[daip] Two curiosities from 1 Software correlator FITS file
Walter Brisken
wbrisken at nrao.edu
Wed May 7 11:37:36 EDT 2008
I have produced a FITS file
/home/swc/difx/projects/bl156b/BAD-IM.FITS
that shows two weird effects. I am not sure if the problems are with my
data or within AIPS.
FIRST ISSUE: I believe is a minor printing issue in LISTR with
OPTYP='SCAN':
-------------------------------------------------------------
LISTR1: Task LISTR (release of 31DEC08) begins
cosmos LISTR(31DEC08) 2179 07-MAY-2008 11:13:38 Page 1
File = BAD-IM .UVDATA. 3 Vol = 3 Userid = 2179
Freq = 8.102490000 GHz Ncor = 1 No. vis = 70737
Scan summary listing
.
.
.
ID Source Freq(GHz) Velocity(Km/s) Rest freq (GHz)
1 All Sources 8.1025 0.0000 8.1025
IF( 2) 8.1165 0.0000 8.1025
IF( 3) 8.1585 0.0000 8.1025
IF( 4) 8.2285 0.0000 8.1025
IF( 5) ********* 0.0000 8.1025
IF( 6) 8.4105 0.0000 8.1025
IF( 7) 8.5505 0.0000 8.1025
IF( 8) 8.5785 0.0000 8.1025
Frequency Table summary
cosmos LISTR(31DEC08) 2179 07-MAY-2008 11:13:39 Page 4
File = Y .UVDATA. 3 Vol = 3 Userid = 2179
FQID IF# Freq(GHz) BW(kHz) Ch.Sep(kHz) Sideband
1 1 8.10249000 16000.0010 2000.0001 1
2 8.11649000 16000.0010 2000.0001 1
3 8.15849000 16000.0010 2000.0001 1
4 8.22849000 16000.0010 2000.0001 1
5 8.31249000 16000.0010 2000.0001 1
6 8.41049000 16000.0010 2000.0001 1
7 8.55049000 16000.0010 2000.0001 1
8 8.57849000 16000.0010 2000.0001 1
--------------------------------------------------------------
The frequency for IF(5) is set to "stars". Given that the second table
doesn't show anything odd, I don't think there is a problem with the
actual numbers but instead think there is a printing problem. A quick
PRTAB on the FQ table shows:
--------------------------------------------------------------
PRTAB1: Task PRTAB (release of 31DEC08) begins
cosmos PRTAB(31DEC08) 2179 07-MAY-2008 11:13:24 Page 1
BAD-IM .UVDATA. 4 Disk= 3 FQ Table version 1
Title: AIPS UV DATA FILE FREQUENCY TABLE
Created by FITLD on 07-MAY-2008 10:57:07
Last written by FITLD on 07-MAY-2008 10:57:07
Ncol 5 Nrow 1 Sort cols:
Table has 1 keyword-value pairs:
NO_IF = 8
Table format incompatable with FITS ASCII tables
COL. NO. 1 2 3 4 5
ROW FRQSEL IF FREQ CH WIDTH TOTAL BANDWI
SIDEBAND
NUMBER HZ HZ HZ
1 1 0.0000000000D+00 2.000000E+06 1.600000E+07 1
1 1.4000000000D+07 2.000000E+06 1.600000E+07 1
1 5.6000000000D+07 2.000000E+06 1.600000E+07 1
1 1.2600000000D+08 2.000000E+06 1.600000E+07 1
1 2.1000000000D+08 2.000000E+06 1.600000E+07 1
1 3.0800000000D+08 2.000000E+06 1.600000E+07 1
1 4.4800000000D+08 2.000000E+06 1.600000E+07 1
1 4.7600000000D+08 2.000000E+06 1.600000E+07 1
PRTAB1: Appears to have ended successfully
PRTAB1: cosmos 31DEC08 TST: Cpu= 0.0 Real= 0
---------------------------------------------------------------
Again, nothing odd in the table. The version of AIPS I'm running here
correctly shows IF(5) for a different test FITS file with 8 IFs, so I am
suspecting that there might be a compiler or fortran library bug that is
preventing that certain number from printing properly.
SECOND ISSUE: FITLD complains that:
-----------------------------------------------------------------------
FITLD1: GETDEL: No IM entry stn 11 src 4 sub 1 FQ 1 at 0/19:08:15
FITLD1: GETDEL: No IM entry stn 11 src 4 sub 1 FQ 1 at 0/19:08:16
FITLD1: GETDEL: No IM entry stn 11 src 4 sub 1 FQ 1 at 0/19:08:17
.
.
.
FITLD1: GETDEL: No IM entry stn 11 src 4 sub 1 FQ 1 at 0/19:09:24
-----------------------------------------------------------------------
The messages only refer to one scan (the 4th one) at one antenna (11).
This is odd for a couple reasons. First, there is no visibility data for
source 4/antenna 11. The second is that antenna 11 was not in the array
for scans 1 through 4, so I would have expected warnings for scans 1
through 3 as well.
This example is of a slightly non-standard case -- I've concattenated
(outside AIPS) two software correlator passes into 1 FITS file and the
first only had 10 stations, the second had 11. I expect that this
concattenation will become a popular way to minimize the total number of
FITS files that are produced by software correlation.
What happens when no IM table is found? Are zeros just filled in? Will
this cause trouble for anything using the IM table later?
Thanks!
Walter
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