ACIS Instrument Support - Monthly Progress Report for May 2006

1.  ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Submitted SPIE proceedings paper on temperature dependence of
ACIS CTI.  Paper compares 1999 data to 2005 data from -120C to -60C.
Presented paper at SPIE meeting.

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Responded to an issue reported by CXC MTA in which bias values 
for two CCD nodes suffered an anomalous jump.  The anomaly was not 
seen in ACIS team data and appears to be the result of a software 
error at CXC.

  ...  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)

  ...  Continued work on memo for the operations team on the 
consequences of a future, unprotected radiation belt transit by ACIS.  
Awaiting final inputs, then will circulate to wider distribution.


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance. The 
instrument continues to perform nominally.  A review of the last two 
months engineering data indicates no untoward behavior, by either the 
instrument or its keepers.

2.2 Flight software maintenance

  ...  ACIS BEP went into trickle bias mode on day 129 (May 9).  This
can trigger a threshold-plane latchup in the FEPs with loss of science
data in one or more CCDs, but in this case did not.  This is the 
seventh instance of this anomaly on-orbit and the third instance 
without a FEP latch-up.  As long as the event remains infrequent, the 
ACIS team has consistently recommended against uploading a (developed 
and tested) patch to resolve the problem, simply in the unlikely event 
that the fix might introduce other undesirable behaviors.  The 
original report on this type of anomaly can be found here: 
http://acis.mit.edu/asc/tplaneanom1.html

2.3 Instrument science performance

  ...  Supported review of ACIS thermal limits and proposal to increase
three DEA/DPA temperature yellow limits.

  ...  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).

  ...  Answered colleague's questions about calibration source data in
the CXC archive.

3.2 Provide data analysis support

  ...  Participated in CXC Cal/Ops modelling discussion group.  
Discussed (among other things) the apparent QE "edge" feature near the 
Si-K edge and incorporating the August 2005 gain jump on I0 and I2 
into the time dependent gain correction.

  ...  Discussions with colleague of apparent QE "edge" feature near
Si-K edge.  Provided data on fluorescence and escape peaks in ACIS 
CCDs.  A rough empirical model of the escape peak around the event
threshold provides a reasonable fit to the apparent QE "edge".

 ...  Answered project science question about current detection 
efficiency.

  ...  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:

Poster presentation at SPIE conference 6276, "High Energy, Optical, 
and Infrared Detectors for Astronomy II", 25-27 May 2006
     * Grant, et al., "Temperature dependence of charge transfer 
       inefficiency in Chandra X-ray CCDs" (astro-ph/0606178)


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