ACIS Instrument Support - Monthly Progress Report for October 2005

1.  ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Completed 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/).  More analysis
will be included in a presentation at the May 2006 SPIE meeting.

  ...  Poster presentation at Six Years of Science with Chandra meeting
on the May 2005 radiation damage/annealing experiments.

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.  This was determined
to be a result of a side effect of the anomalous DEA shutdown on 
September 15.  All temperature readings between September 15 and October
16 were ~ 1.3 degrees warmer than the actual temperature.  After
correcting the temperature readings, no CTI anomaly remains.

  ...  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)

  ...  Investigated a gain anomaly in the I0 and I2 CCDs in which the
detector gain increased by ~1% at 6 keV during the late summer.  This
is believed to be the same effect as has been seen on I2 since early on,
but larger.  

  ...  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.

  ...  Presentation at Chandra Calibration Workshop on ACIS performance
monitoring.

  ...  Presented ACIS SI team report at the Chandra Quarterly Review.

1.4 Update and improve CCD simulation

  ...  Presentation at Chandra Calibration Workshop describing the improved
low energy response in the BI CCD model.


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  The anomalous DEA shutdown on day 258 (previously reported) had one 
further side effect of which we were initially unaware.  Because of the 
way in which we recovered from that event -- sending no commands which 
were not necessary for the DEA recovery -- we did not follow the 
procedure for a /general/ power outage.  That procedure would have 
reloaded the software in the DPA by means of a soft reset, but it is 
precisely that reset which calibrates the housekeeping A/D converter in 
the DEA (which must happen at least a few seconds after the DEA is 
initially powered up).  The net result was that for a period of about 
two weeks the housekeeping values reported by ACIS were of reduced 
accuracy -- including an apparent increase in the focal plane 
temperature of 1.3 degrees C.  Having finally realized our error, we 
issued a soft boot command and are now again operating with perfect 
normalcy.

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

2.3 Instrument science performance

  ...  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.

  ...  Participated in "monthly" ACIS operations meeting.  Discussed
DEA anomaly and related housekeeping anomaly.

2.5 Participate in Chandra activities

  ...  Suported real-time commanding of ACIS soft boot to calibrate
the housekeeping A/D converter.


3.  CXC Support

3.1 Provide user support

  ...  Presentation at Chandra Calibration Workshop on 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.

  ...  Supported CXC Cal effort to quantify errors in calibration.
Provided guidance on CCD QE model and model parameters.  Data used
in Chandra Calibration Workshop presentation.

  ...  Continued to maintain ACIS calibration database of ground and 
flight data products.  Replaced failed disk containing ACIS ground
calibration data.


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:

Talks at Chandra Calibration Workshop, 31 Oct 2005
     * Grant, "ACIS instrument status and performance evolution"
     * Prigozhin, "Improved model of BI CCD response at low energies"

Poster at Six Years of Chandra Science meeting, 2-4 Nov 2005
     * LaMarr et al., "Recent ACIS CCD Irradiation Experiments"

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