ACIS Instrument Support - Monthly Progress Report for June 2007

1.  ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Reported on the temperature dependence of CCD performance
to ACIS calibration group.  CTI, pulseheight and FWHM are all
temperature dependent to some extent on both FI and BI CCDs.
A few percent of ACIS science observations suffer from warmer
temperatures that adversely effect performance.  This percentage
may be increasing.

  ...  Developed and tested a preliminary temperature-dependent
CTI correction algorithm.  Successfully removes temperature-dependence
of pulseheight, slightly decreases temperature-dependence of FWHM.
Presented results to ACIS calibration group.  Continuing investigation.

  ...  Continued work on a paper presenting the results of
the radiation damage/reverse annealing tests done at GSFC in 2005.

  ...  Executed new SI modes which allow more grades to be 
telmetered.  These SI modes will be used to compare TE and CC mode 
grade rejection to help calibrate CC mode.  Five ObsIDs (58367, 58364,
58358, 58349, 58340) so far.  Differences in flight grade distribution
between TE and CC mode are roughly consistent with our understanding
of ACIS trap properties.  Continuing to investigate performance
differences.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued investigation of bias artifacts believed to be
due to long-lived cosmic ray afterglows  Worked with CXC SDS/DS
to allow for data processing using superbiases.

  ...  Continued monitoring of ACIS CTI, gain, trailing pixel 
pulseheight, detector efficiency, corner pixel distribution, and 
spectral line centroid and width.  Updated monitoring web pages.
(http://space.mit.edu/~cgrant/monitor.html)

  ...  Collected new raw data frames.  Plan regular collection of
raw frames to help with diagnosing future problems and better 
understanding of cosmic ray artifacts.

1.7 Produce novel data products from the MIT ACIS database

  ...  Summed raw data frames to simulate longer frame times, such
as those originally proposed for ACIS (in the 80s).  Fraction of
imaging area lost to cosmic rays becomes very large.


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.
ACIS continues to function normally.  A review of the engineering 
telemetry for the past 60 days reveals no change in the nominal 
instrument status.

2.2 Flight software maintenance

  ... Continued documentation and testing of the next ACIS patch
release, which will include the "tlmbusy" and "buscrash" patches.
These patches address the issues reported in Software Problem
Reports 138 and 140 (http://acis.mit.edu/axaf/spr/prob0138.html
and http://acis.mit.edu/axaf/spr/prob0140.html)

2.3 Instrument science performance

  ...  Participated in monthly ACIS operations meeting.  Discussed
new flight software patch, thermal issues and new TE/CC mode
diagnostic tests.

  ...  Continued daily quick-look processing of ACIS telemetry 
and maintained Web interface to ACIS real-time data.

  ...  Continued to publish the "annotated DOT" timeline reports.


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

  ...  Participated in CXC Cal/Ops modeling discussion group.
Discussed CC mode calibration, temperature-dependent performance
and temperature-dependent CTI correction algorithm.  Investigated
possibility of CC3x3 mode event histograms; not possible without
patching flight software.

  ...  Continued to maintain ACIS calibration database of ground 
and flight data products.


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.

  ...  Continued work on improving configuration management of 
the ACIS workstations in the TST area of the Chandra OCC.  Work 
nearly complete.


Outreach:
Bautz:  Talk on the history of ACIS at "40 Years of X-ray Astronomy" 
workshop in honor of Gordon Garmire.

None

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