ACIS Instrument Support - Monthly Progress Report for September 2005

1.  ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continued test to measure CTI at different focal plane temperatures.
These results will be used to both understand the discrepancies between
the 2002 and 2005 ground radiation tests, which may be at least partially
due to different baseline temperatures, and to update our knowledge of 
CTI temperature dependence from 1999 to the present.  Preliminary analysis
posted to the web (http://space.mit.edu/~cgrant/ctitemp/).  Final
observation at -95C rescheduled for October.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Investigating a CTI anomaly in the FI CCDs in which the measured
CTI decreased by 4e-6 between September 12 and 17.  Investigation is
ongoing.

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

  ...  Updated CTI monitoring to include a grade filter for S3 which
removes all but single pixel (G0) events.  This lowers the background
levels substantially and allows for better fitting.

  ...  Continued work on memo for the operations team on the consequences
of a future, unprotected radiation belt transit by ACIS.  Motivated
by recent Chandra safe mode simulation. 

  ...  Continued taking a series of data in full-frame raw mode for
performance verification and monitoring.  Two ObsIDs this month with
data in both the ACIS-I and ACIS-S configurations.

1.4 Update and improve CCD simulation

  ...  New version of BI CCD simulator released to CXC.  This version
fixes a bug which cause an anomaly in the shape of the response  function.


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  ACIS suffered an autonomous power shutdown of its DEA electronics, 
the third such autonomous shutdown in six years (the two previous shutdowns 
affected the DPA).  The symptoms lead to suspicions about a) spurious 
commands from the RCTU; b) a spacecraft charging event; or c) and SEU 
event.  Both of the later cases would have occurred in the PSMC.  As we 
found in the previous failure analysis, however, each of these causes is 
extremely unlikely, and there is no other evidence that would lead to 
establishing one of these as the cause.  We remain uncertain as to the 
root cause. 

  ...  Continue to monitor long term ACIS instrument performance. Besides
the anomalous DEA shutdown, the ACIS instrument continues to operate 
nominally.

2.3 Instrument science performance

  ...  Finished study of the ObsID 5645 anomaly (SPR 138, M05040701).
Prepared final version of report (ftp://acis.mit.edu/pub/SPR138-1.0.pdf)
which will be presented to the FDB for closeout in October.

  ...  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.

2.5 Participate in Chandra activities

  ...  Supported DEA restart after anomalous DEA shutdown including
analysis of housekeeping data, CAP review and real-time monitoring.


3.  CXC Support

3.1 Provide user support

  ...  Submitted abstract to Chandra Calibration Workshop to
discuss instrument status and performance evolution.

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

3.2 Provide data analysis support

  ...  Participated in CXC Cal/Ops modelling discussion group.
Discussed bug-fix of BI CCD simulator and the preliminary results
of the warm temperature CTI tests.

  ...  Supported CXC Cal effort to quantify errors in calibration.
Provided guidance on CCD QE model and model parameters.

  ...  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.  


Outreach:
none

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