Subject: Administrative: NOAA-18 Attitude Control Mode Change for --001a113c35243ee58a05556238a6 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable *Topic:* NOAA-18 Attitude Control Mode Change for Yaw, Roll, and Pitch *Date/Time Issued:* July 28, 2017 15:20 UTC *Product(s) or Data Impacted:* All data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV) might be impacted *Date/Time of Initial Impact:* August 9, 2017 15:07:50 UTC *Date/Time of Expected End: * Permanent *Length of Outage: * Permanent *Details/Specifics of Change:* The last laser gyro on NOAA-18 in MIMU 1 (Miniature Inertial Measure Unit #1) for Yaw is expected to reach critical LIM (Laser Intensity Measure) threshold August 12-15, 2017. Engineering has chosen to be proactive and change the attitude control mode to GYE (Gyroless) before this date on Wednesday morning August 09, 2017 (jday 221) at 15:07:50 UTC Rev 62980. This action will avoid risk of autonomous spacecraft intervention. Engineering expects attitude pointing for roll and pitch will remain in spec with nominal Yaw errors better than =C2=B10.5 degrees (about 7.5 km) o= ver 95% of the orbit. AVHRR imagery at scan edges will show geolocation errors but should be usable for fire and snow/ice products and users. Other instruments have a larger FOV (Field of View) and hence this increase in Yaw pointing error above spec of 0.2 degrees is nullified. 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 estimated Yaw, and equivalent to the operation of NOAA-18 in GYE from Jan 13, 2015 until Dec 15, 2015 when the s/c was in an attitude control mode transition. 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. The MIMU 1 Z and Y axes reached their critical threshold where reduced gyro software was necessary for stable Attitude Control on October 9, 2013 and January 06, 2015 respectively. The MIMU 1 Z and Y axes failed on March 7, 2014 and July 5, 2015, five to six months after reaching their respective critical thresholds. Final failure of the X axis is expected to occur much sooner than five months after reaching critical threshold. The design lifetime of these MIMU units was 4 years with the laser ring gyros (LRG) being the limiting component. NOAA-18 went from 3 to 2 to 1 to 0 axes gyro control with the missing axes now being derived from the remaining good gyro axes and the ESA (Earth Sensor Array) by flight software. The enhanced ACS (Attitude Control System) flight software developed by the POES Team extended the life of NOAA-18 by about 4 years meeting attitude error spec of 0.2 degrees per axis. The GYE attitude control mode will now allow for several more years of operation of NOAA-18 with good attitude pointing errors for Yaw, Roll, and Pitch. An ESPC reminder notice will also be sent out shortly before this attitude control mode change to GYE on NOAA-18. *Web Site(s) for applicable information:* N/A *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 This message was sent from 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. --001a113c35243ee58a05556238a6 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
= Topic: NOAA-18 Attitude Control Mode Change for Yaw, Roll, and Pitch=

Date/Time Issued: =C2=A0July 28, 2017 15:2= 0 UTC

Product(s) or Data Impacted: =C2=A0Al= l data and products from NOAA-18 (AVHRR, AMSU-A, HIRS, MHS, & SBUV) mig= ht be impacted =C2=A0

Date/Time of Initial Impa= ct: =C2=A0August 9, 2017 =C2=A015:07:50 UTC

Date/Time of Expected End: =C2=A0Permanent=C2=A0

<= div>Length of Outage: =C2=A0Permanent=C2=A0

Details/Specifics of Change: =C2=A0The last laser gyro on NOAA-18 i= n MIMU 1 (Miniature Inertial Measure Unit #1) for Yaw is expected to reach = critical LIM (Laser Intensity Measure) threshold August 12-15, 2017.=C2=A0 = Engineering has chosen to be proactive and change the attitude control mode= to GYE (Gyroless) before this date on Wednesday morning August 09, 2017 (j= day 221) at 15:07:50 UTC Rev 62980. This action will avoid risk of autonomo= us spacecraft intervention.

Engineering expects at= titude pointing for roll and pitch will remain in spec with nominal Yaw err= ors better than =C2=B10.5 degrees (about 7.5 km) over 95% of the orbit.=C2= =A0 AVHRR imagery at scan edges will show geolocation errors but should be = usable for fire and snow/ice products and users.=C2=A0 Other instruments ha= ve a larger FOV (Field of View) and hence this increase in Yaw pointing err= or above spec of 0.2 degrees is nullified. =C2=A0

= The performance of NOAA-18 instrument L1b data in GYE is expected to be bet= ter than that of NOAA-15, which has been operated in the enhanced Reduced G= yro Mode since March 17, 2010 in estimated Yaw, and equivalent to the opera= tion of NOAA-18 in GYE from Jan 13, 2015 until Dec 15, 2015 when the s/c wa= s in an attitude control mode transition. =C2=A0

N= OAA-18 MIMU 1 GYRO became operational on June 7, 2009 after MIMU 2 X Ring L= aser Gyro (RLG) axis failed due to neon depletion.=C2=A0 The MIMU 1 Z and Y= axes reached their critical threshold where reduced gyro software was nece= ssary for stable Attitude Control on October 9, 2013 and January 06, 2015 r= espectively.=C2=A0 The MIMU 1 Z and Y axes failed on March 7, 2014 and July= 5, 2015, five to six months after reaching their respective critical thres= holds.=C2=A0 Final failure of the X axis is expected to occur much sooner t= han five months after reaching critical threshold.=C2=A0 The design lifetim= e of these MIMU units was 4 years with the laser ring gyros (LRG) being the= limiting component.=C2=A0 NOAA-18 went from 3 to 2 to 1 to 0 axes gyro con= trol with the missing axes now being derived from the remaining good gyro a= xes and the ESA (Earth Sensor Array) by flight software.=C2=A0 The enhanced= ACS (Attitude Control System) flight software developed by the POES Team e= xtended the life of NOAA-18 by about 4 years meeting attitude error spec of= 0.2 degrees per axis.

The GYE attitude control mo= de will now allow for several more years of operation of NOAA-18 with good = attitude pointing errors for Yaw, Roll, and Pitch. =C2=A0

An ESPC reminder notice will also be sent out shortly before this a= ttitude control mode change to GYE on NOAA-18.

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

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

This message was sent from 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 a= t ESPCOperations@noaa.gov or= (301) 817-3880. Please note: it may take up to two business days to proces= s your unsubscribe request.
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