ACIS Instrument Support - Monthly Progress Report for March 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)

  ...  Compared history of ACIS overclock levels to electronics
  temperatures.  Found they are well correlated.  Are using this
  correlation to determine new video offset values to prevent any
  nodes from dropping below 0 ADU.

  ...  Updated web page examining bias data before and after Crab
  observations to include most recent one (ObsID 13206 on Mar 15).  No
  changes observed.

  ...  Continued work on a paper combining CTI, FWHM and background
  monitoring results from ACIS and Suzaku. Further data analysis
  improvements.  Submitted related abstract for May AAS 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.


  ...  ACIS anomaly occurred on March 8 when, after a normal bias, the
  I0 CCD (connected to FEP5) failed to report any events for an entire
  science run.  No relevant errors were found in the telemetry and no
  obvious cause was immediately apparent.  The ACIS team decided to
  plan a real-time CAP to observe the next use of the I0 CCD and to
  either stop the command load or run diagnostic procedures, depending
  on the state of the instrument.  The next use of the I0 CCD
  proceeded nominally and it was decided that it was unnecessary to
  interrupt the command load.  The cause has not been uniquely
  determined but a leading candidate is a comic-ray upset.

2.2 Flight software maintenance

  ... Reviewed CAP in response to the March 8 ACIS anomaly to examine
  data from I0 during ObsID 55605 (in the command load) and possibly
  intervene and start two ECS measurements with all 10 video boards
  powered on.

2.3 Instrument science performance

  ...  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.
  Provisionally approved at ECO review, however further revisions are
  underway to reduce the false positive rate and will require another
  review.

  ...  Examined threshold crossings data around recent solar activity
  (Mar 10) to see if ACIS patch would have triggered.  Rates did not
  reach high enough levels to trigger a shutdown.

  ...  Participated in monthly ACIS operations meeting.  

  ...  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

  ...  Answered user questions on inconsistent measured values of
  cluster kT for the same object in different observations.  Pointed
  out that the focal plane temperature was more than a degree
  different between the observations and that the direction of the kT
  change was consistent with the effects of changing CTI.  Suggested
  reanalyzing with CIAO 4.3, which includes temperature-dependent CTI
  correction.

  ...  Updated ACIS memo listing calibration ObsIDs and observation
  characteristics (ACIS Memo #165).

3.2 Provide data analysis support

  ...  Planning for upcoming IACHEC meeting (International
  Astronomical Consortium for High Energy Calibration).  Chairing
  working group on CCD issues which will discuss calibration of timing
  modes.

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

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

  ...  Finished transfering all ACIS monitoring analysis scripts and
  data to a new computer and new OS (from Solaris to Mac).

4.  OCC Support

4.1 Use of MIT/ACIS EGSE at OCC

  ...  Provided real-time support during March 8 ACIS anomaly.

  ...  Continued support and maintenance of ACIS EGSE software and
  hardware at the OCC.



Outreach:

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