EOP Update

We recommend that all VLBA users update the predicted or first-look Earth Orientation Parameters used by the VLBA correlator to the final values available from USNO. This is done in AIPS with the task CLCOR, _or_ with the procedure VLBAEOPS, which invokes CLCOR.

For details, see: http://www.vlba.nrao.edu/astro/messages/eop/eop05Oct06.

The recent leap second unearthed a bug in CLCOR, now fixed. Users should update their installation of AIPS with the midnight job. Help is available at: http://www.aoc.nrao.edu/aips/#MNJ or by email to daip@nrao.edu.

The bug was that CLCOR, run on data observed after 1 Jan2006, effectively used the wrong value for the leap second. The symptom is that the "USNO" and "Used by Correlator" values, as reported by CLCOR at execution, differed by 1 second. They should differ by a few milliseconds at most. CLCOR run on data prior to 01 Jan2006 works correctly when TAI-UTC is 32 seconds; it is now 33.

Copyright © 2009 Associated Universities, Inc.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.