NOAA-15, ALL, Heads Up on N15 Z_Wheel (Pitch), 21 June 2006 - Issued: 26 June 2006; 1645 UTC

Heads Up on N15 Z_Wheel (Pitch)

Date/Time(UTC) Message Issued:
26 June 2006, 1645 UTC

Satellite(s) Involved:

Instrument(s) Involved:

Product(s) Involved/Affected:

Date/Time(UTC) of Initial Implementation:
21 June 2006, Time TBC UTC

Details/Specifics of Change:
SOCC is reporting the following anomaly as a "heads up".
"EMOSS engineers have detected unusually large pitch errors on N15 in the past several days. These errors appear to be caused by the Z-reaction wheel (pitch) sticking as it crosses through 0 RPM from a negative to a positive speed (or vice versa) just like it occurs on N12 (see most recent Weekly Report). For a long time the N15 pitch wheel has operated at a negative speed. In early June it began to transition, much like N18 has done twice since launch, to the opposite speed (while pitch momentum does the opposite). As of 21 June, the speed began to cross through 0 RPM for the first time. As it crossed through 0, it typically sticks. The longer it sticks, the larger the pitch error. It is anticipated that N15 wheel speed will transition to the point where it does not cross over 0 anymore and thereby will not stick and perturb pitch. The transition will probably take several weeks. In the meantime, pitch perturbations are expected to continue. " See attached charts.

NOAA-15 2006A NOAA-15 2006B

NOAA-15 2006C NOAA-15 2006D

Contact Person(s) Name/Email/Phone Number for Questions: SOCC engineer ext. 117 with ops questions

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

* Emily D. Harrod
* Computer Operations Branch
* Pre-Product Processing Group
* E/SP11, Federal Building #4, room 0318
* 5200 Auth Road
* Suitland, Maryland 20746-4304
* voice 301-457-5247 ext 117
* fax 301-457-5199
* email