Pre-Product Processing staff and users have detected several inconsistencies
in the parallel test data for the NOAA-16 HIRS, AMSU-B, and HRPT data.
Those problems have been identified and corrected where needed. The
parallel test data is now the same as the operational data except for the
changes that we noted in our initial change notice. Because these problems
have made it difficult for you to verify that the test data meets your
needs, we are changing the scheduled implementation date to December 14
rather than December 12. We are making every effort to implement the
changes before our mandatory freeze period is reached (from December 15
through January 6, no changes are allowed to operational software or
We apologize for any problems that this is creating for you. We appreciate
your continued cooperation and support. Below is an explanation of the
corrections that had to be made to the parallel tests and information on why
you see some differences or errors not seen in the NOAA-15 data.
In the parallel test, the NOAA-15 HIRS calibration was different from the
ops because the 24-hour file was not updated for the data provided before
day 341. That has been corrected now and updated data will be place on the
ftp sites this morning (It has already been placed on the psbsgi1 site).
Please accept my apologies for not having all of this in place from the
The HIRS 1B for NOAA-16 is reflecting calibration problems that will be
corrected as soon as we change the algorithm that updates our 24-hour file.
Since NOAA-16 is not operational this can be done over the freeze period
without impacting other satellites. The permanent fix will be implemented
as soon as possible after the freeze is lifted.
Clock corrections for NOAA-16 are turned on in the test data, but we are
seeing adjustments of +/-500 ms in the clock error that last for several
days. We are adjusting for the change once it is detected. Depending on
which set of data you examine you will see descending passes with a very
small along track error or an error of about 500 ms. Both of these errors
are significantly smaller than the error without clock corrections turned on
as seen in the ops data.
We believe that the small differences you see in the NOAA-16 AMSU-B are due
to a change to correct for moon glint. The instrument scientist felt that
the correction should be incorporated in with other similar anomalous
corrections and should be flagged under the existing indicators as shown
below. The quality of the data will determine if differences other than
moon glint will show up (this will effect calibration).
Existing Level 1B indicators:
Calibration Quality Flags (all bits off implies a good calibration)
Bits set per channel
bit 4: All bad space view counts for scan line
bit 1: Marginal space view counts for this line
Existing level 1B* indicators:
array item 2: no good space view counts for scan line
array item 5: Some bad space view counts for scan line
Please contact us if you have questions or problems.
Emily D. Harrod
E/SP13 Room 0308 FB#4
5200 Auth Road
Suitland, Md. 20746-4304