ACIS Instrument Support - Monthly Progress Report for February 2002

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. 

       * CL38-40, 3 successful runs of no-squeegee cuckoo clocking on I3 Node 3

  ...  Continued analysis of no-squeegee cuckoo data.  Work continues on defining filters and corrections factors that would improve over-all performance.  Tested two pulseheight correction algorithms, one based on the distance to the first precursor, the second a more complicated sum of precursor pulseheights and distances which produces some improvement in spectral resolution.

  ...  Continued lab testing of radiation damaged CCD on fat zero approaches.  CTI improves whether the fat zero is produced from optical light or "anomalous dark current".  

1.2 Design and characterize alternative CCD readout modes

  ...  Continued study of charge injection to measure CTI using ACIS electronics in the lab. Verified flight SRAM/PRAM.  Will be tested on flight instrument in mid-March.
 
1.3 Monitor scientific on-orbit performance of ACIS

 [...  Analyzed E0102 and ExtCalSrc data to search for putative QE decrease at low energies.  Data are suggestive of a long-term slowly increasing layer of contamination on ACIS, but other influences, such as CTI and particle background rates, cannot yet be ruled out.  Analysis ongoing.

  ...]  Completed analysis of fifth CTI measurement in alternating exposure mode with frame times of 4.0 and 3.2 seconds (ObsID 61327, 31 Jan).  Results from this test are consistent with previous alternating exposure mode tests.  Derived CTI degradation is also consistent.  (see http://space.mit.edu/~cgrant/cti/altexp.html)

  ...  Continued monitoring of ACIS CTI.  No significant changes detected. Updated CTI web page (http://space.mit.edu/~cgrant/cti/)

1.4 Update and improve CCD simulation

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

  ...  Reanalyzing HIREFS calibration data of S3 to compare to CCD simulator output and to better understand gain function at very low energies.

 [...  Verifying that CTI simulator produces similar low energy tails to real data.  Ongoing.


2. Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.

2.2 Instrument science performance

  ...  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

2.3 Participate in Chandra activities

 [...  Supported preparation of CAP #785 - a test of charge injection on S0 to be run in mid-March.


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.

  ...  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 OCC.