NOAA-16,All Instruments, Dwell Test Gyro -1 Anomaly investigation, 27 October 2005- Issued: 27 October 2005; time issued 2000 UTC

Dwell test to investigate gyro-1 anomaly

*Date/Time(UTC) Message Issued:*
27 October 2005/2000 UTC

*Satellite(s) Involved:*

*Instrument(s) Involved:*
All Instruments

*Product(s) Involved/Affected:*
All products

*Date/Time(UTC) of Initial Implementation:*
27 October 2005, 2021 UTC

*Details/Specifics of Change:*
On 24 Oct at 18:00z, the SOCC detected a gyro anomaly on NOAA-16.
Engineers determined that the IMU Logic board switched sides due to a
sharp increase in the spin motor current on gyro#1. There was a similar
increase in gyro#2 motor current as a result of the logic board switch.
The motor current subsequently decreased significantly on both gyros -
decreasing by 15-20 mamps and remaining steady at the new level. Back
orbit data showed that the anomaly began at 14:59:07z. Initial
investigations indicate that a slipped pole in gyro#1 motor which could
stall the motor leading to serious damage to the IMU and loss of
attitude control may be the cause. On rev 26538, 22:45z SOCC commanded
gyro #1 off and placed the spacecraft in reduced gyro mode - estimate
roll. The spacecraft is operating nominally in this mode.

SOCC engineers are continuing their investigation into the anomaly and
plan to do the following beginning around 2021z on October 27 (rev 26279).

- Set spacecraft telemetry for 1 second attitude rates and raw IMU data.
- Implement 2 dwells; one high speed swell for about 1 minute (60
seconds); the other analog 1 second dwell on roll reaction wheel motor

Most other data will be lost during the high speed dwell (60 seconds of

*Contact Person(s) Name/Email/Phone Number for Questions:* 301-817-4117 - SOCC operations 301-457-5247 ext. 117 - IPD operations

*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
* Product Systems Branch
* Pre-Product Processing Group
* E/SP13, Federal Building #4, room 0318
* 5200 Auth Road
* Suitland, Maryland 20746-4304
* voice 301-457-5247 ext 117
* fax 301-457-5199
* email