ACIS Instrument Support - Monthly Progress Report for January 2001


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).

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

       * L41-L45 (many ObsIDs) 4 successful runs of 16-row squeegee in cuckoo clocking mode on I3 (focal plane temperature too warm for one run)

       * L46-L47 (ObsIDs 61773, 61768) 2 successful runs of 16-row squeegee in cuckoo clocking mode on I0

       * L48-L50 (ObsIDs 61763, 61758, 61754) 3 successful runs of 16-row squeegee in cuckoo clocking mode on I1

  ...  Continued analysis of cuckoo squeegee data.  Long time constants of electron traps determined by analyzing the shape of the tail behind the squeegee row.  Short time constants measured by analyzing the signal behind Mn-K alpha X-ray events.  Relative trap densities also determined.  Investigated column-to-column variations of the trailing distributions.

  ...  Complementary analysis of cuckoo data and testing of flight s/w algorithms from FI CCDs due to charge traps.

 [...  Analyzed lab data from radiation damaged CCD, w459c1 using trailing charge from X-rays to help determine charge/volume relation.

1.2 Define and characterize alternative CCD readout modes

  ...  Prepared, verified and tested new "cuckoo" clocking mode with 8-row squeegee on the engineering unit.  Real-time flight test planned for 16 Feb.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued monitoring of ACIS CTI.  Updated CTI web page (http://space.mit.edu/~cgrant/cti/cti120.html). No significant changes detected.

 [...] New ACIS Memo #194 studying background flares using S3 amplitude reject rate.  Little to no correlation of flare occurence with altitude.  Distinct periods of quiescence and strong flaring observed.

 [...  Began monitoring of ACIS gain stability.  Memo forthcoming.

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).

3.2 Provide data analysis support

 [...] Consulted with CXCDS on issues relating to ACIS timing and continuous-clocking bias anomalies.

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 Memos:

193 - Simple charge loss model (revised)
194 - ACIS background flares and Chandra orbital position

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