ACIS Instrument Support - Monthly Progress Report for October 2000


1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continued analysis of calibration data of radiation damaged CCD, w457c1.

  ...  Continued 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.

       * 01-02 October - Ran 16-row squeegee with no initial flush frames on I0 before and after perigee passage to test hypothesis that initial charge excess depends on startup conditions.  Initial charge the same for both tests. (L14-L15, ObsID 61898, 61896)

 [...  Began 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. 

       * 04 October - (L16, ObsID 61892)
       * 07 October - (L17, ObsID 61890)
       * 10 October - (L18, ObsID 61888)
       * 12 October - (L19, ObsID 61886)
       * 15 October - (L20, ObsID 61881)
       * 18 October - (L21, ObsID 61878)
       * 20 October - (L22, ObsID 61876)
       * 28 October - (L23, ObsID 61867)

  ...  Continued characterization of column to column variation of radiation-damaged lab CCD, w459c1.  (ACIS Memo #192)

1.2 Define and characterize alternative CCD readout modes

 [...  Designed and 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.  Will test in real-time on a flight device in November.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued monitoring of ACIS CTI.

1.4 Update and improve CCD simulation

 [...] The model of the backside CCD response was modified and the executable was made available to CXC and SAO. It now runs on their computers.

 [...] HIREFS data for backside flight devices taken during the subassembly calibration were reanalyzed and made available to CXC.

  ...  Continued re-calibration of S3 QE using sub-assembly and XRCF data and more accurate source/detector models.  New BI RMF (provided by Norbert Schulz) yields slightly better fits but little change in results.

 [...  Began testing tritium sources used in sub-assembly calibration for a soft electron component, similar to that found for the External Calibration Source.  

  ...  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

 [...  An anomaly of the DPA side A occurred on Oct 26.  While out of contact the DPA transitioned within a major frame from performing nominally to off (zero current and voltages).  No overcurrent was detected.  Within the same comm pass as the problem discovery, the DPA was powered on and science operations resumed.  Investigation ongoing.

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.

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

2.3 Participate in Chandra activities

 [...] Supported real-time activities during DPA anomaly on October 26 including command checking and real-time 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:

192 - Column to column variations in squeegee mode

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