ACIS Instrument Support - Monthly Progress Report for June 2021

1.  ACIS Characterization

1.3 Monitor scientific on-orbit performance of ACIS

  ...  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 indicate a stable environment.

  ...  The EEPROM checksum was verified in the JUN0721A load.   Will continue to run monthly.  MIT telemetry processing will automatically check the results and send out an alert if the checksum is unexpected.

  ...  Reviewed Flight Note 611, expanding the use of the Sun Position Monitor, in particular the limits placed on pitch/roll by the ACIS radiator shades.  Reviewed pre-launch studies and emails.

  ...  Continued weekly physical audit of the ACIS Engineering Unit lab. 

2.2 Flight software maintenance

...  There was a new bias anomaly during ObsID 24597.  Due to this anomaly, most of the valid data from one quadrant of S4 was rejected on-board.  This was a calibration observation and that quadrant would not have contained useful data.  We believe the root cause of the anomaly is excess charge in the read out at precisely the wrong time in the bias determination process.  This is the first occurrence of this particular anomaly in the mission, and given the low probability of it reoccurring, we do not currently have plans for any mitigation.  Opened problem report M21062101 (https://acisweb.mit.edu/axaf/spr/prob0156.html).

  ...  ACIS flight software patch G-H-I (improved buscrash and new deahktrip) uploaded on January 24, 2020.  First new patch set since June 2014.  No issues to date.

  ...  We continue to monitor threshold crossing rates.  The current TXINGS parameters were last updated on July 28, 2016.  Threshold crossing rates have flattened out and started decreasing, indicating the end of solar minimum. We anticipate needing to lower the trigger threshold in the next year as rates continue to drop and activity increases.

  ...  Continued work on QEMU ACIS emulator development.  Researched techniques to detect reads of uninitialized memory to support patch development.  Started GNU Debugger symbol table issues when running on the QEMU emulator using a 64-bit host
 
  ...  Continued team review of ACIS Flight Software User's Guide. Reviewed sections on example scenarios.
  
2.3 Instrument science performance

  ...  Participated in monthly ACIS operations meetings.  Discussed roll angle limitations imposed by the ACIS radiator and the new ACIS bias anomaly.

  ...  Completed reviews and final approval for patch to SCS106, the ACIS instrument safing command sequence.  The patch changes the power down command to leave three FEPs on, which keeps the electronics from getting too cold during long safing actions.

  ...  Continued daily quick-look processing of ACIS telemetry and maintained Web interface to ACIS real-time data.  

  ...  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 new web page (http://acis.mit.edu/asc/evt-page.html), which provides the same information but is more automated.

  ...  Served as technical support during Chandra proposal review.

  ...  Working with USINT to configure proposed TOO to make use of existing SI modes.

  ...  Answered user question about provis and target visibility.

3.2 Provide data analysis support

  ...  Participated in CXC Cal/Ops ACIS response discussion group.  Discussed PCA method for fitting ECS and Cas A data to calibration time dependent gain and contamination updates.

  ...  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.  Completed scheduled restart of both EGSE telemetry processing.

4.2 Generation of commands for ACIS observations

  ...  Completed ACIS testing of CXCDS 10.10, including SACGS, load review scripts, and the MIT processing pipeline.  Submitted test report.

  ...  Reported erroneous blanking of ACIS SI mode in the OCAT for two observed ObsIDs by arcops during CXCDS 10.10 installation.  Fixed by arcops.

  ...  Built and reviewed two new power commands for thermal testing.

  ...  Reviewed JUN0721A command load, JUN0721 final OR list, JUN0721 preliminary schedule, and JUN0721 and JUN2121 LTS OR lists.

  ...  Assigned 3 SI modes. Dropped chips from 2 ObsIDs

  ...  Checking on automated processes associated with SACGS.