[evlatests] Dec. 20 Stress Test results

[Emmanuel Momjian]

Day of observation: 61175
Observation time-range: 03:05:50 to 03:58:49 LST
Observe file located at: www.aoc.nrao.edu/~emomjian/observe/Stress19Dec.obs
Operator's log located at: www.aoc.nrao.edu/~emomjian/observe/2007-12-20_0418_AMEVLA.txt


The run includes both continuum (dump time 0.4 s) and spectral-line (dump time 3 s) scans.

Please note that I didn't report anything on Antenna 1, as it still needs more work (per Ken's email).



Results:

General:

    -Global VLA-EVLA phase jumps are seen in all bands after the P-band 
scans.

    -Short shallow drops seen in various EVLA antennas and bands.

    -First (bad) record: The first (bad) record of each scan that 
follows a band change is seen in the UV data (the data were loaded with 
on-line flagging applied (FILLM cparm=0 2048 0)). Examples:

X-band scan ends at 0/04:27:20 IAT (this is the time stamp of the last 
record of this scan), and a K-band scan follows and shows (extracted 
from LISTR for demo purposes):

Baselines      1 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 210 211
   0/04:27:21   69  77      31  50  38  25   6  16  50   (1000 =   1.000 
Jy)
   0/04:27:32      453     419     463 467 433 476       (1000 =  10.000 
Jy)  
   0/04:27:33      440     419     454 474 436 478
   0/04:27:33      443     413     452 464 430 484
   0/04:27:34      438     417     459 473 438 479

This behavior is seen in all continuum scans that follow continuum scans 
from other bands.

Moreover, a similar bad record exists in the very first scan of the run, 
which was in X-band. A bad record shows up in the uv data at 0/04:18:48 
IAT, while the stream of good data starts after a few minutes at 
0/04:22:57 IAT (after the antennas got on source).

    -VLA 7: C, X and K bands: IF A only shows short shallow drops in 
amplitude in the time range that spans between 0/04:41:30 and 0/04:48:00 
IAT, during which there were scans in C, X, and K bands. No other scans 
in these bands or in other bands show this behavior. the following plot 
is an example of this as seen in C-band:
www.aoc.nrao.edu/~emomjian/observe/VLA7_CBAND_AMP_20071220.ps

    -EVLA 26 in L, C, X, K, and Q bands, all IFs: phased are jumping up 
and down among multiple states. At the instances of the phase jumps, the 
correlator coefficient is recording a short drop. When the phases 
stabilize in a given state, the amplitude values stay at the optimal 
level. Examples of this phase behavior can be seen in the following two 
plots:
X-band: www.aoc.nrao.edu/~emomjian/observe/EVLA26_XBAND_PHASE_20071220.ps
C-band: www.aoc.nrao.edu/~emomjian/observe/EVLA26_CBAND_PHASE_20071220.ps

Band Specific:

X-band:

    -EVLA 14: IFs C & D (i.e. pol L), have lower correlation 
coefficients than IFs A & B by a factor of 1.5. This seems to be due to 
the higher Tsys values seen in IFs C & D, which are around 70 K, 
compared to the 32 K values seen in IFs A & B.
 


K-band:

    -VLA 27: IFs A & B (i.e. pol R), have lower correlation coefficients 
than IFs C & D by a factor of 3. This seems to be due to the higher Tsys 
values seen in IFs C & D, which are around 350-400 K, compared to the 
35-40 K values seen in IFs A & B.

    -The following show similar symptoms, hence they are grouped together:
    1)EVLA 13: IF C (in all three scans) starts on time with other IFs 
but with lower correlator coefficients (factor of 3 lower), however 
after about 4 seconds it begins recording good correlator coefficient 
values.
    2)EVLA 16: IF A (in 1st and 3rd scans) starts on time with other IFs 
but with lower correlator coefficients (factor of 4 lower), however 
after about 4 seconds it begins recording good correlator coefficient 
values.
    3)EVLA 18: IFs A & C (in all three scans) start on time with other 
IFs but with lower correlator coefficients (factors of 4-6 lower), 
however after about 4 seconds it begins recording good correlator 
coefficient values.
    4)EVLA 25: IFs A & C (in the first two scans) start on time with 
other IFs but with lower correlator coefficients (factors of 1.1-1.3 
lower), however after about 4 seconds it begins recording good 
correlator coefficient values.

    -EVLA 19 and 25: all IFs have lower correlator coefficient values 
compared to other VLA or EVLA antennas by factors of about 2 and 4, 
respectively. Tsys values for these two antennas are about 130 and 300 
K, respectively, while a typical value seen in other VLA or EVLA 
antennas is about 40-50 K.
   


L-band:
    -VLA 6: All IFs show short shallow drops in amplitude.

    -VLA 7: Bad data at the end of an L-band continuum scan between IAT 
0/04:54:38 and 0/04:55:00. During this 22 second interval, the Tsys 
becomes unstable and starts changing between different values ranging 
between 6 and 32 K. The Tsys value before this was constant and at 
around 15-17 K, depending on the IF, which by itself seems to be lower 
than Tsys values seen in other antennas.

    -VLA 28: all IFs, a big jump is correlator coefficient values is 
seen starting at 0/04:38:01 IAT untill 0/04:39:20 IAT (this is one full 
scan). During this jump, the correlator coefficient values become lower 
by a factor of 18. The Tsys during this scan is very unstable with 
values as high as 21000 K.

    -ALL EVLA antennas: IFs A & C in the last L-band scan (0/04:57:47 - 
0/04:59:00 IAT) have very low correlator coefficient values. In IF C, 
the values are lower by at least a factor of 40, while IF B has values 
lower by a factor of about 200.  The phases are completely unstable. The 
Tsys doesn't show any odd behavior during this time range.



P-band: (percentages below are given with respect to optimal values seen 
in most other antennas).

    -EVLA 11: fringes are at 65% in IFs A & B, at 75% in IF C, and about 
90% in IF D.
    -EVLA 13: no fringes in IFs A & C. Very weak or no fringes in IFs B & D.
    -EVLA 14: fringes are at 75% in IFs A & C. Other IFs are ok.
    -EVLA 18: fringes are at 50% in IF C. Other IFs look ok.
    -EVLA 19: fringes are at 75% in IF D. Other IFs look ok.
    -EVLA 21: fringes are at 80% in IF C. Other IFs look ok.
    -EVLA 23: fringes are at 85% and 65 % in IF A & C, respectively. IFs 
B & D look ok.
    -EVLA 25: weak fringes (10% or less) in IF B. Other IFs look ok.
    -EVLA 26: weak or no fringes in all IFs.