ACIS Instrument Support - Monthly Progress Report for May 2003

1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continued running charge injection tests on S2 from the command 
load.  One test repeating an earlier run to increase statistics.

 [...  Preliminary analysis of charge injection tests shows a linear 
dependence of CTI measured from cal source lines and measured from 
charge injection.  Analysis ongoing.

  ...  New set of charge injection tests on I3 to begin in June.

 [...] Presented poster and oral presentation at the "IEEE workshop
on CCDs and advanced image sensors" describing the results of the 
cold irradiation/bakeout experiment performed last September. 
Submitted proceedings paper.

1.2 Monitor scientific on-orbit performance of ACIS

  ...  Continued analysis of ExtCalSrc data to search for efficiency 
decrease at low energies.  Improved analysis technique of Mn-L/Mn-K 
ratio on S3.  Doesn't change previous conclusions (higher contamination
than required by LETG analysis, declining rate of deposition).  
Provided pre-launch cal source data to Alexey Vikhlinin for comparison
purposes.

  ...  Continued monitoring of ACIS CTI.  No significant changes beyond 
the long term slow increase.  (http://space.mit.edu/~cgrant/cti/)

 [...] Searched for serial CTI trends on I3.  None found.

  ...  Continued monitoring of ACIS gain.  All CCDs stable with a slow 
decline in gain slope (ADU/eV) except for I2 which continues to vary.
(http://space.mit.edu/~cgrant/gain/).

1.4 Update and improve CCD simulation

  ...  Continued work on improving FI and BI CCD models with a more 
physical representation of the electron traps that cause CTI.


2. Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.  A 
review of the past 60 days of engineering data shows all systems operating
normally.

 [...] A test of the cold radiator demonstrated that we have two degrees of
control margin on our focal plane temperature with all CCDs clocking.  This
indicates essentially no degradation in performance since launch.

2.2 Instrument science performance

 [...] Reported to ACIS operations working group on the percentage of
CTI pad times with acceptable focal plane temperature under the current
pad time paradigm (acceptable temperature defined as <= -119.5C).
On average approximately 60% of pad times are entirely cold.

 [...  Reported preliminary results to the ACIS operations working
group on the dependence of CTI, gain and line width to small
(few degrees) changes in the focal plane temperature.  Results
may indicate that calibration changes due to temperature are
larger than previously thought.  Analysis ongoing.

 [...] New CC mode bias parameters tested on board including higher
split threshold.  Analysis forthcoming.

  ...  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 ACIS telecon.

  ...  Continued to support charge injection operations by reviewing 
loads and comparing flight data to ground data to select new settings.


3. CXC Support

3.1 Provide user support

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

 [...] Provided support for potentially hazardous Sco X-1 observation
including quick look analysis tools and real-time support.  Observation
canceled due to radiation shutdown.

 [...] Participated in discussion with cal team on the absolute QE
of the ACIS CCDs.

 [...] Discussed sacrificial charge algorithm developed last year
with CXC.

3.2 Provide data analysis support

 [...] Participated in CXC Cal/Ops RMF 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.


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