Subject: Administrative: NOAA-18 MIMU 1 RGYRO axis failure This is a multi-part message in MIME format. --Boundary_(ID_CPbwe9/3IUBMdkljINe8og) Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 8BIT *Topic: *NOAA-18 Upload of Alignment matrix for the Failing Gyro axis and MIMU1OPS FSW patch for Attitude Control Mode. *Date/Time Issued:* September 27, 2013, 2010 UTC *Product(s) Involved/Affected:* All data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV) *Date/Time of Initial Implementation:*October 9, 2013, Time 12:49 UTC *Date/Time of Expected End: *October 9, 2013, Time 16:11 UTC *Length of Outage: *3.5 hours *Details/Specifics of Change:*From 9 October 2013 at 12:49 UTC (orbit 43219) to 9 October 2013 at 16:11 UTC (orbit 43221), NOAA-18 will be placed into Gyroless (GYE) Mode when uploading the alignment matrix for the failed gyro axis and the MIMU1OPS Flight Software patch which might require up to 2 passes to complete its upload. Products may be impacted by larger than normal yaw attitude disturbances. The performance of NOAA-18 instrument L1b data in GYE is expected to be better than that of NOAA-15, which has been operated in the enhanced Reduced Gyro Mode since March 17, 2010 in estimate yaw. Based on our 24 hour on-orbit GYE testing done on NOAA-18 and the extended 9 day on-orbit GYE testing done on NOAA-17, we expect roll and pitch errors will remain in spec with nominal yaw errors of about ±0.5 degrees (about 7.5 km). Upon completing the MIMU1OPS patch upload, the spacecraft will be configured to Reduced Gyro (RGYRO) Mode Estimated Roll (ESTY) for the failing laser gyro z axis. Attitude errors for yaw, roll, and pitch are expected to be in spec (spec is 0.2 degrees per axis). The performance of NOAA-18 instrument L1B is expected to be similar to that of NOAA-16 which has been operated in RGYO estimate roll since October of 2005. NOAA-18 MIMU 1 GYRO became operational on June 7, 2009 after MIMU 2 X Ring Laser Gyro (RLG) axis failed due to neon depletion. MIMU 1 Y and Z axes Laser Intensity Monitor (LIM) values have been dropping steady and that behavior is suspected to be an indication of the 'end of cathode life'. The MIMU 1 Z axis has reached a threshold where reduced gyro software is now necessary for stable Attitude control. NOAA-18 goes from 3 axes gyro control to 2 axes gyro control with the third axis now derived from the remaining two good gyro axes by flight software. *Products that use NOAA-18 that will be affected:* All data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV) might be affected. *Contact Information for Further Information:* ESPC Operations at ESPCOperations@noaa.gov at 301-817-3880 Carl Gliniak at carl.gliniak@noaa.gov at 301-817-4207 Dejiang Han at dejiang.han@noaa.gov at 301-817-4119 * Web Site(s) for applicable information:*N/A This message was sent by ESPC.Notification@noaa.gov. You have been sent this and other notifications because you have opted in to receive it. If for any reason, you wish to unsubscribe, please contact ESPC Help Desk at ESPCOperations@noaa.gov or (301) 817-3880. Please note: it may take up to two business days to process your unsubscribe request. --Boundary_(ID_CPbwe9/3IUBMdkljINe8og) Content-type: text/html; charset=ISO-8859-1 Content-transfer-encoding: 7BIT

Topic: NOAA-18 Upload of Alignment matrix for the Failing Gyro axis and MIMU1OPS FSW patch for Attitude Control Mode. 

Date/Time Issued:  September 27, 2013, 2010 UTC

Product(s) Involved/Affected:  All data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV)

Date/Time of Initial Implementation: October 9, 2013, Time 12:49 UTC

Date/Time of Expected End: October 9, 2013, Time 16:11 UTC

Length of Outage: 3.5 hours

Details/Specifics of Change: From 9 October 2013 at 12:49 UTC (orbit 43219) to 9 October 2013 at 16:11 UTC (orbit 43221), NOAA-18 will be placed into Gyroless (GYE) Mode when uploading the alignment matrix for the failed gyro axis and the MIMU1OPS Flight Software patch which might require up to 2 passes to complete its upload. Products may be impacted by larger than normal yaw attitude disturbances.  The performance of NOAA-18 instrument L1b data in GYE is expected to be better than that of NOAA-15, which has been operated in the enhanced Reduced Gyro Mode since March 17, 2010 in estimate yaw.  Based on our 24 hour on-orbit GYE testing done on NOAA-18 and the extended 9 day on-orbit GYE testing done on NOAA-17, we expect roll and pitch errors will remain in spec with nominal yaw errors of about ±0.5 degrees (about 7.5 km).

Upon completing the MIMU1OPS patch upload, the spacecraft will be configured to Reduced Gyro (RGYRO) Mode Estimated Roll (ESTY) for the failing laser gyro z axis.  Attitude errors for yaw, roll, and pitch are expected to be in spec (spec is 0.2 degrees per axis).  The performance of NOAA-18 instrument L1B is expected to be similar to that of NOAA-16 which has been operated in RGYO estimate roll since October of 2005. 

NOAA-18 MIMU 1 GYRO became operational on June 7, 2009 after MIMU 2 X Ring Laser Gyro (RLG) axis failed due to neon depletion. MIMU 1 Y and Z axes Laser Intensity Monitor (LIM) values have been dropping steady and that behavior is suspected to be an indication of the ‘end of cathode life’.  The MIMU 1 Z axis has reached a threshold where reduced gyro software is now necessary for stable Attitude control.  NOAA-18 goes from 3 axes gyro control to 2 axes gyro control with the third axis now derived from the remaining two good gyro axes by flight software. 

Products that use NOAA-18 that will be affected:
All data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV) might be affected. 

Contact Information for Further Information:
ESPC Operations at ESPCOperations@noaa.gov at 301-817-3880
Carl Gliniak at carl.gliniak@noaa.gov at 301-817-4207
Dejiang Han at dejiang.han@noaa.gov at 301-817-4119


Web Site(s) for applicable information: N/A

This message was sent by ESPC.Notification@noaa.gov. You have been sent this and other notifications because you have opted in to receive it. If for any reason, you wish to unsubscribe, please contact ESPC Help Desk at ESPCOperations@noaa.gov or (301) 817-3880. Please note: it may take up to two business days to process your unsubscribe request.

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