ACIS Instrument Support - Monthly Progress Report for January-March 2022

1.  ACIS Characterization

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Autonomous radiation shutdown on March 28 instigated by the ACIS txings monitor due to prompt radiation from M4 flare.  This was the fourth ACIS initiated radiation shutdown since the patch was activated in 2012.

  ...  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).

  ...  Presented poster at the March HEAD meeting, examining the correlation between the quiescent particle background measured on ACIS and that by the AMS particle experiment on the ISS.

  ...  Submitted abstract to the 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"

  ...  Conducted a thermal test in January.  In this test, the ACIS focal plane temperature heater set point was set to -126C. Chandra moved to a forward-Sun attitude to allow the focal plane to cool below the nominal set point of -120C, then moved to a tail-Sun attitude to see how fast the temperature rises.  The goal was to determine if permitting lower ACIS operating temperatures would offer any dwell-time benefit for mission planning.  The result was that benefit would be very small.

 
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 JAN1022A, FEB0722A, MAR0722A 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. Multiple instances os issues requiring reboots.

  ...  Responded to FOT request to change yellow/red low limits for 1DP28[A|B]VO and 1DE28[A|B]VO, the +28V input voltage for the DPA and DEA, as these limits will be increasingly violated heading toward low perigee.  Limit violations are understood and limits were changed in January.

  ...  Provided FOT with pre-launch documents on the ACIS External Calibration Source.

2.2 Flight software maintenance

  ...  The ACIS BEP reported a fatal bus error and had a watchdog reboot into FSW v=11 on January 15.  A total of 240 ksec of observing time was lost.  Ran CAP1597 to verify the patches were still in memory and warmboot to return to FSW v=56. This is the 7th bus error since launch, and one of 3 that remain unexplained due to lack of diagnostic data.  (http://acisweb.mit.edu/pub/buserr-25741-v1.1.pdf)

  ...  After watchdog reboot, fixed and updated email and text alert lists.

  ...  On March 23, there was an apparent re-appearance of a FEP thresholding anomaly (a t-plane latchup). The anomaly was cleared by the routine power-cycle before the next observation.  (https://acisweb.mit.edu/pub/acis-tplane-24760-v1.0.pdf)

  ...  New ACIS flight software patch that preserves BEP register values, mostfatal, has been developed and tested, but is on hold in favor of work on the improved txings patch. This patch would provide more diagnostic information after a fatal bus error, such as on January 15.

  ...  New ACIS flight software patch, fepbiasrec has been written and tested, but is currently on hold in favor of work on the improved txings patch. This patch forces the FEP to recompute its bias map after being power-cycled, to prevent the anomaly that occurred summer 2021 with consecutive event histogram runs.

  ...  Exploring improvements to the ACIS radiation monitor, txings, with the goal of improving the sensitivity of radiation triggering. Organized txings WG. New version of txings with additional test of rate behavior incorporated into ACIS flight software patch level standard G, optional I, configuration J.

  ...  ACIS Flight Software Patch G-I-J released for team review. Includes an improved txing rev B (https://acisweb.mit.edu/pub/ACIS_Patch_G-I-J.pdf)

  ...  Working on parameter optimization for txing rev B.  Default parameters installed within the patch and optimal parameters for the upload and beyond will need to be determined.

  ...  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. Threshold crossing rates have been decreasing, indicating the transition from solar minimum to solar maximum. The TXING parameters were updated on March 29 to better match the current quiescent rates.

  ...  Completed team review of ACIS Flight Software User's Guide.  Final updated version released Feb 14, 2022.

2.3 Instrument science performance

  ...  Supported response to the HRC side-B electronics anomaly and ACIS return-to-science without HRC discussions. Short-term radiation mitigation action include inserting the HETG during radiation belts, a RadMon deadman to ensure ACIS is safe before rad belts, and requiring at least one FI CCD for all observations to improve txings radiation detection.  Longer term actions include improvements to the txings algorithm already underway.

  ...  Participated in monthly ACIS operations meeting. Discussed watchdog reboot, FP heating/cooling test, ACIS response to HRC anomaly, and improvements to txings.

  ...  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

  ...  Reviewed ACIS section of senior review report.  Provided slides on txings and bakeout decision for the senior review presentation.

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

  ...  Participated in CXC Cal/Ops ACIS response discussion group.  Discussed plans for raising focal plane temperature limits, results from the focal plane cooling/heating test including performance below -120C, and other calibration issues.

  ...  Participated in planning telecon for upcoming IACHEC meeting. In-person meeting cancelled and replaced by virtual meeting.  Organizing a session on background measurement and modeling. 

  ...  Discussed CTI calibration and software mitigation with CXC SDS persons.

  ...  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 documentation on remote use of ACIS EGSE. Ran training session with ACIS ops.

4.2 Generation of commands for ACIS observations

  ...  Worked with USINT to change all ACIS configurations to always include at least one required FI CCD for better txings radiation monitoring.

  ...  Confirmed that CXCDS 10.10.2.3 has no impact for ACIS, so no testing was required.

  ...  Prepared internal presentation on potential plan to turn on additional FEPs during 1-CCD observations for thermal reasons.  In response to the HRC anomaly, 1-CCD observations are much less likely, so this plan has been shelved.

  ...  Reviewed FSDS/Jira ticket on proposed changes to OR lists.

  ...  Updated SI mode assignment documentation to include recent changes.

  ...  Reviewed JAN1722A, JAN2422T, FEB1422A, APR0122, and APR0322 command loads, JAN1722, JAN1822, JAN2422, FEB1422 APR0422, APR0122, and APR0322 final OR lists, JAN1722, JAN1822, JAN2422, FEB1422 APR0122, APR0322 preliminary schedules, and DEC3122, FEB2822, FEB2122, APR1822 LTS OR lists.

  ...  Assigned 51 SI modes. Dropped chips from 55 ObsIDs

  ...  Built a new SI mode to add an FI CCD to an S3 only run.

  ...  Checking on automated processes associated with SACGS.