[daip] CLCOR SU table update problem (?)

[Leonia Kogan]

Hi Craig,

I am sending you the copy of the message I sent to Lincoln recentely. 
As you see I have a small difference between JPRECS(AIPS) and SCHED's
results. The difference is under 0.25mas for the data I selected for the 
test.

Lincoln reproduced the coordinate calculation using his own program 
and got the difference with JPRECS/SCHED about 20 mas.

I asked John Benson to repeat the calculation using CALC.
But as I understand it is not simple to do it, because CALC does not 
carry out the direct recalculation of the coordinates and John needs 
to design a special tool to carry out the recalculation.
I am affraid that an additional mistake can be added at the tool creation.

So may I ask you to say something about the SCHED(STAR LINK) accuracy 
from your point of veiw?

Thank you

Leonia 
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>From daip-admin at donar.cv.nrao.edu Wed Oct 10 14:57 MDT 2001
From: Leonia Kogan <lkogan at aoc.nrao.edu>
To: lincoln at play.harvard.edu, daip at cv3.cv.nrao.edu
Subject: Re: [daip] CLCOR  SU table update  problem (?)
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Date: Wed, 10 Oct 2001 14:56:16 -0600 (MDT)
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Hi Lincoln,

I have carried out a test comparing the JPRECS' and SCHED's accuracy.

I took the summary file be024.sum of the experiment be024, which gives me both 
the epoch (J2000) and the observation time coordinates.

You may know that recentely I fixed several bugs inside of JPRECS.  I
used the Eric's task TSPOS to compare initial (input) J2000 coordinates
with the observation time coordinates and recalculated back to the
J2000 coordinates. Inside of the TSPOS I added the APARM(9) to the JD
to have the SCHED time. The time was '20010704', 20:54:45

The following table gives the result of TSPOS and SCHED:

TSPOS1: Task TSPOS  (release of 31DEC01) begins
         Init. J2000 RA  Init J2000 DEC   The time RA      The time DEC
TSPOS1:  14:28:32.6600   42:40:20.6000   14:28:36.110939  42:40:16.270258

         Recalc back RA  Recalc back DEC  The difference Init-Recalc J2000, mas
TSPOS1:  14:28:32.6600   42:40:20.6000         0.0000         0.0000
 SCHED:
         Init. J2000 RA  Init J2000 DEC   The time RA      The time DEC
         14:28:32.6600   42:40:20.6000   14:28:36.110948  42:40:16.27049

This table shows:

1. Recalculation back to J2000 does not have a mistake more than E-4mas.

2. Difference between JPRECS and SCHED is:
   deltaRA  = E-5sec= 0.15mas
   deltaDEC = 0.24mas

Leonia                

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>From daip-admin at donar.cv.nrao.edu Wed Oct 10 08:36 MDT 2001
From: Lincoln Greenhill <lincoln at play.harvard.edu>
To: Leonia Kogan <lkogan at zia.aoc.NRAO.EDU>
cc: daip at cv3.cv.nrao.edu
Subject: Re: [daip] CLCOR  SU table update  problem (?)
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Date: Wed, 10 Oct 2001 10:35:21 -0400 (EDT)
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Status: RO



Hi Leonia,

In FITLD, JPRECS is run w/o GR.  
Perhaps this code, which is part
of an if-then is not called?

I am concerned about the 5 mas discrepancy
between my precession/nutation code and AIPS' code.
Perhaps I jumped to conclusions as to what might be
responsible for the discrepancy.

How accurate is JPREC supposed to be?


Regards,

Lincoln


Lincoln J. Greenhill      Harvard-Smithsonian Center for Astrophysics 
Radio & Geoastronomy Division, 60 Garden St, Cambridge, MA 02138, USA
Telephone:  1 617-495-7194             FAX:  1 617-495-7345
Internet:  greenhill at cfa.harvard.edu   http://cfa-www.harvard.edu/~lincoln


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