[daip] forwarded message from Mark Reid

[Eric Greisen]

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From: Mark Reid <reid at cfa.harvard.edu>
To: egreisen at cv3.cv.nrao.edu
cc: Andreas Brunthaler <brunthal at mpifr-bonn.mpg.de>
Subject: Request for help on CLCOR
Date: Fri, 13 Sep 2002 15:37:54 -0400 (EDT)


Eric,

We are doing astrometric VLBA projects, trying to measure
the proper motions of galaxies.  This requires correcting
for small errors in the atmospheric model of the correlator.
We use multi-band delays and fringe rates on sources of known
position to solve for the error in the vertical delay through
the atmosphere for each station as a function of time.
Now, we would like to be able to input these vertical delay
errors and have CLCOR update a CL table for the resulting
phase shifts.

Currently, there are two problems with CLCOR:

  1) One must input a full atmospheric model, instead of
     small adjustments.  We have no good way to get this 
     information from the correlator residuals.

  2) One must re-run CLCOR for each antenna, one at a time.
     For 10 stations this is very clumsy.
 
So, could you change CLCOR to do what we need?

This would involve the following:

1) Reading a text file containing the following:

    Station_1       Time_1        Vertical_delay_error
    Station_1       Time_2        Vertical_delay_error
    Station_1       Time_3        Vertical_delay_error
    Station_2       Time_1        Vertical_delay_error
    Station_2       Time_2        Vertical_delay_error
      .
      .
      .

2) Interpolating the Vertical_delay_errors in time

3) For each station, calculating expected delay changes,
   essentially by scaling by sec(ZA).  (We have slightly
   better "mapping functions" and could supply them to
   you.)

4) Adding the changes to a CL table.


Thanks for considering this request.

Mark
   


- -------------------------------------------------------------
Mark J. Reid                 Phone: 617-495-7470 
Harvard-Smithsonian CfA      Fax  : 617-495-7345
60 Garden Street             Email: reid at cfa.harvard.edu
Cambridge, MA 02138, USA     Web  : cfa-www.harvard.edu/~reid                  
- -------------------------------------------------------------



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