ACIS Instrument Support - Monthly Progress Report for August 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

  ...  Investigated the use by ACIS of the suspect HRC capacitor: M39014/02-1419.  ACIS uses one on each of the FEP boards.  A failure of one of these parts would cause that single FEP to become unusable.

  ...  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 AUG0921A load.   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. 

2.2 Flight software maintenance

  ...  There were two occurrences where next-in-line event histogram data were taken back-to-back with an intervening thermally motivted FEP power down command.  In both cases the second run did not recompute a new bias.  This was a mistake in commanding but also revealed a potential issue with the bias map recalculation logic in the BEP, as the BEP should have automatically recognized that it needed to recompute those bias maps.  Opened ACIS problem report M21081801, "FEP Power Cycle Anomaly".

  ...  Continued work documenting new bias error.  Finalized report on the bias anomaly, "The Bias Map Anomaly in OBSID 24597 (v 1.1)" (https://acisweb.mit.edu/pub/biasanom.24597-v1.1.pdf).

  ...  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.

  ...  A very bright source observed with the HETG nearly triggered a radiation shutdown in July.  In this case, event collection started before the final move to put the target at the aimpoint, so it looked to the BEP like a rapid increase in threshold crossings due to a radiation events.  We are considering operational changes for known bright sources to protect against spurious radiation triggers.

  ...  Continued work on QEMU ACIS emulator development. Fixed bug with BEP-FEP shared memory interface, introduced when page-aligned interface size on FEP side (a portability change).  Installed and tested ACIS QEMU build 24.

  ...  Published new version of the ACIS Flight Software User's Guide including a general rewrite of the "example scenarios" to better match the reality of running ACIS rather than what was expected pre-launch.
  
2.3 Instrument science performance

  ...  Participated in monthly ACIS operations meetings.  Discussed ObsID 24597 bias anomaly, the use of problematic MLCC in ACIS, and the status of expanded use of the SPM.  ACIS is comfortable with the allowed range of roll angles.

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

  ...  Repaired a 1-bit error in a bias packet for ObsID 46165.  This is a known problem when a single bit flip occurs in a Huffman-compressed ACIS bias map, and a standard procedure exists for fixing it and repairing the original EHS file.  At the same time, repaired similar bit flips in earlier bias maps, as requested by DSOps.

  ...  The LETG insertion anomaly was the first time the new version of SCS106, the science instrument safing commanding, was run.  The new version powers on three FEPs to keep the electronics warmer during extended downtime and ran correctly.

  ...  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.

3.2 Provide data analysis support

  ...  Answered CXC calibration scientist questions on less-standard archival data, specifically alternating exposure mode and an interrupted ObsID.

  ...  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 and again after FST network maintenance.

  ...  Assisted with setting up for a future backup OCC data flow test.

4.2 Generation of commands for ACIS observations

  ...  Assigned SI modes to most of the GO and GTO ACIS observations in cycle 23.  USINT has been informed of the remaining ACIS configurations that have issues to be addressed before assignment.

  ...  Built, tested, and deployed three new SI modes for calibration observations of Cas A

  ...  Reviewed AUG0921A and AUG0221T command loads, AUG0921, and AUG1621 final OR lists, AUG0921 and AUG1621 preliminary schedules, and AUG2321 LTS OR list.

  ...  Assigned 3 SI modes. Dropped chips from 14 ObsIDs

  ...  Checking on automated processes associated with SACGS.