ACIS Instrument Support - Monthly Progress Report for April-June 2025


1.  ACIS Characterization

1.3 Monitor scientific on-orbit performance of ACIS

  ...  On June 1 there was an autonomous radiation shutdown due to TXings from an Earth-directed CME after an M8 flare.  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).

  ...  Prepared slides for and presented ACIS status at Chandra Quarterly in May.


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 APR0725A, MAY0525A, and JUN0925A 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. Weekly audits were nominal. 

2.2 Flight software maintenance

  ...  ACIS flight software patch H-J-K uploaded on September 19, 2023.  First new patch set since August 2022.

  ...  ACIS flight software patch HKL continues to progress towards uplink.  Patch contends presented to and approved by the Chandra FSW WG on May 21.  Patch and uplink products were presented and approved at Chandra Flight Directors Board on June 26.  Uplink scheduled for August 15.

   ...  We continue to monitor threshold crossing rates.  The current set of TXing parameters were uploaded on Oct 20, 2024.

  ...  Discussion of TXing parameter choice "philosophy" settled on following recommendations in the rev C TXings ECO.  Selected initial set of parameters for command library, plus auxiliary "dump" and "quiet" commands.  Commands built and tested on EU and QEMU, installed in the ACIS tables ODB.  Final selection of parameter uplink command will be made closer to August 15.

2.3 Instrument science performance

  ...  Participated in monthly ACIS operations meetings.  Discussed TXing trigger during bright source observation, status of FSW patch development, ACIS calibration issues, and the data loss on DOY 2025:163.

  ...  Continued daily quick-look processing of ACIS telemetry and maintained web interface to ACIS real-time data.  Adjusted processing for DSS-65 data loss on DOY 163.

  ...  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.

3.2 Provide data analysis support

  ...  Assisted CXC arcops with 1-bit data corruption in ObsID 30878.

  ...  Investigated reported from FOT LSE of science data loss during ObsID 30930.  MIT pipeline confirmed ACIS was functioning nominally and reported all data from the science run.  Problem was found to be a V&V software issue.

  ...  Participated in CXC Cal/Ops response discussion group.  (Re)distributed 2006 Project Science study on Chandra orbit evolution and the radiation belt environment.  Recent low perigee dipped into lower radiation belts populated by harder particles which could contribute to gain calibration changes.  Discussed updates to contamination calibration.

  ...  Technical reviewer for HST/CXO joint proposals.

  ...  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.   Updated EGSE software to recognize TXings Rev C structures.

4.2 Generation of commands for ACIS observations

  ...  Finished up some lingering cycle 26 configuration issues.  All ACIS ObsIDs now have SI modes and all chip drop configurations map to existing SI modes.

  ...  Supported a meeting between ACIS ops and HETG USINT to ensure that all parties understand the TXings false trigger on March 24 by a bright HETG source, and how to prevent a reoccurrence.

  ...  Compiled and submitted test plan and completed testing of ACIS command generation and downlink monitoring tools with CXC DS10.14.  Submitted test report.

  ...  Reviewed APR1425A, MAY1225A, MAY1225T, JUN1625A command loads; APR1425, MAY1225, JUN1625 final OR lists; APR1425, MAY1225, MAY1225T, JUN1625 preliminary schedules; and APR2825, MAY2625, JUN3025 LTS OR lists.

  ...  Checking on automated processes associated with SACGS.