ACIS Instrument Support - Monthly Progress Report for July 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

  ...  Reviewed ACIS parts list and documentation to verify whether the MLCC capacitor highlighted by the HRC anomaly investigation is in use on ACIS.  Draft memo released showing that there is one of this type of capacitor on each of the FEP boards.

  ...  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 JUL0521A 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

  ...  Continued work documenting new bias error.  Published new memo "The Bias Map Anomaly in OBSID 24597 (v 1.1)" (https://acisweb.mit.edu/pub/biasanom.24597-v1.1.pdf).  This memo includes a description of the anomaly itself, analysis of the anomlous bias map, a detailed look into the algorithm used to create bias maps, posits a root cause of the anomaly (excess charge in the first two rows of the initial overclocks), and a complete search for the same or related anomalies in the full mission history.  This particular bias anomaly is unique, and a similar anomaly occurred once in a raw data frame.  While a FSW patch could eliminate this problem, the effort may not be warranted for such a rare event.

  ...  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.  Prototyped patches to the GNU Debugger (GDB) Version 7.10 to work with the QEMU GDB server and ACIS ECOFF files.  Determined that GDB watchpoints are insufficient to detect reads from uninitialized memory.

  ...  Published new version of the ACIS Flight Software User's Guide including corrections and suggestions from the full ACIS team.

  ...  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.

  ...  Reviewed USINT letters to the observer for cycle 23.

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 calibrated time dependent gain and contamination updates.

  ...  Participated in Thermal Working Group meeting discussion of allowing ACIS observations to go below the nominal focal plane temperature of -119.7C (i.e. changing the heater set point).  Not yet obvious if this would help MP scheduling.  Do not have calibration data for these temperatures.

  ...  Participated in planning telecon for upcoming IACHEC meeting.  Postponed again from September 2021 to May 2022.

  ...  Contributed to upcoming IACHEC newsletter as chair of Detectors and Background Working 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.

4.2 Generation of commands for ACIS observations

  ...  Verified with the Engineering Unit two new power commands for thermal testing. Installed in the ODB.

  ...  Began discussion about ways to power up more FEPs for observations with one CCD active when DPA temepratures are predicted to be low.  Would require many new SI modes, and software changes for both ACIS and FOT MP.

  ...  Reviewed JUL0821A and JUL1221A command loads, JUL0821, JUL1221, and JUL1921 final OR lists, JUL0821 and JUL1921 preliminary schedules, and JUL1921 and JUL2621 LTS OR lists.

  ...  Dropped chips from 4 ObsIDs

  ...  Checking on automated processes associated with SACGS.