ACIS Instrument Support - Monthly Progress Report for July 2002

1. ACIS Characterization

1.1 Characterize and model radiation damage in ACIS CCDs

  ...  Continued analysis of no-squeegee cuckoo data.  Work continues on
defining a correction factor that improves performance.  Submitted 
manuscript to SPIE conference proceedings, will be presented in August.

  ...  Continued running charge injection tests on I0 from the command 
load.  Tests will determine the correspondence between voltage settings and 
amount of injected charge.  Two tests at an energy of around 600 eV, one 
test at an energy of around 3.6 keV.  Updated memo on charge injection 
analysis (ACIS memo #199J).

 [...  Began preparations for September irradiation/bakeout test at GSFC's 
particle irradiation facility.  Visted GSFC to discuss facility and 
interfaces.  Re-examined previous flight experience with bakeouts and 
radiation damage.  Prepared hardware and software.  Released memo "Goals 
and preliminary plan for a cold CCD irradiation experiment" 
(http://space.mit.edu/ACIS/rt_02.ps.gz).

1.2 Design and characterize alternative CCD readout modes

  ...  Supported charge injection tests on-board with lab verification and
testing.

1.3 Monitor scientific on-orbit performance of ACIS

 [...] Conducted sixth CTI measurement in alternating exposure mode with 
frame times of 4.0 and 3.2 seconds (ObsID 61114).  Recalibrated detrending 
factor used to remove influence of background on variability of measured 
CTI.  (http://space.mit.edu/~cgrant/cti/altexp.html).

  ...  Continued analysis of ExtCalSrc data to search for putative QE
decrease at low energies.  Updated with more recent data.  New data clearly 
shows a reduction in the rate of QE loss.  Well fit to an exponentially 
decreasing optical depth model.  Investigating apparent differences between 
external calibration source time dependence and gratings measurements.

  ...  Continued monitoring of ACIS CTI.  No significant changes beyond the
longterm slow increase.  Updated 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.
Updated web page (http://space.mit.edu/~cgrant/gain/).

1.4 Update and improve CCD simulation

  ...  Continued work on detailed physical model of FI CCD including CTI and
sacrificial charge.  Worked on a version of the simulator that can be
incorporated into MARX.

 [...] Modified BI CCD simulator to introduce flight-like time stamps into 
the output events.

 [...] Worked on the comparison of the flight spectrometer data and the BI 
CCD simulator results at low X-ray energies.

 [...  Worked on SPIE conference proceedings paper describing BI CCD 
simulator.  Will be presented/submitted in August.

2. Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.

2.2 Flight software maintainence

 [...  Reviewed proposed ACIS optical patches Rev C documentation.  
Software Review to be conducted in August.

2.3 Instrument science performance

  ...  Continued testing new CC mode bias parameters.  Second run is 
ExtCalSrc CC mode with new bias algorithm.  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.

  ...  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

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

2.4 Participate in Chandra activities


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 to maintain ACIS calibration database of ground and flight
data products

 [...] Advised CXC Cal personnel on CCD simulator parameter settings.

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:

199J - Charge Injection Test on ACIS (updated)

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


Outreach:

none