Subject: Administrative: NOAA-18 change in attitude control mode This is a multi-part message in MIME format. --Boundary_(ID_Bzj4p2YQDfbcRawYTGwa0Q) Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 8BIT *Topic: * ** ****NOAA-18 change in attitude control mode from RGYRO (Reduced Gyro) estimate roll to GYE (Gyroless) estimate yaw, roll, and pitch in preparation of the second laser gyro reaching end of life any time in the next 5 months.The second laser gyro has reached its end of life design threshold that has margin before a hard failure.The first laser gyro failure lasted about 5 months from the design end of life threshold to a hard failure.Past performance would suggest leaving the attitude control mode as is for a longer period of time but past performance from a system risk point of view says that the second laser gyro could fail any time during this 5 month period or longer. Present attitude control mode is within spec of 0.2 degs per axis for attitude pointing.In GYE the attitude pointing will be in spec for roll and pitch and slightly out of spec for yaw (on average of 0.35 degs).This result was from our on-orbit testing of the enhanced RGYRO/GYROLESS software testing that was done in February of 2012.All products from NOAA-18 were acceptable to the users. * Date/Time Issued: *January 08, 2015 2340 UTC ** *Product(s) or Data Impacted: ***All data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV)* **Date/Time of Initial Impact: *January 13, 2015, Time 14:56 UTC *Date/Time of Expected End:***Within the next 5 months* Length of Outage:* **5 months or less* **Details/Specifics of Change:* On January 13, 2015 at 14:56 UTC (orbit 49726) the attitude mode on NOAA-18 will be changed from RGYRO (Reduced Gyro) estimate roll to GYE (Gyroless) estimate yaw, roll, and pitch in preparation of the second laser gyro reaching end of life any time in the next 5 months.The performance of NOAA-18 instrument L1b data in GYE is expected to be better than that of NOAA-15, which has been operating 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). NOAA-18 MIMU 1 Laser GYRO became operational on June 7, 2009 after MIMU 2 X Ring Laser Gyro (RLG) axis failed due to neon depletion. The MIMU1 Z axis gyro failed on 07 March 2014 (14/066) at 17:46:19 UTC. Use of the Z axis gyro was discontinued on 09 Oct 2013 (13/292), and ADACS was configured to operate in the RGYRO ESTIMATE ROLL mode on MIMU1 at that time. MIMU 1 Y axis Laser Intensity Monitor (LIM) values have been dropping steadily and that behavior is suspected to be an indication of the 'end of cathode life'.The MIMU 1 Y axis has reached a threshold where _further_ reduced gyro software is now necessary for stable Attitude control.NOAA-18 goes from 2 axes gyro control with the with the third axis now derived from the remaining two good gyro axes by flight software to gyroless control for period of 5 months or less where all axes control is derived by flight software using the ESA (earth sensor array) to 1 axis gyro control with the remaining 2 axes now derived from the remaining good gyro axis and the ESA (earth sensor array) by flight software. The final attitude control mode at the end of 5 months or sooner requires an additional flight software patch which is ready to be uploaded to the spacecraft.The spacecraft will be configured to Reduced Gyro (RGYRO) Mode Estimated Roll/Pitch (ESTY/Z) for the failed laser gyro y/z axes.Attitude errors for yaw, roll, and pitch are expected to be _again_ in spec (spec is 0.2 degrees per axis). *Contact Information*: ESPC Operations at ESPCOperations@noaa.gov and 301-817-3880 *Web Site(s) for applicable information:* See http://www.ssd.noaa.gov/PS/SATS/messages.html for this and other satellite related messages. See http://www.eumetsat.int/website/home/Satellites/CurrentSatellites/Metop/index.html for more information Metop satellites 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_Bzj4p2YQDfbcRawYTGwa0Q) Content-type: text/html; charset=ISO-8859-1 Content-transfer-encoding: 7BIT Topic:  

NOAA-18 change in attitude control mode from RGYRO (Reduced Gyro) estimate roll to GYE (Gyroless) estimate yaw, roll, and pitch in preparation of the second laser gyro reaching end of life any time in the next 5 months.  The second laser gyro has reached its end of life design threshold that has margin before a hard failure.  The first laser gyro failure lasted about 5 months from the design end of life threshold to a hard failure.  Past performance would suggest leaving the attitude control mode as is for a longer period of time but past performance from a system risk point of view says that the second laser gyro could fail any time during this 5 month period or longer.  

Present attitude control mode is within spec of 0.2 degs per axis for attitude pointing.  In GYE the attitude pointing will be in spec for roll and pitch and slightly out of spec for yaw (on average of 0.35 degs).  This result was from our on-orbit testing of the enhanced RGYRO/GYROLESS software testing that was done in February of 2012.  All products from NOAA-18 were acceptable to the users. 

Date/Time Issued: January 08, 2015  2340 UTC

Product(s) or Data Impacted:   All data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV)

 Date/Time of Initial Impact:  January 13, 2015, Time 14:56 UTC
 
 Date/Time of Expected End:  Within the next 5 months

Length of Outage:  5 months or less
 
Details/Specifics of Change:   On January 13, 2015 at 14:56 UTC (orbit 49726) the attitude mode on NOAA-18 will be changed from RGYRO (Reduced Gyro) estimate roll to GYE (Gyroless) estimate yaw, roll, and pitch in preparation of the second laser gyro reaching end of life any time in the next 5 months.  The performance of NOAA-18 instrument L1b data in GYE is expected to be better than that of NOAA-15, which has been operating 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).

NOAA-18 MIMU 1 Laser GYRO became operational on June 7, 2009 after MIMU 2 X Ring Laser Gyro (RLG) axis failed due to neon depletion.  The MIMU1 Z axis gyro failed on 07 March 2014 (14/066) at 17:46:19 UTC.  Use of the Z axis gyro was discontinued on 09 Oct 2013 (13/292), and ADACS was configured to operate in the RGYRO ESTIMATE ROLL mode on MIMU1 at that time.

MIMU 1 Y axis Laser Intensity Monitor (LIM) values have been dropping steadily and that behavior is suspected to be an indication of the ‘end of cathode life’.  The MIMU 1 Y axis has reached a threshold where further reduced gyro software is now necessary for stable Attitude control.  NOAA-18 goes from 2 axes gyro control with the with the third axis now derived from the remaining two good gyro axes by flight software to gyroless control for period of 5 months or less where all axes control is derived by flight software using the ESA (earth sensor array) to 1 axis gyro control with the remaining 2 axes now derived from the remaining good gyro axis and the ESA (earth sensor array) by flight software.  

The final attitude control mode at the end of 5 months or sooner requires an additional flight software patch which is ready to be uploaded to the spacecraft.  The spacecraft will be configured to Reduced Gyro (RGYRO) Mode Estimated Roll/Pitch (ESTY/Z) for the failed laser gyro y/z axes.  Attitude errors for yaw, roll, and pitch are expected to be again in spec (spec is 0.2 degrees per axis). 

Contact Information:  ESPC Operations at ESPCOperations@noaa.gov and 301-817-3880

Web Site(s) for applicable information:  See http://www.ssd.noaa.gov/PS/SATS/messages.html for this and other satellite related messages.

See http://www.eumetsat.int/website/home/Satellites/CurrentSatellites/Metop/index.html for more information Metop satellites


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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