[daip] APCAL not working properly.

[R. Craig Walker]

With this message, I will describe my problem.  If further debugging is
needed, I'll try to reproduce it at the AOC (I'm working on a Mac at home
using a recently upgraded 31DEC15 AIPS).

I am calibrating 20cm VLBA data taken with the PFB (8 dual pol channels)
in February 2015 and correlated last week.

The GC table appears to be fine.  There are reasonable K/Jy values for all
IFs.  The gain curve has 1.0 for the first element, INDE for the rest. 
X_val and Y_val are INDE (I'm not sure what they are).

The original TY table seems structured ok, but had a moderate number of
spurious values and quite a bit of noise.  I ran TYSMO twice, first to
clip with long windows, then to smooth with a shorter window.  The
resulting TY table 3 looks good in all channels.

I then run APCAL (inputs below).  The resulting gains are in the range of
15-20 for IFs 1 and 6 (both polarizations) and around 0.3 for IFs
2,3,4,5,7,8.  Not good!  I ran APCAL without opacity corrections as you
can see in the inputs.

Any idea why two IF channels seem to get proper calibration while the rest
get something way too small?

A secondary issue, what I really want is to specify TAO0 and have it use
that for the opacity without trying to compare Tsys with physical
temperatures.  This is because I think the Tsys variations are due to RFI
(L band) rather than the troposphere.  It is not clear from the
HELP/EXPLAIN file that this is possible (or at least I'm not seeing it). 
A quick look in the code was also not illuminating.  Is what I want to do
possible?  If not, can it be made so?

Now the APCAL inputs:

>inp
AIPS 1: APCAL     Task to generate an amplitude calibration SN table
AIPS 1: Adverbs     Values                 Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME     'MAIN_49A8'             Input UV file name (name)
AIPS 1: INCLASS    'MULTI'                 Input UV file name (class)
AIPS 1: INSEQ         1                    Input UV file name (seq. #)
AIPS 1: INDISK        5                    Input UV file disk unit #
AIPS 1:
AIPS 1: ANTENNAS   *all 0                  Antennas to calibrate
AIPS 1: SUBARRAY      0                    Subarray 0 -> all
AIPS 1: STOKES     ' '                     Stokes type ('R','L',' ')
AIPS 1: BIF           0                    Start IF number
AIPS 1: EIF           0                    End IF number
AIPS 1: FREQID       -1                    Freq. ID to calibrate
AIPS 1: SOURCES    *all ' '                Sources to calibrate
AIPS 1: TIMERANG   *all 0                  Time range to calibrate
AIPS 1:
AIPS 1: TYVER         3                    TY table version number.
AIPS 1: GCVER         1                    GC table version number.
AIPS 1: SNVER         0                    Output SN table version.
AIPS 1:                                      0 -> highest unique
AIPS 1: OPCODE     ' '                     Opacity correction opcode:
AIPS 1:                                    '    ' -> no opacity corr.
AIPS 1:                                    'GRID','GRDR','OPAC','OPCR',
AIPS 1:                                      'LESQ' -> fit for opacity
AIPS 1: APARM      *all 0                  Calibration parameters:
AIPS 1:                                    (1) -> B factor (def. 1.0)
AIPS 1:                                    Opacity parameters:
AIPS 1:                                    (2) -> ZA limit (deg)
AIPS 1:                                    (3) >=0  use spillover
AIPS 1:                                             correction
AIPS 1:                                    (4) > 0  use all FQ in
AIPS 1:                                             opac. soln.
AIPS 1:                                    (5) Limit to sec(z) plotted
AIPS 1:                                    (6) > 0 => normalize Tsys
AIPS 1:                                        by average Tsys
AIPS 1:                                    (7) Use IF AP(7) for
AIPS 1:                                        normalization instead
AIPS 1: SOLINT        0                    Solution interval (min)
AIPS 1:                                       0 -> use all data
AIPS 1: INVERS        1                    WX table version number.
AIPS 1:                                       0 -> use text file
AIPS 1: CALIN      *all ' '                Text file with weather info.
AIPS 1:                                       Must be ' ' if using WX
AIPS 1:                                       table (INVERS).
AIPS 1: TRECVR     *all 0                    Receiver temperatures (K);
AIPS 1:                                       in (R,L) pairs.
AIPS 1: TAU0       *all 0                  Zenith opacities (per ant.)
AIPS 1: DOFIT        -1          -1        Fit type (per ant.)
AIPS 1:              -1          -1          -1 -> no opacity correction
AIPS 1:              -1          -1           0 -> apply TRECVR only
AIPS 1:              -1          -1           1 -> solve for Trec using
AIPS 1:              -1          -1                fitting method spec.
AIPS 1:              -1          -1                in OPCODE; then apply
AIPS 1:              -1          -1          -1          -1
AIPS 1:              -1          -1          -1          -1
AIPS 1:              -1          -1          -1          -1
AIPS 1:              -1          -1          -1          -1
AIPS 1:              -1          -1
AIPS 1: PRTLEV        0                    Print level
AIPS 1: DOTV         -1                    TV selection (<0 -> PL file)
AIPS 1: LTYPE         3                    Plot labeling
AIPS 1: GRCHAN        0                    TV Graphics channel to use

Cheers,

Craig


---------------------------------------------------------------------
    R. Craig Walker            Array Operations Center
    cwalker at nrao.edu           National Radio Astronomy Observatory
    Phone  575 835 7247        P. O. Box O
    Fax    575 835 7027        Socorro NM 87801   USA
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