[evlatests] EVLA status: AIPS weights at CXK bands on July 3

[mrupen at nrao.edu]

S7810  3jul06  04:27-08:30 IAT
------------------------------
mpr  6jul06

Report of data quality (as measured by AIPS weights)

EVLA ant. 13,14,16,18 included

Standard continuum, C X K bands
Ref.Ptg. at K band
3.3s averaging

Here I introduce two ways of looking at the AIPS weights:
by median ranking, and by median fractional weight.
- The ranking shows where the antenna falls with respect to
  the VLA antennas:
     1 means it's the best antenna in the array
    26 means it's the worst.
- The fractional weight gives a quantitative indication of
  how good or bad it is.
    0.1 means its weight is 10 times worse than the average
      antenna in the array;
    10.0 means its weight is 10 times better. 

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AIPS weights: median ranking, out of a nominal
  26 antennas
  --> 1 is the best; 26 is the worst <--

          6cm   4cm   1.3cm
  13-A    n.f.  14    ----
  13-C   ----   15    ----
  13-B    3     12    ----
  13-D    5     16    ----

  14-A    3     12    26
  14-C    4     23    26
  14-B    1     19    26
  14-D    2     16    26

  16-A    8      5    16
  16-C   16      6    17
  16-B    2      5    19.5
  16-D    6     21    25

  18-A   ----   20    ----
  18-C   ----   24    ----
  18-B   ----   23    ----
  18-D   ----   21    ----

  ---- ==> no data
  n.f. ==> no fringes (low amp, random phase)

-------------------------------------------------------------

AIPS weights: median fractional weight
  mean weight is calculated for each record
  fractional weight is the weight for the EVLA antenna,
    divided by that mean
  the median fractional weight is the median value of the
    fractional weights, derived from the distribution across
    all records in which the antenna was present
  --> high is good <---
  --> the average VLA antenna is 1.0 <--
  --> 0.1 is 10 times worse than the average;
     10.0 is 10 times better <--

          6cm   4cm   1.3cm
  13-A    n.f.  0.97  ----
  13-C   ----   0.92  ----
  13-B   1.38   1.05  ----
  13-D   1.16   0.91  ----

  14-A   1.32   0.96  0.08
  14-C   1.18   0.81  0.09
  14-B   1.41   0.87  0.09
  14-D   1.32   0.91  0.09

  16-A   1.17   1.13  0.93
  16-C   0.95   1.15  0.92
  16-B   1.41   1.12  0.82
  16-D   1.15   0.85  0.34

  18-A   ----   0.84  ----
  18-C   ----   0.75  ----
  18-B   ----   0.77  ----
  18-D   ----   0.84  ----

  ---- ==> no data
  n.f. ==> no fringes (low amp, random phase)

-------------------------------------------------------------

MISC.:

6cm: 
  ant. 16 occasional dropouts (?)

4cm:
  ant. 13:
    dropouts (?) simultaneous in all IFs, but only on 1331+305/1407+284
      ...dominate amp.diff. in TVFLG
  ant. 18:
    dropouts in IF 2 dominate amp.diff. in TVFLG

1.3cm:
  ant. 14:
    - IF B missing for 2nd part of run
    - MUCH noisier than all other antennas

-------------------------------------------------------------

BOTTOM LINE:
  no useful data from
    ant. 13 6cm IF AC ; 1.3cm all IFs
    ant. 18 6cm all IFs; 1.3cm all IFs

  6cm mostly very good (weights place antennas in top 5 for most IFs),
    - exception is ant. 16, IF C, which is only average

  4cm roughly average compared to other antennas
    ant. 14 IF C is quite bad (near the bottom)
    ant. 16 IFs ABC are quite good (in the top 5)
    ant. 18 is quite bad (near the bottom)

  1.3cm pretty awful (presumably due to pointing?)
    ant. 14 by far the worst in the array
    ant. 16 below average
            next-to-worst in IF D

  Seem to see dropouts (low amp. records on calibrators, with fine phases)
    ant. 18, 4cm, IFs BD
    ant. 13, 4cm, all IFs, but only on strongest sources (--> low fractional
      change)
    possibly ant. 16 at 6cm

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