NOAA-17 Level 1Bs Operational and Clock Corrections, 24 August 2002 - Issued: 23 August 2036; 2000 UTC

Operational Status of NOAA-17 Level 1B Data and Clock Corrections

Date/Time(UTC) Message Issued:
23 August 2002 2036 UTC

Satellite(s) Involved:

Instrument(s) Involved:

Product(s) Involved/Affected:
Level 1B files and Clock Drift File

Date/Time(UTC) of Initial Implementation:
24 August 2002

Details/Specifics of Change:

MEMORANDUM FOR: All NOAA-17 Level 1B Data Users

FROM: Barbara A. Banks
Chief, Information Processing Division

SUBJECT: Operational Status of NOAA-17 Level 1B Data

On August 24, the Information Processing Division (IPD) will declare all the
National Oceanic and Atmospheric Administration (NOAA)-17 level 1B data
operational. These data are available to the user community:

AVHRR Advanced Very High Resolution Radiometer
HRPT - High Resolution Picture Transmission
LAC - Local Area Coverage
GAC - Global Area Coverage
AMSU-A Advanced Microwave Sounding Unit-A
AMSU-B Advanced Microwave Sounding Unit-B
HIRS High Resolution Infrared Radiometer
SEM Space Environment Monitor
DCS Data Collection System
SAR Search and Rescue
SBUV Solar Backscatter Ultraviolet Spectrometer

The following anomalies in NOAA-17 data have been identified and corrected
or will be corrected in an operational mode.

HIRS - On July 11, as of orbit B0023637, the scan mirror temperature sensor
failed completely. Prior to this, it was intermittent. This should have no
impact on level 1B and product processing. Michael Chalfant, Office of
Research and Applications (ORA), examined imagery produced from NOAA-17 HIRS
data and made recommendations for updates to the level 1B processing.

On the afternoon of July 11, the following changes were introduced into
1. Due to possible contamination in the space view samples, the number of
space view samples used in processing has been reduced from 45 to 40 making
it compatible with NOAA-16.
2. A constant roll type attitude correction of 1.8 degrees was introduced
to correct an apparent across track error that appears to be the same as in

AMSU-A - Channel 3 is demonstrating intermittent 30 count drops in the space
and warm target values during the descending portion of some orbits.
Internal data users indicate that this does not create a problem for their
product processing. The National Environmental Satellite, Data, and
Information Service (Satellite Operations Control Center - SOCC, ORA, and
IPD), and the National Aeronautics and Space Administration are working
together to determine the source of this anomaly. Dr. Tsan Mo, ORA
instrument scientist, has recommended a software fix for the level 1B
processor calibration coefficient computation. IPD will integrate, test,
and implement this change as a normal operational update. Users will be
notified when test data is available.

One final item of note for the level 1B and direct readout data users.
Clock error adjustments for NOAA-17 are being handled in a different manner
than for the other NOAA polar satellites. On July 30, SOCC began making
daily updates to the spacecraft clock to account for the drift error (daily
corrections of 0.6 msec). The current drift rate is about -0.7 msec/day.
SOCC will continue to monitor the clock error closely. Users will be
notified of any changes.

Contact Person(s) Name/Email/Phone Number for Questions:
Emily D. Harrod/ ext 117

Web site(s) that contain other relevant information (where applicable): - SOCC morning reports - History of level 1B