ACIS Instrument Support - Monthly Progress Report for July 2000


1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continued quantum efficiency calibration of radiation damaged CCD, w457c1.  Final results will be used to characterize the uniformity of CCD QE after radiation damage.

  ...  Conducted tests in the command load for the 16-row squeegee mode with no initial flushing frames.  Bias frames will be used to measure trap time constants.  Results indicate less initial charge than expected - analysis on-going.

       * 24 July - Ran 16-row squeegee with no initial flush frames on flight device S0 (L5, ObsID 61987)
       * 27 July - Ran 16-row squeegee with no initial flush frames on flight deivce S2 (L6, ObsID 61985)


1.2 Define and characterize alternative CCD readout modes

  ...  Conducted real-time tests of squeegee readout mode on flight device S0.

       * 13 July - ran "maximum observing efficiency" squeegee mode with 2-row squeegee, 2x2 on-chip summation and normal speed readout (R7, ObsID 62876)

  ...  Conducted tests of squeegee mode on flight device I0 in the command load.
       * 01 July - ran "maximum angular resolution" squeegee mode with 2-row squeegee and 8 times slower readout (L4, ObsID 62007)
       * 30 July - ran "maximum observing efficiency" squeegee mode with 2-row squeegee, 2x2 on-chip summation and normal speed readout (L7, ObsID 61981)

  ...   Analysis of flight squeegee results on-going.  Preliminary results can be found at http://space.mit.edu/~cgrant/squeegee/squeegee.html.  Results for both S0 and I0 are as expected based on lab results.

  ...  Continued lab testing of squeegee readout mode using w459c1.

  * The column to column CTI performance differences of the lab damaged CCD, w459c1, remains stable over months and over dozens of temperature cycles at energies of C-K, N-K and O-K.  The correct gain correction seems to be described by the sqrt(q) volume occupied by charge q.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued monitoring of ACIS CTI.  Searched for increase in CTI associated with strong solar activity in mid-July.  No detectable increase found.

1.4 Update and improve CCD simulation

  ...  Continued recalibration of S3 QE using sub-assembly and XRCF data and more accurate source/detector models.

  ...  Continued effort to model the volume occupied by a charge packet as a function of signal charge in the CCD pixels.  The CCD model and the flight software CTI corrector requires this relationship for accurate results.

 [...  Started work on introducing FI CCD CTI effects in the CCD model.

 [...] Submitted new QE curves with higher energy resolution for submission to CXC Calibration Group.  Higher energy resolution QE data across absorption edges required for accurate gratings data analysis.


2. Engineering

2.1 Flight software maintenance

  ...  Continued to investigate the "FEP T-Plane Latch-Up" anomaly (ACIS s/w problem report #133).

 [...] Analyzed an anomaly in OBSID 1701 that resulted from a misunderstood flight s/w feature; submitted additions to the ACIS Command Ruleset to prevent the anomaly from recurring.

2.2 Instrument science performance

  ...  Continued quick-look processing of all ACIS science runs, using EHS telemetry supplied by the GOT.

  ...  Continued to publish the "annotated DOT" timeline reports.

  ...  Continued testing of flight S/W algorithms to estimate correction for charge lost to medium time-constant CCD charge traps.

  ...  Assisted in upgrading the ACIS engineering unit.

2.5 Participate in Chandra activities

 [...] Supported squeegee readout mode tests on 01 July, 13 July, 24 July, 27 July and 30 July including load and CAP review and real-time data analysis support.

 [...] Supported real-time monitoring of radiation levels and instrument performance during and after the strong and unusually hard solar storm in mid-July.  

3. CXC Support

3.1 Provide user support

  ...  Continued to assist the CXC MTA in CTI monitoring and background correlations.  Worked with software designers to improve accuracy of CTI results.

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

3.2 Provide data analysis support

 [...] Revised several sections of "ACIS Telemetry Products: Level 0 to CXC Archive ICD".

 [...] Attended meetings with CXCDS staff to clarify the meaning and use of FITS keywords in Level 0 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.


Outreach:

"Review of X-ray CCDs" at the NASA Space Astrophysics Detector Meeting (6/28/00, Space Telescope Science Institute)

"The Advanced CCD Imaging Spectrometer" to an audience of high school science teachers, sponsored by the Wright Center for Science Education (7/21/00, MIT)