ACIS Instrument Support - Monthly Progress Report for November 2000


1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

 [... New ACIS memo describes a simple analytical model for charge loss including sacrificial charge effects (ACIS Memo #193).  Analysis of cosmic ray background from raw mode data using this algorithm is proceeding and is consistent with the degraded spectral resolution observed.  

  ...  Continued collecting 16-row squeegee data in raw mode on I0.  Data analysis will provide information necessary for CTI correction algorithms.  Preliminary analysis of the raw mode data was performed.  Refinement of analysis algorithm is still in progress. 

       * 08 November - (L24, ObsID 61858)
       * 16 November - (L25, ObsID 61852)
       * 18 November - (L26, ObsID 61849)
       * 28 November - (L28, ObsID 61837)

 [...  Began collection of raw data in "cuckoo" clocking mode which allows for more efficient data telemetry.  More cuckoo observations planned for December.

       * 13 November - (R11, ObsID 62872) First functional test of cuckoo clocking on S0.  Successfully completed by real-time commanding.
       * 23 November - (L27, ObsID 61843) First test of cuckoo clocking on I0 in the command load.

1.2 Define and characterize alternative CCD readout modes

  ...  Tested new "cuckoo" clocking mode which packs raw data more efficiently in the FEP to prevent data loss from bottlenecks in the FEP-to-BEP transfer.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued monitoring of ACIS CTI.  Updated MIT CTI web page (http://space.mit.edu/~cgrant/cti/cti120.html) including parallel and serial CTI measurements on S3.

 [...] Presented paper at HEAD meeting on 11 Nov entitled "Monitoring the Charge Transfer Inefficiency of ACIS and the Impact of the Varying Cosmic-Ray Background" (http://space.mit.edu/~cgrant/HEAD00.poster.ps)

 [...] Attended XMM Workshop on CCD Backgrounds, Radiation Damage and Environments at Vilspa, Nov 29- Dec 1.

1.4 Update and improve CCD simulation

  ...  Continued re-calibration of S3 QE using sub-assembly and XRCF data and more accurate source/detector models in conjunction with CXC Cal group.

  ...] Finished testing tritium sources used in sub-assembly calibration for a soft electron component using both filters and magnets.  No particle background found at the level of the External Calibration Source however a smaller contribution cannot be discounted.

  ...  Continued effort to model the electron concentration in the CCD channel as a function of Fermi potential in the channel.  The CCD model and the flight software CTI corrector requires this relationship for accurate results.

  ...  Continued work on introducing FI CCD CTI effects in the CCD model.


2. Engineering

2.1 Instrument hardware engineering performance

 [...  Assisted CXC OCC personnel in investigating ACIS DPA anomaly of Oct. 26 and writing a failure report.


2.2 Instrument science performance

  ...  Continued daily quick-look processing of ACIS telemetry.

  ...  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 using new "cuckoo" clocking mode data.

  ...  Continued to support the Web interface to ACIS real-time data.

2.3 Participate in Chandra activities

 [...] Supported squeegee and the new cuckoo clocking mode tests including load and CAP review, and real-time command checking and data analysis.

3. CXC Support

3.1 Provide user support

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


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.


New ACIS Memo:

193 - Simple charge loss model

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

Outreach:

"Monitoring the Charge Transfer Inefficiency of ACIS and the Impact of the Varying Cosmic-Ray Background" presented by Catherine Grant (11/11/00, HEAD, Honolulu)