ACIS Instrument Support - Monthly Progress Report for August - September 2022

1.  ACIS Characterization

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Following Bright Star Hold due to elevated ionizing radiation on August 11, verified ACIS was safe, monitoring housekeeping data during recovery, and supported safing action recovery.

  ...  Following CTU reset on August 19, verified ACIS was safe, monitoring housekeeping data during recovery, and supported safing action recovery.  Ran two CAPs to collect ECS data during recovery, one of which was the longest calibration source measurement in the history of the mission, 140 ksec, adding a substantial amount of both cold and warm time to the calibration database.

  ...  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).

  ...  Submitted proceedings paper for SPIE Astronomical Telescope + Instrumentation on the ACIS background correlation with AMS.  "Towards precision particle background estimation for future X-ray missions: correlated variability between Chandra ACIS and AMS".  (http://arxiv.org/abs/2208.01130)

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.

  ...  Engineering team responded on the advisability of using the focal plane bakeout heater for the warm (-105C) calibration observations, to speed up the temperature rise.  Heater has not been used in nine years.  No reason to expect failure, but a failure mode would require a switch to DEA-B, which is not trivial.  Decided to stick with standard heater for less risk.

  ...  The EEPROM checksum was verified in the AUG0822A and SEP0522A loads. Will continue to run monthly.  MIT telemetry processing will automatically check the results and send out an alert if the checksum is unexpected.

  ...  Clarified with FOT the timing of the EEPROM check commands and interaction with other ACIS commanding.

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

2.2 Flight software maintenance

  ...  A previously unknown bug in FEP flight software was discovered on September 19, during ObsID 25140, which caused a complete loss of all data for that observation.  FEP bug can only affect timed exposure runs in alternating exposure mode, and even then only for a small set of parameters.  A FSW patch which eliminates this bug, "biasphase3", is under development.  In the meantime, observers are recommended to avoid alternating exposure mode.  (Only 18 runs in the past decade and none since 2018.)
Documented in report "ObsID 25140 Anomaly Investigation" (https://acisweb.mit.edu/pub/acis-25140-anomaly-v1.0.pdf)

  ...  ACIS flight software patch G-I-J (improved TXings) uploaded on August 11, 2022.  First new patch set since January 2020.  No issues to date.

  ...  Final preparation and review of CAPs to upload FSW patch and update TXing parameters to the optimal values for August 2022. "CAP1621: Uplink of ACIS Flight SW Standard G, Optional I with SOP_ACIS_SW_STDGOPTI.doc" and "CAP1622: Update TXINGS Parameter Values". (https://acisweb.mit.edu/asc/cap/CAP1621.pdf and https://acisweb.mit.edu/asc/cap/CAP1622.pdf)

  ...  Real-time in person and remote support for ACIS FSW uplink activity.  Verified instrument status, command echos, and the contents of the FSW patch dumps and TXing parameter dumps.

  ...  Changed science telemetry alert settings to the new FSW patch v=58.

  ...  Updated internal documentation to reflect the new FSW patch level.

  ...  TXing rev B parameter optimization WG produced and reviewed memo on txings parameter update process. "Monitoring ACIS Background Rates for the TXings Patch" (https://acisweb.mit.edu/pub/acis-txings-monitoring-v1.0.pdf)  Web page updated monthly to determine when new parameters are necessary. Developed script to streamline testing of TXings parameter updates.

  ...  We continue to monitor threshold crossing rates. Threshold crossing rates have been decreasing, indicating the transition from solar minimum to solar maximum. The TXing revB parameters were updated on August 11, 2022 and September 12, 2022.  Reviewed/verified CLD files for new TXing parameters.

  ...  Continued work on QEMU ACIS emulator development.
       - debugged shared memory issue when running under Darwin
       - started examining QEMU shutdown process to enable cleanup of Darwin shared memory sections
       - resolved QEMU shutdown process to execute a cleanup of Darwin shared memory sections
       - started looking at run-time modification of the "throttle" start-up parameter that changes the emulated CPU speed
		

2.3 Instrument science performance

  ...  Participated in monthly ACIS operations meeting. Discussed the status of the new FSW patch load and whether new txing parameters were needed, new FEP anomaly, problems with Chandra alerts, and strategy for development of the next three ACIS FSW patches.

  ...  Installed updates to science telemetry monitoring software running at SAO.

  ...  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

  ...  Answered user question on cosmic ray blooms and where to find ACIS raw images.

  ...  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

  ...  Participated in CXC Cal/Ops ACIS response discussion group. Discussed cold ECS time, gain calibration, contamination measurements, plans for AO-24 and the new default dither parameters, plans for warm -105C calibration observations, and possible PSF changes.

  ...  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

  ...  Assigned ACIS SI modes to cycle 24 observations. Notified USINT of configurations with obvious problems that require changes.

  ...  Submitted ACIS test plan for CXC DS10.11.1.  Completed testing and submitted test report.

  ...  Built, tested, and installed new focal plane temperature command for calibration observations at -105C.  Reviewed SAR for testing of -105C temperature command and SAR for insertion of commands into OCT1022 and OCT1722.

  ...  Built, tested, and installed new SI mode for calibration observation of GX 3+1.

  ...  Diagnosed problem with mission planning CCT SI mode table. Reviewed updated version.

  ...  Participated in discussion on changing the ACIS default dither to improve ACA performance.  Discussions about implementation, interaction with ACIS SI modes and timing of cycle 24 assignment. Confirmed that dither change should not have any impact on optimal bias algorithm parameters.

  ...  Began work on new NIL event histogram modes to support HRC return-to science.  New modes will use fewer CCDs, to allow for TXings radiation monitoring while minimizing thermal impact on HRC.

  ...  Reviewed ACIS load review software changes.

  ...  Reviewed AUG2222A, AUG2122A, SEP1922 command loads; AUG2222, AUG2122, SEP1922 (x2) final OR lists; AUG2222, AUG2122, SEP1922 (x2) preliminary schedules; and SEP0522, SEP1922, OCT0322, SEP2622, OCT0322 LTS OR lists.
 
  ...  Assigned 20 SI modes. Dropped chips from 10 ObsIDs

  ...  Checking on automated processes associated with SACGS.