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NOUS41 KWBC 141535
PNSNMC
NATIONAL TECHNICAL INFORMATION MESSAGE /NTEM/ 97-5
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
1030 AM EST TUE JAN 14 1997
TO: FAMILY OF SERVICES /FOS/ SUBSCRIBERS...NOAA WEATHER
WIRE SERVICE /NWWS/ SUBSCRIBERS...OTHER NATIONAL
WEATHER SERVICE /NWS/ CUSTOMERS...NWS EMPLOYEES
FROM: ROBERT S. WINOKUR
ASSISTANT ADMINISTRATOR FOR NATIONAL ENVIRONMENTAL
SATELLITE...DATA...AND INFORMATION SERVICES /NESDIS/
RON S. GIRD
NWS OFFICE OF METEOROLOGY SATELLITE PROGRAM MANAGER
SUBJECT: LATEST UPDATE GOES-8 SATELLITE STATUS /AS OF JAN 14/
AT 8:45 P.M. EST ON JANUARY 10 THE GOES-8 SATELLITE WAS
RETURNED TO SERVICE. THE SATELLITE IS NOW OPERATING IN WHAT WE
CALL THE "L" MODE WITH THE BACKUP /SMALLER REACTION WHEEL/
REPLACING THE SECOND LARGER MOMENTUM WHEEL FOR SPACECRAFT
STABILIZATION. THE SPACECRAFT STOPPED PROVIDING IMAGES AT 8:30
A.M. JANUARY 9. DURING THE OUTAGE 182 IMAGES AND 73 SOUNDINGS
WERE MISSED.
WE COMPLETED A RECOVERY SCHEDULE /ABBREVIATED FULL
DISKS...EXTENDED STAR WINDOWS/ THAT EXTENDED FOR 36 HOURS TO
ALLOW THE IMAGE NAVIGATION AND REGISTRATION /INR/ SYSTEM TO
SETTLE BACK INTO ACCEPTABLE PERFORMANCE. USERS DID EXPERIENCE
LARGER THAN NORMAL INR ERRORS DURING THAT TIME.
THE "L" MODE HAS NEVER BEEN USED OPERATIONALLY ON GOES AND
DOES REQUIRE THE WHEELS TO RUN AT A FASTER SPEED THAN NORMAL BUT
STILL WITHIN SPECIFICATION. WHILE GOES-8 HAS BEEN TESTED USING
THE REACTION WHEEL SYSTEM...WE HAVE NOT PREVIOUSLY PERFORMED
IMAGING AND SOUNDING OPERATIONS IN THIS MODE. INR PERFORMANCE...
WHILE ACCEPTABLE...IS NOT FULLY CHARACTERIZED. IT IS LIKELY THAT
THE CORRECTIONS THAT WE ROUTINELY MAKE FOR THE "BATWING"
ANOMALY...THE MAGNETOMETER "BOOM SNAP," AND EARTH SENSOR SINGLE
CHORD OPERATION WILL REQUIRE RECALIBRATION. USERS...THEREFORE
...SHOULD EXPECT LARGER THAN NORMAL ERRORS AT MIDNIGHT AND FROM
1830Z TO 1900Z UNTIL THESE SYSTEMS ARE CORRECTED. WITH 3 DAYS OF
DATA THE PERFORMANCE OF THE CONTROL SYSTEM APPEARS NOMINAL...
ALTHOUGH THERE HAVE BEEN SOME MECHANICAL INTERACTIONS BETWEEN THE
MOMENTUM WHEEL AND THE EARTH SENSOR WHICH WILL REQUIRE FURTHER
INVESTIGATION. THESE INTERACTIONS...WHICH WERE CHARACTERIZED
DURING THE GOES-8 POST LAUNCH TESTING...DO NOT APPEAR TO IMPACT
IMAGING BUT MAY REQUIRE SOME WHEEL SPEED ADJUSTMENTS.
THE ANOMALY APPEARS TO HAVE BEEN CAUSED BY A FAILURE WITHIN
THE WHEEL DRIVE ELECTRONICS FOR MOMENTUM WHEEL 1. THIS CAUSED
THE LOSS OF MOMENTUM WHEEL SPEED DATA TO THE ATTITUDE AND ORBIT
CONTROL ELECTRONICS /AOCE/ COMPUTER. THE LOSS LEAVES GOES-8 WITH
NO MOMENTUM WHEEL REDUNDANCY. THE AOCE AND THE REST OF THE
SPACECRAFT REMAIN NOMINAL. NOAA...NASA AND SPACE
SYSTEMS/LORAL ENGINEERS ARE LOOKING AT A POSSIBLE ALTERNATIVE
MODES OF OPERATION TO REGAIN SOME LEVEL OF REDUNDANCY.
NESDIS
P.S. THERE WILL BE IMPACTS TO THE GOES PRODUCTS ESPECIALLY
GOES-8 PRECIPITATION ESTIMATES...GOES/ASOS CLOUD PRODUCTS...AND
THE FOG PRODUCT. WE ARE TRYINGTO QUANTIFY THE
NAVIGATION/GRIDDING IMPACT TO THESE PRODUCTS. WE WILL KEEP
POSTED..... RON GIRD OM22.
END
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