SOHO spacecraft is in Emergency Sun Reacquisition (ESR) mode

By Keith Cowing
November 29, 1999
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According to a NASA status report: “On Sunday, 1999 November 28, while in normal mode collecting routine science data, the computer for the SOHO’s Attitude Control Unit A (ACU) reset for an undetermined reason. This automatically triggered a switch to the Emergency Sun Reacquisition (ESR) mode. ESR is an automatic reconfiguration of the Attitude and Orbit Control Subsystem (AOCS). If a transition from ESR to Coarse Roll Pointing (CRP) occurs on schedule, a spacecraft momentum management will be performed on Tuesday, 1999 November 30, and the instruments returned to normal scientific operations shortly thereafter. We expect a complete recovery well before the 4th anniversary of SOHO’s launch on December 2.”

° SOHO website

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