[daip] Re: Request for help on CLCOR (fwd)

[Leonia Kogan]

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>From cwalker at eolus.aoc.nrao.edu Tue Dec  3 10:54 MST 2002
Date: Tue, 3 Dec 2002 10:54:32 -0700
From: Craig Walker <cwalker at aoc.nrao.edu>
To: Mark Reid <reid at cfa.harvard.edu>
Cc: Leonia Kogan <lkogan at zia.aoc.NRAO.EDU>,
        Andreas Brunthaler <brunthal at mpifr-bonn.mpg.de>
Subject: Re: Request for help on CLCOR (fwd)
Reply-To: cwalker at cv3.cv.nrao.edu
References: <200212022222.PAA04637 at bonito.aoc.nrao.edu> <Pine.LNX.4.44.0212030939170.24816-100000 at mjr.cfa.harvard.edu>
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Mark

I suggest two tests that you could do fairly easily, I think, that
could satisfy you that Leonia has things right.  One is simply to 
correct the file that you are offering and see that the rates slow down.
That should give you the sign.  The second is to make the test that
you mention - take some data for which you have derived your delta 
atmosphere parameters and correct the data from which those derivations 
were made.  Then new corrections could be derived.  The should come 
out zero.  That makes sure everything is internally consistent.  Between
those two, I think you have what you need.

As for a correlator based test, making incremental changes that are
accountable in terms of zenith delay is probably not something that
will be productive.  The atmosphere on the correlator is not 
parameterized that way so relating a small change to the correlator
model to a zenith change will probably be as prone to error as anything
being done in CLCOR.  The easier test is to turn the atmosphere off,
as I gather it was for the data set you are offering.  Another such test
could be done, but is it needed?  It does require a special version
of the correlator software be made.

As for NRAO developing software, we have never had proper support for
the VLBA.  AIPS++ took away the main software group before the VLBA
tools in AIPS were really ready.  And AIPS++ has not delivered yet.
Items like the ability to correct the atmosphere based on some scans 
around the sky, that you are trying to do, should have been there 
from very near the beginning.  We have many other holes in our system.
Now we have a very minimal AIPS group with tremendous pressures on 
their time.  Any help that a user can provide for testing means that
other users stand a chance to get the things that they need.

Cheers,

Craig

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    R. Craig Walker            Array Operations Center
    cwalker at nrao.edu           National Radio Astronomy Observatory
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