During the last week, the observing schedule was interrupted due to a radiation monitor threshold violation. The loads were autonomously halted at 1:52am EDT on Jun 1 by the ACIS radiation monitor through execution of SCS 107 for SI safing. All spacecraft actions were nominal. A real-time procedure was executed on Jun 1 to disable SCS-29, which was enabled during the safing sequence. Loads for a replanned schedule were uplinked on Jun 2. Planned observations that were impacted by the interruption will be rescheduled.

Real-time procedures were executed on Jun 4 to perform a routine self-check of the Electrical Interface Assembly (EIA) Sequencer and to perform a diagnostic dump of the Control Processing Electronics (CPE).

A Chandra press release was issued on Jun 4 describing observations of two galaxy clusters that are making another pass at each other after colliding about a billion years ago. Known as PSZ2 G181 for short, this system has been studied in radio waves and reveals a pair of huge, parentheses-shaped structures outside the system. These structures are probably shock fronts — similar to those created by supersonic jets — likely caused by disruption of gas from the initial collision. Data from NASA’s Chandra and ESA’s XMM-Newton provide evidence that the two galaxy clusters are poised for another collision in the future. For details see: https://chandra.harvard.edu/photo/2025/g181/

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