Chandra entered Normal Sun Mode (NSM) at 12:51pm EDT on Sep 5 as the result of a recurrence of the transient ACA high-background anomaly which caused loss of guide stars. In this situation the ACA CCD background level increases rapidly and unexpectedly to the point where the guide star flux is overwhelmed by the background. This has occurred many times during the mission and has previously been benign because the duration was short enough to avoid a safing action. On Sep 5, however, the event lasted long enough to cause the transition to NSM. The root cause of the background increase has not been established but is believed to stem from scattered light that directly illuminates the ACA CCD. The NSM recovery operations took place on Sep 5 and observations are planned to resume on Sep 6 at 7:30pm EDT with 93.0ks of science loss. Scheduled observations that were impacted by the anomaly will be rescheduled in future weeks.

In addition to the real-time procedures associated with the NSM recovery, a real-time procedure was executed on Sep 5 to initiate a long ACIS CTI data collection while waiting to return to observing science.

Additional real-time procedures were executed on Aug 30 and Sep 2 to perform full-frame dark current readouts of the Aspect Camera Assembly CCD and on Sep 4 to perform a routine self-check of the Electrical Interface Assembly (EIA) Sequencer.