ACIS Instrument Support - Monthly Progress Report for December 2000


1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Update of 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 collection of raw data in "cuckoo" clocking mode which allows for more efficient data telemetry.  More cuckoo observations planned for January and February on all I-array CCDs.

       * L29-L40 (many ObsIDs) 10 successful runs of 16-row squeegee in cuckoo clocking mode on I3 (focal plane temperature too warm for one run)

 [...  Began analysis of cuckoo squeegee data.  Long time constants of electron traps determined by analyzing the shape of the tail behind the squeegee row.  Model used was significantly improved.  Short time constants measured by analyzing the signal behind Mn-K alpha X-ray events.  Relative trap densities also determined.

  ...  Complementary analysis of cuckoo data and possible flight correction algorithms proceeding in parallel.

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.  No significant changes detected.

 [...  Began study of background flares using S3 amplitude reject rate.  Little to no correlation of flare occurence with altitude.  Distinct periods of quiescence and strong flaring observed.  Memo forthcoming.

 [...] Checked for a substantial increase in hot pixels (as seen on XMM).  A few new hot pixels detected, compared to dozens on XMM. 

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.

  ...  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

  ...  Continued to monitor hardware operations

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.

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