ACIS Instrument Support - Monthly Progress Report for November 2001

1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continued collection of raw data in "cuckoo" clocking mode which allows for more efficient telemetry of raw data. 

       * CL29-31, 2 successful runs of no-squeegee cuckoo clocking on I3 Node 3 (focal plane temperature too warm for one run)

  ...  Continued analysis of no-squeegee cuckoo data.  Sacrificial charge analysis has yielded parameters for the longest time constant trap (t~seconds).  Results are consistent with the improvement in CTI seen with squeegee mode (which fills these traps).

 [...] Lab testing of radiation damaged CCD shows a fat zero from optical light can be used to fill traps.

1.2 Design and characterize alternative CCD readout modes

  ...  Continued study of charge injection to measure CTI using ACIS electronics in the lab.  Flight version of SRAM/PRAM for sacrificial charge measure of CTI is ready for final testing and is setup to measure CTI near the Al-K line..

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued monitoring of ACIS CTI.  Three radiation events required SI safing (SCS 107).  No significant changes detected. Updated CTI web page (http://space.mit.edu/~cgrant/cti/cti120.html)

  ...  Continued study of ACIS background, both quiescent and flares, for multiple SIM and grating positions.

 [...] Investigated affect of lowering upper amplitude threshold on CTI detrending which would decrease telemetry saturation during CTI runs.  Detrending is unaffected.

1.4 Update and improve CCD simulation

  ...  Continued work on detailed physical model of FI CCD including CTI and sacrificial charge.


2. Engineering

2.1 Flight software maintenance

 [...  Investigation of ACIS t-plane latchup anomaly which took place on Oct. 29 and November 4.  This is the second and third occurence since launch (first was June 27, 2000).  During real-time contact dumped ACIS memory and warm booted.  No reoccurances of anomaly to date.  Analysis ongoing.

2.2 Instrument hardware engineering performance

  ...  Continued to monitor hardware operations.  No problems.

2.3 Instrument science performance

 [...  Investigated anomalously high count rate on S4 CCD during ObsID 1585 on November 19.  High count rate due to increase in "streaking" along rows.  Analysis of streak frequency with time shows no correlation with electronics or focal plane temperature, some correlation with S3 amp_rej rates which measure the high energy particle background.  Ringing pattern of streaks along rows is uncorrelated with bias ringing and not symmetric about readout nodes.  Analysis ongoing.

  ...  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.

  ...  Continued to develop flight s/w algorithms to implement "Squeegee" clocking mode and to report precursor charge from ACIS CCDs.

 [...] Participated in ACIS operations meetings

2.4 Participate in Chandra Activities

 [...] Supported real-time activities during ACIS t-plane latchup anomaly including CAP review, commanding checking and real-time data analysis

3. CXC Support

3.1 Provide user support

  ...  Updated ACIS memo listing calibration ObsIDs and observation characteristics (ACIS Memo #165).

3.2 Provide data analysis support

  ...  Participated in CXC Cal/Ops RMF discussion group.

 [...] Supported testing of CTI correction option in acis_process_events.

4. OCC Support

4.1 Use of MIT/ACIS EGSE at OCC

  ...  Continued support and maintenance of ACIS EGSE software and hardware at the OCC.