Operational Restrictions Due to Single-Gyro Mode

Francis Vandenbussche explained the operational restrictions resulting from the loss of gyros A and C (annex 5), and polled the PIs about the effect that abandoning the roll steering law could have in the operations and science coming from their instruments. This would imply no North/South spacecraft orientation during several weeks per year in order to always keep a bright start in the SSUs. The result of the poll was:

• VIRGO/LOI needs the North/South alignment in order to work, so the correct roll attitude is a requirement.
• MDI would need a more complex calibration. Also, each different spacecraft roll attitude would require a different calibration, so abandoning the roll steering law will make life much more difficult.
• GOLF is insensitive
• SUMER to be studied.
• CDS no problem.
• EIT would be able to live without the roll steering law, but the maximum resolution on synoptic charts would be degraded.
• LASCO: complicates the calibration mainly for C3. Same situation as MDI.
• SWAN no effect.
• CELIAS no effect.
• COSTEP no effect.
• ERNE no effect.