AAPP V4.2 Update Release, 13/02/2004
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Some passes of NOAA-16 give navigation errors of approximately 50km for AMSU. 
This can be seen, for example, when displaying AMSU-B channel 16 together with 
a coastline. The problem affects AMSU-A and AMSU-B, not HIRS. It affects 
locally processed HRPT data and EARS products, but not global NESDIS 1b data. 
It was first noticed in early January.

The cause has been traced to a slight variability in the synchronisation
of the AIP minor frames and TIP minor frames relative to each other and
to the HRPT frames. (AIP contains AMSU data; TIP contains HIRS and also
provides the timing reference for AMSU). This has been causing problems
in the AAPP decommutation stage: when the TIP timing reference arrives
late the AMSU data are tagged with a time that is 8 seconds in error.

A revised version of atovdc.F is attached which should cure the problem.
To install, copy it to directory
./AAPP/sources/decommutation/decommutation, then rebuild the
decommutation program (option 6 then sub-option 12 in INST_4).