ACIS Instrument Support - Monthly Progress Report for June 2004

1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continuing test of our CTI/background relation by running
a series of alternating exposure mode observations with a grid
of exposure times.  In June there were three runs with a frametime
of 4.0s, 3.5s and 3.5s (only the first had a cold focal plane 
temperature), alternating with a standard frametime of 3.2s.
Additional runs in July should complete the set.

1.2 Monitor scientific on-orbit performance of ACIS

  ...  Continued monitoring of ACIS CTI.  Updated CTI monitoring web
page (http://space.mit.edu/~cgrant/cti/).

  ...  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/).

1.3 Update and improve CCD simulation

  ...  Continued work on improving FI and BI CCD models and CTI simulation 
code.

 [...] Presentation at SPIE meeting describing the MIT CTI correction
algorithm that is implemented as part of the CXC pipeline.

 [...] Presentation at SPIE meeting describing results of a very accurate 
measurement of charge loss as a function of signal charge in a pixel.  This 
dependence is important for the correct modeling of the CTI.

2. Engineering

2.1 Instrument hardware engineering performance

 [...  Participated in a meeting to work out detailed procedures and 
contingency plans for the actual execution of an ACIS bakeout.

  ...  Continue to monitor long term ACIS instrument performance.
ACIS engineering data continues to be stable.

2.2 Flight software maintenance

 [...  A probable ACIS anomaly was discovered during ObsID 5008 on
June 22.  An uncommanded reset of all the FEPs terminated this 
observation after only 18.6 ksec of a scheduled 26.9 ksec.  The FEP
reset normally for the next observation.  An ACIS Software Problem
Report was opened and the available data is being analyzed.
(http://acis.mit.edu/axaf/spr/prob0136.html)

 [...] ACIS flight software patch (Rev C of Flight Software Optional
Patches) was successfully loaded on June 3.

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 ACIS telecons on the possible ACIS bakeout.

 [...] Characterize the performance change from a bakeout by comparing
CTI and FWHM in each node on S3.  The node-to-node CTI variations
can be used to represent the bakeout induced CTI change.  Included as
part of the ACIS bakeout risk estimate.

 [...] Supported ACIS bakeout community-wide briefing on June 8.  
Contributed data and slides for the presentation materials.  Participated
in person and on the telephone.  Mark Bautz presented the ACIS team's
ground and flight experience with bakeout, a model for the CCD reverse
annealing, and predictions from the model for a future bakeout.

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

 [...] Participated in CXC Cal/Ops RMF discussion group.  Continued
discussions on improvements in QE and QEU.

  ...  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.


Outreach:

Two relevant presentations at the SPIE Astronomical Telescopes and
Instrumentation meeting in Glasgow, Scotland, June 21-25.  Will be
published in Proc. SPIE vol. 5501

- Prigozhin, "X-ray CCD with charge injection structure"
- Grant, "A charge transfer inefficiency correction model for the Chandra 
Advanced CCD Imaging Spectrometer"


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