ACIS Instrument Support - Monthly Progress Report for April 2011

1.  ACIS Characterization

1.3 Monitor scientific on-orbit performance of ACIS

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

  ...  Updated web page examining bias data before and after Crab
  observations to include most recent ones (ObsIDs 13207,
  13150-13154).  No  changes observed.

  ...  Continued work on a paper combining CTI, FWHM and background
  monitoring results from ACIS and Suzaku. Presented some preliminary
  results at IACHEC meeting.


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.  All
  ACIS engineering parameters continue to operate within predicted
  limits.

  ...  In anticipation of continued spacecraft heating, the ACIS team
  agreed to increase yellow limits on some temperatures.  Red limits
  are unchanged.

  ...  The ACIS Engineering Unit has developed an intermittent
  anomaly.  The cause is under investigation, but may be due to a
  noisy connection within the ACIS-I2 pixel input line to the DPA or
  DPA backplane.  A fix is being worked on.

2.2 Flight software maintenance

2.3 Instrument science performance

  ...  Constructed and reviewed parameter blocks to test potential new
  values for the CCD video offsets.  The new values prevent
  bias-uncorrected pulseheights from going below zero at higher
  detector temperatures which could potentially be reached in the
  future.  Flight testing is delayed due to problems with the ACIS
  engineering unit.

  ...  Continued investigation into whether ACIS can act as it's own
  radiation monitor, prompted by action from the thermal working group
  which is concerned about the continued degradation of EPHIN.
  Improvements to the algorithm have removed most of the false
  positives without any loss of sensitivity to real radiation
  conditions.  New version will need to be rereviewed.  

  ...  Participated in monthly ACIS operations meetings.  

  ...  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

  ...  Answered CXC SDS questions on the scientific underpining of the
  sub-pixel positioning algorithm.

  ...  Attended IACHEC meeting (International
  Astronomical Consortium for High Energy Calibration).  Chaired
  working group on CCD issues which discussed calibration of timing
  modes, and cross-mission comparisons of CTI measurements.

  ...  Participated in CXC Cal/Ops modeling discussion group. 

  ...  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.



Outreach:

Supported MKI participation in MIT Open House including giving talks
on X-ray astronomy, creating movies and manning exhibits on Chandra
and ACIS, and giving tours.