imagerteleconnotes20180411 [Probe Mission Study Wiki]

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====== Telecon 20180411 ======

Attending: Brian, Roger, Jeff F., Shaul, Karl, Qi

Notes by : Qi

=== Agenda===

  * {{::slides.pdf|Update on Sidelobes}}
  * Imager topics to discuss in the workshop/future
    * 1/f noise and modulator
    * ADR + Temperature stability

=== Notes ===

  * Sidelobes
    * simulation in GRASP:only mirrors and stop; no sunshield, no baffle, no cold box
    * slide 2 & 3
      * theta: 0 deg is central ray; positive is going down in the right figure
      * the peak at 0 deg in upper left is corresponding to the "north pole" in lower left
      * going from north pole straight down to south in lower left is going positive in upper left; going from north pole along the rim to south is going negative in upper left
      * -75 deg primary sidelobe
        * spillover passing the primary 
    * slide 4
      * Rejection needed; a measure of signal level
      * right side: Rejection needed below 1 um arcmin
    * slide 5
      * horizontal lines: below which the signal would be rejected. For example, the signal from galaxy would be rejected below purple line
      * vertical lines: middle red line is shield; pink and red are where moon and earth would appear
      * the area between the lines (~ -180 to ~ 40 deg) is the direct view
      * Closures are not included. Adding a closure similar to Planck, covers PR.
      * We are not going to calculate with shields at the moment. We are not sure if there will be issue. It's beyond the scope of current study.
      * Brian: one of main sidelobes could be from the bump close to focal plane, ADR. Shaul: the size of the bump has been reduced, the figure in slide 2&3 is not accurate, so it may not be a problem.
      * Moving ADR down: 1) magnetic field from SUIQD, 2) sidelobe, 3) cooling issue

  * Imager topics to discuss in the workshop/future
    * The overall instrument is reasonablly complete
    * 1/f noise and modulator
      * no modulate can accommodate with large aperture
      * not clear how 1/f might affect our low-l value
      * what are the possibilities of 1/f, what can we intelligently say about this
      * Jeff: we suggested for TeamX based on data we have, progress of tests one should do. We have a lot qualitative understandings, but at the end, we have to test it. Should be lower level than Planck. But we have never pushed to the level how does cosmic rays affect low l and 1/f.
      * Time-domain simulation can predict something sensible.
      * cosmic rays:
        * for Planck, two problems: 
          * 1)high rate
            * due to hitting not just the bolo but entire silicon
            * thermal issue, can be addressed
          * 2)long duration, high time constant
            * not 100% understood, related to heat capacity.
            * we can use data from Planck and SPIDER
            * testable
          * The combination of both makes it problematic.
      * "Would you reduce to the level that your Low-l measurement is not affected?", "What is the rate, what is the capacity to eliminate the effect?"
        * People who do simulation should be able to help, e.g. Brandon, HFI simulation. 
        * 1/f. We have some simulation from CORE, 1/f knees, we can estimate impacts on low-l are.
    * ADR + Temperature stability
      * summarize the discussion between Brandon and Shaul
      * ADR is not going be a driver, fluctuation is not going to be a driver in overall focal plane temperature stability

  * SPIE papers
    * prepare 1 week for comments
    * It would be good to have outlines for the SPIE papers.
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