[daip] VLBA + Arecibo cal transfer

[Shami Chatterjee]

Hi Joan,

This is an aips question, but since it involves ANTAB, I thought you might 
be able to comment on it as well. Briefly: I'm reducing data for a VLBA + 
Arecibo experiment. (And it's good data, according to POSSM etc!) VLBA 
came with cal transfer, which I have mergecal'ed to TY 2, GC 2. For 
Arecibo, Tapasi sent me a file with SEFD values for my run, with the 
following note:

# These are actually SEFD values. With Gain=1, these could be used
# as Tsys for VLBI calibration. As Arecibo Telescope's gain is both
# Az and Za dependent, and AIPS can not handle such function, we
# have decided to provide the users with SEFD values. 
# Shami, for your Expt. these numbers have been derived from
# the continuum record at 1405 MHz, two pols. have been
# averaged. I think, you can use it in ANTAB to creat
# a Tsys table.
Gain = 1
Tsys /
109  7:10:20.00      3.66561
109  7:10:30.00      3.66012
<etc>

Looking at the VLBA TY values, I have:
----
ROW   TIME         TIME INTER   SOURCE ID   ANTENNA    SUBARRAY   FREQ ID
1     07:05:11.0   00:01:39.0       5           2          1         1
2     07:07:34.0   00:00:53.0       1           2          1         1
...
84    09:27:49.5   00:01:00.0       3           2          1         1
----
for each antenna.

Following notes from Emmanuel Momjian, Tapasi and mostly from
"EXPLAIN ANTAB", I created a fake header and Tsys input table:
----
CONTROL INDEX = 'R1', 'L1', 'R2', 'L2', 'R3', 'L3', 'R4', 'L4' /
!
GAIN AR ALTAZ DPFU = 1.0 POLY = 1.0 / 
! (Flat gain curve for AR, all IF's and polarizations,
! zenith point source sensitivity of 1 K/Jy)
!
TSYS AR FT=1.0 INDEX = 'R1', 'L1', 'R2', 'L2', 'R3', 'L3', 'R4', 'L4' /
!
109  7:10:20.00  3.665610 3.665610 3.665610 3.665610 3.665610 3.665610 
3.665610 3.665610
109  7:10:30.00  3.660120 3.660120 3.660120 3.660120 3.660120 3.660120 
3.660120 3.660120
<etc> - one entry every 10 seconds, till
109  9:20:50.00  3.407700 3.407700 3.407700 3.407700 3.407700 3.407700 
3.407700 3.407700
----
where I just repeated the SEFD value Tapasi sent me 8 times, once for each 
IF and poln, as I specify in the CONTROL card.

Now I load it:
mingus> ANTAB1: Task ANTAB  (release of 31DEC02) begins
mingus> ANTAB1: ZTXOP2: using translated file name = [...]
mingus> ANTAB1: Gain curve read for station: AR
mingus> ANTAB1:      0 unidentified records skipped on input
mingus> ANTAB1: Appears to have ended successfully

Setting prtlev 1 echoes the full input table, so no format problems.

But when I use PRTAB, there is no new information in the table. If I send
it to a new TY table, it gets created, but is empty:

mingus> SNPLT1: Task SNPLT  (release of 31DEC02) begins
mingus> SNPLT1: ERROR: SELECTED TABLE IS EMPTY

I can see several potential problems, in order of likelihood:
1) I made a mistake in the header.
   (I've tried it with and without the CONTROL card: no difference)
2) The timestamps (every 10 seconds) do not match the exact scan times 
aips wants in the table. (How can that be?)
3) Some confusion regarding the day number.
4) ...?

Is there an obvious problem, and how do I fix it?
My apologies for the bother, and many thanks for your help!
Shami

-- 
 Shami Chatterjee    
 http://www.astro.cornell.edu/~shami/ 
 Preudhomme's Law of Window Cleaning: It's on the other side.