During the last week the Chandra observing schedule was interrupted at 2:36pm EDT on Aug 19 by what was likely a single event upset (SEU) in the telemetry processor of the Command and Telemetry Unit, causing a reset of its timing signals and resets of several spacecraft components. An elevated temperature of the aspect camera CCD due to the resets led to its losing track of stars resulting in the spacecraft entering normal-sun mode. All safing actions were nominal.

Recovery activities were successfully executed Aug 19-20 following standard operating procedures for recovering from a CTU reset and recovering from Normal Sun Mode. The OBC-A and -B memory were dumped as a follow-up to the flight software patch. The dumps will be used to update the baseline memory images maintained on the ground.

In addition to the real-time procedures associated with the CTU reset recovery, real-time procedures were executed on Aug 19 and Aug 22 to initiate long ACIS CTI data collection while waiting to return to observing science.

A new mission schedule was uplinked on Aug 22, which resumed science observations at 10:32am EDT on Aug 23. There were 257.0 ks of science loss due to the anomaly. Planned observations were impacted by the interruption and will be rescheduled.

Another real-time procedure was executed on Aug 25 to check out HRC-I operation on the A-side electronics. As part of the continued evaluation of the HRC, the HRC 15V power supply was successfully powered on for approximately 10 ks and an HRC-I science observation of TYC 6991-475-1 was completed.

The schedule of targets for the next week is shown below.