Ed S#DSCOVR in safe mode at L1, a million miles away... a #spacecraft with a long history. Thanks Al Gore!
"DSCOVR has been designed for a Gyro-Less Safe Mode Attitude Control – relying only on sun sensor readings and information from the reaction wheels. The safehold system uses wheel tachometers to estimate spacecraft body rates about the sun vector in order to achieve a sufficient accuracy in sun-pointing during safe mode periods."
Lots of info:
http://spaceflight101.com/dscovr
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