ACIS Instrument Support - Monthly Progress Report for June 2000


1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

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

 [...] Analyzed dynamics of charge accumulation and dissipation in squeegee rows.  It was shown that from squeegee bias frame, trap time constants can be extracted.  A model has been developed to implement such analysis.  Electron time constants were determined for flight chips S0 and I0.  Similar analysis was performed on the data acquired from the ground irradiated chip w459c1.  The results are described in ACIS memos #187 and 189.

 [...  Began quantum efficiency calibration of radiation damaged CCD, w457c1.  One quantum efficiency scan complete for lines of O, Cl, Al Mn, Cu and Ti.  Final results will be used to characterize the uniformity of CCD QE after radiation damage.

1.2 Define and characterize alternative CCD readout modes

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

       * 09 June - ran "maximum spectral resolution" squeegee mode with 16-row squeegee, 2x2 on-chip summation and 8 times slower readout (Squeegee V, R5).

       * 15 June - ran "maximum angular resolution" squeegee mode with 2-row squeegee and 8 times slower readout (Squeegee VI, R6).

  ...  Conducted tests of squeegee mode on flight device I0 in the command load.

       * 21 June - ran "maximum spectral resolution" squeegee mode (L2)

       * 26 June - ran bias-only 16-row squeegee without initial flushing frames (L3)

  ...   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 ground lab results.

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

       * With regard to the low energy lack of FWHM decrease with squeegee, this was shown to be due to column to column variations. By correcting for column effects the FWHM improves by 20% with squeegee at carbon. The correlation between column at carbon and oxygen is pretty convincing that this is a permanent feature of the radiation damaged CCD.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued occasional monitoring of ACIS CTI.  Searched for increase in CTI associated with strong solar activity in early June.

1.4 Update and improve CCD simulation

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

2. Engineering

2.1 Flight software maintenance

 [...] Prepared ACIS sequencer loads for continuing squeegee tests

  ...  Continued development and testing of squeegee flight s/w patch

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 development of flight S/W patch to estimate correction for medium time-constant CCD charge traps.

  ...  Monitored performance of new ACIS Flight Software patches including FEP bias parity error fix.  FEP bias parity errors never exceeded trigger value.

 [...] Completed a report on the FEP 0 anomaly (OCCcm03148) and delivered to OCC (http://acis.mit.edu/asc/fep0Rept.pdf).

  ...] Completed plans for upgrading the ACIS engineering unit.  Work to commence on July 1.

2.5 Participate in Chandra activities

 [...] Supported squeegee readout mode tests on 09 June, 15 June, 21 June and 26 June including load and CAP review and real-time data analysis support.

 [...] Supported ACIS anomaly investigation and real-time commanding of resolution on 27-28 June (ACIS Problem Report #133, see http://acis.mit.edu/axaf/spr/prob0133.html).

3. CXC Support

3.1 Provide user support

  ...  Continued to assist the CXC MTA in CTI monitoring and background correlations and assisted CXC in implementing detrending of CTI data for particle background correction.

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

 [...] Attended CXC ACIS Working Group meeting at SAO-CfA on 30 June.  Supported discussion of calibration and software issues.

3.2 Provide data analysis support

 [...] Reviewed "ACIS Telemetry Products: Level 0 to CXC Archive ICD", Revision 3.2.

4. OCC Support

4.1 Use of MIT/ACIS EGSE at OCC

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


Outreach:

"Chandra Observations of Lensing Clusters of Galaxies", Invited Talk at AAS meeting, June 8, in Rochester, presented by Mark Bautz


New ACIS Memo:

189 - Squeegee bias on I0, S0 and w459c1

all memos available at http://space.mit.edu/ACIS/iacis.html