ACIS Instrument Support - Monthly Progress Report for May 2013

1.  ACIS Characterization

1.3 Monitor scientific on-orbit performance of ACIS

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

  ...  Proposed conducting a series of ECS measurements at elevated temperatures as was done in 1999 and 2005 (Grant et al. 2006, SPIE 6276).  Shape of dCTI/dT reflects the blend of trap time constants.  In the likely event that ACIS nominal focal plane temperature will need to be increased at some point, having better performance statistics at potential new temperature set points seems prudent.  Initial plan is to take data at -115C and -110C, then decide how much more data is required and at what other temperatures.

  ...  Continued work on a paper combining CTI, FWHM and background monitoring results from ACIS and Suzaku.  Final edits on paper continuing.

  ...  Collected new raw frames and updated monitoring web page.  (http://space.mit.edu/~fergason/acis/raw.html)


2.  Engineering

2.1 Instrument hardware engineering performance

  ...  Continue to monitor long term ACIS instrument performance.  ACIS continues to perform nominally with one exception...

  ...  During ObsID 15232 on May 16, ACIS stopped sending exposure or event packets from two of four FEPs that were processing the four active CCDs.  The other pair of FEPs continued normally.  This behavior closely paralleled that in two prior observations, and the instrument team concludes that the most likely explanation is that an electrical transient caused the two FEPs to reset.  Full report is here (ftp://acis.mit.edu/pub/acis-obsid-15232-anom.pdf).

2.2 Flight software maintenance

  ...  Engineering Unit currently running on a reasonably modern Solaris workstation.  Testing continues on a Linux CentOS 5 workstation as an eventual replacement.  Requires changing hardware interfaces which is still under test.
 
2.3 Instrument science performance

  ... Participated in monthly ACIS operations meetings.  Discussed the May 22 radiation shutdown, the ObsID 15232 anomaly, the status of the Linux porting, and plans for future warm ECS measurements.

  ...  First ACIS-triggered radiation shutdown occurred on May 22.  ACIS detected elevated and increasing threshold crossing rates, and set the appropriate bilevels which caused the Chandra OBC to run SCS 107.  HRC was about 2/3 of the way to its limit when ACIS triggered.  The radiation event was hard and with a fast rise time, which is ideal for detection by the ACIS algorithm.  Four FI CCDs were running, so signal from the average threshold crossings data was not noisy.

  ...  At the request of CDO, re-examining the TXINGs triggering algorithm.  Currently requires increasing rates, but are we missing valid radiation events by ignoring high but decreasing rates?  Testing a wider range of TXINGs parameters including allowing for decreasing rates.  Completed a better indexing of existing radiation shutdown characteristics.

  ...  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.


3.  CXC Support

3.1 Provide user support

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

  ...  Answered user questions on using ECS data to doublecheck accuracy of gain calibration.

3.2 Provide data analysis support

  ...  Participated in CXC Cal/Ops ACIS response discussion group.  Discussed contamination analysis and CC mode calibration.

  ... Submitted summary of CCD working group activities and edited IACHEC newsletter.  Published on astro-ph (http://arxiv.org/abs/1305.4480).

  ...  Answered SDS questions on "noise" in gain measurements and exposure time in the frame-transfer streak.

  ...  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.  Plan for broken EGSE backup machine is to do nothing for now, but proceed with upgrades to Linux.

  ...  Migration of MIT realtime telemetry software to Linux continues.  A report on the port of MIT software to CXC linux is here (ftp://acis.mit.edu/pub/acis-linux-port-v1.0.pdf)


Outreach:

* Gave a presentation about Chandra to elementary school students (LaMarr)