ACIS Instrument Support - Monthly Progress Report for April 2002

1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continued collection of raw data in "cuckoo" clocking mode which allows for more efficient telemetry of raw data. 

       * CL43-44, 1 successful run of no-squeegee cuckoo clocking on I3 Node 3 (focal plane temperature too warm for one run)

 [...] Sacrificial charge analysis of no-squeegee cuckoo data used to esimate parameters for the longest time constant trap (ACIS memo #198)

  ...  Continued analysis of no-squeegee cuckoo data.  Work continues on defining filters and correction factors that would improve over-all performance.  Presented preliminary results at April HEAD meeting (http://space.mit.edu/~cgrant/HEAD02.poster.ps.gz) and wrote ACIS memo #200.

 [...  Successfully ran charge injection test on S0 in the load.  Data were taken without any compression to circumvent problem seen in March real-time test.

1.2 Design and characterize alternative CCD readout modes

  ...  Supported charge injection tests on-board with lab verification of commands.  Tested charge injection on a back illuminated CCD with no ill effects.  Screened multiple flight-like CCDs with similar results.
 
1.3 Monitor scientific on-orbit performance of ACIS

  ...  Continued Analysis of ExtCalSrc data to search for putative QE decrease at low energies.  Added data taken at -110C.  Both pre-flight measurements (taken at Ball and at TRW) are consistent with each other and with the first of the OAC measurements.  

  ...  Testing calibration sources in the lab to determine is any of the change in the Mn+Fe-L/Mn-K ratio measured onboard could be due to intrinsic changes in the source.  No change seen over many years for lab 55Fe sources.  Retrieving flight spare source for future testing.

 [...] Confirmed that measured decay rate of Mn-K line is consistent with expected radioactive decay of 55Fe.  

  ...  Continued monitoring of ACIS CTI.  No significant changes detected.

 [...] Participated in Chandra quarterly review

1.4 Update and improve CCD simulation

  ...  Continued work on detailed physical model of FI CCD including CTI and sacrificial charge.

  ...  Reanalyzing HIREFS calibration data of S3 to compare to CCD simulator output and to better understand gain function at very low energies.  Attempting to quantify the influence of flux on measured gain.


2. Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.  Everything looks nominal.

2.2 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.

  ...  Continued to develop flight s/w algorithms to implement "Squeegee" clocking mode and to report precursor charge from ACIS CCDs.

  ...  Participated in ACIS telecons

  ...  Participated in ACIS operations meeting

2.3 Participate in Chandra activities

 [...] Supported charge injection test on S0 run on 10 April 2002.  Including load review and post-test analysis


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.

 [...] Supported preparation for ACIS calibration session at April HEAD meeting

  ...  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.


New ACIS Memo:

198 - Estimating the long time constant
199 - Charge Injection Test on ACIS
200 - Preliminary Sacrificial Charge Correction

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


Outreach:

Presentations at April HEAD meeting:
"Chandra Observations of a Proto-cluster at z=3.1" by Mark Bautz
"Sacrificial Charge and the Spectral Resolution Performance of ACIS CCDs" by Catherine Grant