ACIS Instrument Support - Monthly Progress Report for September 2025


1.  ACIS Characterization

1.3 Monitor scientific on-orbit performance of ACIS

  ...  On September 1 there was a ground commanded radiation shutdown due to elevated ACE soft proton rates from an Earth-directed CME. Shutdown was nominal and saved the focal plane from considerable fluence.

  ...  Continued monitoring of ACIS CTI, gain, trailing pixel pulseheight, detector efficiency, corner pixel distribution, spectral line centroid and width, and focal plane temperature. Updated monitoring web pages.  (http://space.mit.edu/~cgrant/monitor.html).


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.  Engineering trending over the past 60 days is nominal.

  ...  The EEPROM checksum was verified in the SEP0825B loads. Will continue to run monthly.  MIT telemetry processing will automatically check the results and send out an alert if the checksum is unexpected.

  ...  Continued weekly physical audit of the ACIS Engineering Unit lab. All weekly audits were nominal. 

2.2 Flight software maintenance

  ...  ACIS flight software patch H-K-L uploaded on August 15, 2025. First new patch set since September 2023.
  
   ...  We continue to monitor threshold crossing rates.  The current set of TXing parameters were uploaded on Aug 15, 2025.  New commands were required for TXings revC but the rate limits are nearly the same as used previously, uploaded on Oct 20, 2024.

  ...  Collaborated with MKI IT to migrate acis.mit.edu, the last ACIS Solaris machine, to Linux hardware. Completed feasibility study to extend the original ACIS documentation tools beyond hardware retirement. Successfully ran a SunOS 4 image on a QEMU emulation of a SPARCstation 5 on both a Linux VM host and a MacBook Pro host. Successfully ran the FrameMaker license manager and FrameMaker itself on the emulated SPARCstation 5.

2.3 Instrument science performance

  ...  Continued daily quick-look processing of ACIS telemetry and maintained web interface to ACIS real-time data. Updated TXings plot generation software to distinguish revision levels.

  ...  Further documentation of the MIT telemetry pipeline.  Released a draft document describing the TXings plotting software.  Began a draft document describing EGSE network security.

  ...  Continued to publish the "annotated DOT" timeline reports.


3.  CXC Support

3.1 Provide user support

  ...  ACIS memo listing calibration ObsIDs and observation characteristics (ACIS Memo #165) will no longer be updated.  Functionality is replaced by web page (http://acisweb.mit.edu/asc/evt-page.html), which provides the same information but is more automated.

  ...  Answered CXC Cal question about ER ObsIDs that are not ECS observations.

  ...  Answered user question about MIT CCD model used early in the mission.

  ...  Provided CDO with a double-check of radiation shutdown counts for the Chandra newsletter.

3.2 Provide data analysis support

  ...  Participated in CXC Cal/Ops response discussion group.

  ...  Continued to maintain ACIS calibration database of ground and flight data products.


4.  OCC Support

4.1 Use of MIT/ACIS EGSE at OCC

  ...  Continued support and maintenance of ACIS EGSE software and hardware at the Wayside OCC.  Restarted both EGSE machines routinely. 

4.2 Generation of commands for ACIS observations

  ...  Reviewed CXC DS 10.14.2 ECR for any impact on the ACIS operations team.

  ...  Continued working with USINT to verify or update parameters for the cycle 27 problematic ACIS configurations. The initial list had 108 ObsIDs from 11 programs, which is now down to 79 ObsIDs from 7 programs.

  ...  Advised USINT on recommendations for dither parameters with subarrays, and choice of ACIS-I vs ACIS-S for background sensitive observations.

  ...  Reviewed guidelines for checking bright X-ray sources.

  ...  Reviewed FOT Radiation Safing guideline changes.

  ...  Reviewed SEP1025A and SEP1525A command loads; SEP1025 and SEP1525 final OR lists; SEP1025 and SEP1525 preliminary schedules; and SEP1525, SEP1025, SEP2925 LTS OR lists. 

  ...  Checking on automated processes associated with SACGS.