ACIS Instrument Support - Monthly Progress Report for December 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. 

       * CL32-33, 1 successful run 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 shows that while precursors at all distances contribute to CTI differences, only the closest precursors (within 100 pixels) significantly degrade spectral resolution.

  ...  Continued lab testing of radiation damaged CCD shows a fat zero from optical light can be used to fill traps and improve CTI and FWHM.  As the fat zero level increases, both CTI and FWHM continue to improve until the random noise associated with the fat zero dominates the FWHM.  The CTI continues to improve up to 200 electrons.

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.  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 however decrease in telemetry saturation was deemed insufficient to change standard operations.

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 some correlation to S3 amp_rej rates in quiescence, plus irregular flaring.  The flaring behavior is supressed when ACIS is not in the focal plane, so soft protons may cause the flares.  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

 [...] Participated in ACIS telecon

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.


Outreach:

"Chandra Observations and Mass Distribution
of EMSS1358+6245", by M. Bautz, J. Arabadjis and G. Garmire, talk at the
"New Visions of the X-ray Universe in the XMM-Newton and
Chandra Era" conference, 26-30 November 2001, Nordwijk, The Netherlands