During the last week Chandra's observing schedule was interrupted by a spacecraft Safe Mode event that occurred at 12:32pm EDT on Oct 21. This was during the Normal Sun Mode (NSM) recovery procedure, which was being run to recover from the IU-A reset event on Oct 20. The Safe Mode transition was nominal. The cause of the trip was an unanticipated software condition which occurred when transitioning from NSM mode to Normal Maneuver Mode (NMM). In response to a previous Safe Mode in 2020, the momentum monitor sample interval in NMM had been was increased from 49 to 64 samples. The samples in Normal Sun Mode remained at 49. This mismatch allowed stale data into the calculation upon the transition from NSM to NMM. No hardware issues have been identified as contributing to the Safe Mode entry and the team has implemented procedural changes to prevent a recurrence.

Real-time procedures were executed over Oct 21-23 to recover from Safe Mode to OBC-A control in Normal Sun Mode and then recover to Normal Point Mode. As part of the Normal Sun Mode recovery, a maneuver to a cooling attitude was performed to prevent excessive spacecraft heating at the Normal-Sun attitude.

Additional real-time procedures were executed on Oct 23 to dump OBC-A and -B memory as a follow-up to the recovery actions. The dumps will be used to update the baseline memory images maintained on the ground.

In order to perform spacecraft cooling and control eclipse entry and exit of the 10th and 11th eclipses of the season on Oct 24 and Oct 27, a set of maneuver-only (non-science) loads were uplinked to the spacecraft during the 8 pm EDT contact on Oct 23. Chandra passed through these eclipses with nominal power and thermal performance.

A new mission schedule and loads were approved and began operating at 10:21am EDT on Oct 27. This anomaly resulted in 398 ks of science loss. Scheduled observations that were impacted by the Safe Mode will be rescheduled.

The schedule of targets for the next week is shown below and includes an observation of AT2022tsd, which is a follow-up to a Target of Opportunity which was accepted on Oct 7 and is coordinated with NuStar.