ACIS Instrument Support - Monthly Progress Report for April 2005

1.  ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Planning for next set of cold irradiation and bakeout lab
tests scheduled for May 9-20.  Assembled equipment for local 
verification before shipping to GSFC.  Tested data acquisition.

  ...  Finished fine tuning calibration products for S3 BI CCD
CTI correction (-120C only).  Products have been handed over to 
Glenn Allen, CXC SDS, to test implementation in acis_process_events.

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

1.3 Monitor scientific on-orbit performance of ACIS

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

  ...  Improved contamination monitoring.  Previously analyzed individual
observations for best time-resolution.  Decreasing low energy counts due
to radioactive decay and contamination has made this increasing unreliable.
Now adaptively bins multiple observations for better signal to noise.

  ...  Began preparing materials for the ACIS SI team report for the
upcoming Chandra Quarterly Review in May.

1.4 Update and improve CCD simulation

  ...  Continued effort to improve fidelity of the BI CCD simulator
at low energies.  LETG data at energies above and below the silicon
edge were analyzed and the parameters of the simulator were tweaked
to reduce the discrepancy between the data and the simulation.  Previous
analysis at energies below 1200 eV had to be redone in order to find
parameters that work throughout the entire energy range of the
available data from 494 eV to 1984 eV.


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.  The 
ACIS instrument continues to perform nominally with all engineering 
parameters stable. 

2.2 Flight software maintenance

  ...  Identified anomaly in the processing of data packets by the back 
end processor which results in the loss of one or two science data packets.  
By reviewing all of the previous science data collected since launch, we 
see that this anomaly (presumably a software bug) has been with us since 
the start of the mission.  It manifests itself as a contention between 
housekeeping and science packets in a very small time window; we are 
observing about 2 such anomalies per year.  Investigations assisted by 
our laboratory test bench are continuing.

2.3 Instrument science performance

  ...  Participated in ACIS telecon on possible ACIS bakeout.  Discussed
plans for GSFC irradiation experiments.

  ...  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 operations meeting.  Discussed plans for
GSFC irradiation experiments, focal plane cooling tests, and the new
anomaly discovered in ObsID 5645.


3.  CXC Support

3.1 Provide user support

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

3.2 Provide data analysis support

  ...  Working with CXC Cal on CTI correction calibration.  Debugged
problem with S0 map and retested.  Problem seems to be fixed and
results are better than before.

  ...  Participated in CXC Cal/Ops modeling discussion group. Discussed
CTI correction for S3 and improvements in the BI CCD model.

  ...  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.  

  ...  ACIS EGSE move is essentially complete.  Old machines continue
to run in parallel for the time being.  Some issues with Squirt are
being evaluated.


Outreach:

None


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