NOAA-16, AVHRR, Scan Motor Current Anomaly TCE Correction, 23 September 2003 - Issued: 22 September 2003; 2240 UTC

Mon 6:45 PM
Subject: NOAA-16, AVHRR, Scan Motor Current Anomaly TCE Correction, 23 September 2003 - Issued: 22 September 2003; 2240 UTC

Scan Motor Current and Synch Delta Anomaly - TCE Turnoff

Date/Time(UTC) Message Issued:
22 September 2003, 2240 UTC

Satellite(s) Involved:

Instrument(s) Involved:
All (since all data is synch to the AVHRR)

Product(s) Involved/Affected:
All products/increased instrument temperature

Date/Time(UTC) of Initial Implementation:
23 September 2003, Time 1356 UTC

Details/Specifics of Change:
On September 23 (day 266) on orbit 15478 around 1356 UTC, the Satellite
Operations Control Center (SOCC) will "turn off the TCE24 (AVHRR
Heater/Louver). This will be done in an attempt to heat up the AVHRR and
decrease the viscosity of the scan motor lubricant. The current thought is
that the lubricant has become too cold and thick reducing lubrication and
that heating up this lubrication will have the reverse effect. This was
shown to have worked on NOAA-12 10 years ago." SOCC will continue to
enable rephasing about twice a day or as needed. However, plans are to
automate rephasing once per day during the blind orbit (around 0430 UTC)
beginning on September 26. Users will be notified of any changes.

This procedure will be done in an effort to correct the AVHRR sync problems
observed over the past few days as reported in the initial message on
September 18. - "At approximately 07:00Z on 17 Sept, the N16 AVHRR scan
motor current and its synch delta word began to act erratically running up
as high as 287 mAmps (vs nominal 230). ...." In an attempt to maintain
data quality rephasing was disabled (starting on or about noon local on
September 18) and SOCC controllers began enabling rephasing once per shift
(on the first available contact per shift that time permits). "Operational
impacts are: 1) each time rephasing occurs there will be a drop in TIP
frames (1 or 2 frames) and 2) the pointing of the AVHRR may not be as
accurate in between times to rephase. Rephase will only occur if needed
during the time it is enabled as mentioned above."

Contact Person(s) Name/Email/Phone Number for Questions: ext. 117 ext. 129

Web site(s) that contain other relevant information (where applicable): - History of level 1B
notices - All user notices - SOCC polar satellites status - SOCC morning reports