Inappropriate EOP on the VLBA Correlator

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VLBA TEST MEMO 69

Inappropriate EOP on the VLBA Correlator

R. C. Walker, V. Dhawan, W. Brisken, J. Benson, L. Kogan, & J. Romney
National Radio Astronomy Observatory
Socorro, NM

October 6, 2005

Abstract:

A bug has been found in the job generator for the VLBA correlator that caused it to use predicted rather than measured Earth Orientation Parameters (EOP) between May 2003 and August 2005. The errors introduced often are sufficiently large to adversely affect phase referencing observations and other observations that rely on an accurate correlator model. The nature of the problem and its impact are discussed in this memo. Correcting data is straightforward using the new EOPS option in the AIPS task CLCOR. Users just wishing to make corrections without worrying about the gory details can consult Section 2, or simply follow the CLCOR help file. It has become apparent while dealing with this problem that even occasional projects from outside the time period of the bug have been correlated with poor EOP. Usually this is because their job scripts were prepared too close to the observe date. So any user depending on an accurate correlator model may wish to check their EOP.


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Craig Walker 2005-10-06

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