[evlatests] Modcomp-Free Test, Friday night.

[Ken Sowinski]

On Sat, 23 Jun 2007, Rick Perley wrote:

>    A)  Pulsing Data.
>
>    At all bands and all IFs and all sources, at all times, data from
> most VLA antennas is 'pulsing'.  There are three very clear behaviors:

I had thought to blame this on loss of phase switching synchronization
for VLA antennas, but looked at the pointing data and so no sign of
loss of coherence in ten second integrations.  We must look elsewhere
to explain this.  Was it present when you did the check of Barry's
fix for the short time phase problems week before last?

>    B)  VLA antennas 'late to get started, and early to leave'.

No comment.  I am reminded of Jim Oty saying that he had to leave
early to make up for coming in late.

>    My hypothesis is that the VLA antennas are actually at the wrong
> frequency in the initial scan.  Is this possible?

It is possible.  But probable?

>    C)  VLA antennas flagged bad 10 seconds before the end of a scan.
>
>    D)  Every scan had a start time, and a single record, belonging to
> the previous scan.  In all cases, the datum was bad, but was not flagged.
>
>    E)  Referenced Pointing turns off flags?

I think there are still timing problems or at least interpretation of
time differences between the executor, idcaf and alerts that generate
flags.  Some of these may be symptoms of that.

>    The following items are of a lesser concern (I hope).
>
>    Antennas 6 and 8 gave no useable data at any band -- but were not
> flagged.  Could be delays, but the error will have to be really large!

I believe these are uncorrected large delay errors.

>    Antenna 13 only worked well in IF A.  13B was dead, 13 C was weak,
> and 13D was very, very weak.  None of these were flagged at any band.

13 has some DTS system problems with both B and D.  Jim and Rob are
aware of it.

>    Antenna 5 was dead at K and Q bands -- and not flagged.  Delays?
> Pointing?

Antenna 5 does have a large pointing error.  The beam is distorted
enough that the pointing solution may have been suppressed when
referenced pointing was applied.  The results of the Wednesday night
pointing run have not yet been applied in order to leave enough errors
in to verify that referenced pointing really works.

> *************************************************************************
>    Conclusion:
>
>    We've got a lot of work to do before we're ready to turn off the
> Modcomps.

To paraphrase the Carnegie Hall joke, testing, testing, testing.