[daip] Scan listing problems

[Matt Lykins]

To the AIPS group,

I am a graduate student working on data from VLA projects AT113, AR291 and
AR320.  These are HI spectral line data towards W3, with the intent to study
the HI Zeeman effect.

I have encountered an anomaly in running FILLM, I would appreciate any
insights you can provide.  Of course, I realize that resources are limited
to answer such user questions.

BACKGROUND

* Successive scans were taken with the telescope front end transfer switches
either in normal positions (designated qual 1) or in crossed positions
(designated qual 2).  Naturally, the qual 1 and the qual 2 data must be
separately calibrated.
* Phase cal scans for each qual were taken both above and below the HI line
frequency in order to avoid the effects of the HI line.  So a given phase
cal sequence consists of 4 scans (2 quals and 2 frequencies).

PROBLEM 1 - FILLM

Normally, I run FILLM twice for each day's data, once for qual 1 and once
for qual 2.  Then I run LISTR to list the scans that have been found in each
case.  However, I can also run FILLM for quals 1 & 2 together and run LISTR
to list all scans in the data set.

* Attached file Q1.pdf is the LISTR output for qual 1 alone.  File Q2.pdf is
the LISTR output for qual 2 alone.  File Q1Q2.pdf is LISTR output for quals
1 & 2 filled together.  All three attached files are for the AT113 project
observed on 13 to 14-JAN-91.

* I would expect the number of files in Q1Q2 to equal the number of files in
Q1 plus Q2.  Instead, Q1 contains two unexpected scans because scan 49 of
Q1Q2 has been divided up into three scans in Q1, namely, scans 26-28.  Also,
the beginning of the Timerange for a scan in Q2 is often different from the
beginning of the Timerange for the same scan in Q1Q2.  An example is scan 25
in Q2 (beginning 04:47:30), compared to its equivalent scan 52 in Q1Q2.

Are these discrepancies worrisome?

PROBLEM 2 - UVCOP

After copying a multi-source uv data set from one AIPS disk to another with
UVCOP, the number of scans listed by LISTR is different.  Attached file
Q1_afterUVCOP.pdf shows this listing after UVCOP.  It is to be compared with
file Q1 (i.e. the listing before UVCOP).  Scan 7 in Q1_afterUVCOP is
actually a combination of scans 7 and 8 in Q1.  Similarly for scans 10 and
13 in Q1_afterUVCOP, each appears to be a combination of two scans in the Q1
file before UVCOP.

It appears that no visibilities have been lost.  But is are discrepancies
worrisome?

PROBLEM 3 - VLA ARCHIVE OBSERVATIONS SUMMARY TABLE

The VLA Archive Observations Summary Table for project AT113 shows a nearly
one hour time gap from 91-Jan-14 03:35:00 to 91-Jan-14 04:30:39.  Yet the
LISTR listing for the filled data show that observations took place during
this time period.  Again, is this discrepancy worrisome?

Many thanks for any information you can provide.

Sincerely,

Matt Lykins
Physics & Astronomy Department
University of Kentucky
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