ACIS Instrument Support - Monthly Progress Report for July 2005

1.  ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Cold irradiation and bakeout test at GSFC, May 2005
      * Continued analyzing gsfc data including cti VS 
temperature from warmup set.  Began analysis of charge loss 
for events with precursors vs events without

  ...  Investigated time dependence of pulseheight sag in the central 
columns of FI CCDs (pulseheight sag first documented in ACIS memo #172
dated October 1999).  Increse in sag is roughly understood and is not
considered worrisome.  

  ...  Began a 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.  Reviewed proposed
parameter block for flight temperature scan.  Two observations 
done this month: ObsID 59530 at a setpoint of -100C and ObsID 59526 at 
a setpoint of -110C.

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

1.3 Monitor scientific on-orbit performance of ACIS

  ...  Submitted SPIE Proceedings paper on long-term trends in ACIS
radiation damage.  Will be presented at SPIE meeting in August and
published in Proc. SPIE 5898.

  ...  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)

1.4 Update and improve CCD simulation

  ...  Continued effort to improve fidelity of the BI CCD simulator
at low energies.  Did final verification of the new version.  Compiled
new version under solaris and linux.  Code transfered to CXC and
successfully tested.


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance. The 
ACIS instrument continues to operate nominally, with two exceptions:

     * The first "T-Plane latchup" in 44 months.  This known bug in the 
ACIS system causes the loss of science data on affected CCD channels, 
typically for a single science observation (as was the case this time).  
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.

     * Red limit warning riggered on one of the DEA power supply 
voltages during a test run with the CCD focal plane at -100C.  
The particular voltage limits had been set to alert us to off-nominal 
conditions, and -- having commanded an off-nominal condition -- we 
tripped the limit.  The hardware itself was functioning as it always 
had; we've written a note to file to remind us of this instrument property.

2.2 Flight software maintenance

  ...  Discussed ObsID 5645 telemetry corruption anomaly (SPR 138)
at monthly ACIS operations team meeting.

2.3 Instrument science performance

  ...  Participated in email discussion of possible ACIS bakeout.
Submitted summary of ground irradiation/bakeout experiments and
MIT ACIS team evaluation of the risks to the detector.  Sent most
recent Mn-L/K line ratio data to MSFC.

  ...  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
T-plane latchup of 9 July (see above), telemetry corruption anomaly
(SPR138, see June report), and PSMC thermal excursions.


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 SDS on implementation of serial CTI
correction.  Will be tested using MIT supplied calibration 
products for S3 at -120C.

  ...  Participated in CXC Cal/Ops modelling discussion group.
Discussed trapmap creation and verification proceedures.

  ...  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.  


Outreach:

None


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