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Second Meeting of the IACHEC Contamination WG
10th IACHEC Meeting, Fragrant Hill Hotel, Beijing, China
20 April 2015 14:00-16:00 

Attendees

  • Doug, Eric, Wei, Vadim, Paul, Kallol, Herman

Agenda

Notes

  • Kallol described briefly the ASTROSAT LET (?) contam mitigation
    • one month before LET door opens
    • epoxy of one instrument is big concern, so might wait longer
  • Herman provided just the depth of C,O edge, not total tau at the edge
    • will give Eric total tau, but it will be modeled, not measured
  • Doug
    • accelerated accumulation since 2012 can only be explained by a source that is increasing
    • uses CALDB values since that's the best compromise between clusters and grating contamination measurements
    • first source is going down exponentially to a constant rate, second is going up exponentially
      • uses empirical temperature of the OBA (Optical Bench Assembly) which is level at first and then seems to go up exponentially
        • Herman wonders why it doesn't go up linearly, since presumably it's being heated because thermal blanket is being destroyed by particulates
        • maybe it was flat until heaters were turned off, and it went up and is now approaching a linear dependence
    • based on model of OBA temp going up exponentially, source rate goes up 30x in next 5 years
      • also volatility is very well constrained, under same temp change assumption, because of spatial dependence on OBF and ACIS-S vs. ACIS-I
      • higher volatility than initial stuff that built up
    • Herman mentioned Rosetta which tracked contamination
      • paper from several years ago, will try to track it down
      • used mass spectrometer to measure the atmosphere around the spacecraft en route
  • Herman
    • early and late contanimant are oxygen-rich, midtimes is oxygen poor
    • fluorine has been pretty constant
  • Eric
    • compare Henke and Verner cross-sections
  • white paper
    • ran out of time for discussion
    • Eric will prepare a skeleton paper, with sections for Suzaku/XIS filled in as example
    • Eric and Herman will talk about this at MIT over the summer
    • focus on current missions: tracking, monitoring, calibration

Action Items

  • A/I 1 DUE: March 30: Eric will ask Astro-H folks about any updates
  •  A/I 2 DUE: March 30: Eric will ask ASTROSAT folks to join (Kallol Mukerjee)
  • A/I 3 DUE: March 30: Eric will update the multi-mission plot with the information he has on ACIS,XIS,MOS and send it to Steve S. for display at EPIC cal meeting 
  • A/I 4 DUE: April 13: Herman, Steve S., Eric will send Eric tau_c, tau_o for instruments vs. time (XIS,ACIS,MOS) and space (XIS,ACIS) 
  • A/I 5 DUE: 2015 August 30: Steve S. will look up possible environmental effects to explain MOS1/2 differences 
  • A/I 6 DUE: 2015 August 30: Steve S. will ask about RGS contamination update, include slide
  • A/I 7 DUE: 2015 August 30: Eric: make differential rate plot, showing rate of build-up for Suzaku
  • A/I 8 DUE: 2015 August 30: Eric: combine RXJ1856 data and see if H has changed for Suzaku 
  • A/I 9 DUE: 2015 August 30: Eric & Herman will discuss this at MIT, prepare a skeleton manuscript with example text for Suzaku XIS
  • A/I 10 DUE: 2015 August 30: Eric will compare the Henke and Verner cross-sections to see if this makes a difference for CCD instruments

 

 


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