing for one 
of these three scans.

    Otherwise, all others are just fine. 

    Antenna 26 A and C have occasional amplitude drops (about 1% of the 
data), lasting a single 0.416 second integration.  The two IFs drop in 
synchronism. 

    Sensitivies of 13, 14, 16 and 26 are excellent -- better than all 
VLA antennas. 
    Sensitivities of 17 (all IFs) and 14C and D are poor.  These 
antennas have high Tsys. 

    5) K-Band. 

    Eight EVLA antennas are outfitted at K-band, and they all work just 
fine!!! 

    Antenna 26 has occasional drops, identical to those noted above for 
C and X bands. 

    Sensitivies of 14, 16, 23, and 26 are all excellent.  Antennas 13, 
17 and 18 are all about the same as average VLA. 
    Only 24 has poor sensitivity -- clearly due to the reported high 
Tsys of over 100 K.