====== Telecon 20180221 ======

Attending: Tom, Tomo, Toki, Brian, Kris, Shaul, Karl, Qi

Notes by : Qi \\

=== Agenda===

  * Attitude Control and Reconstruction Requirements (Wrap up)
    * Tentative baseline: control = 1' (3 sigma) over 1 spin period; reconstruction = 1" (3 sigma) 
    * Last week's presentation from Jacques: [[https://zzz.physics.umn.edu/ipsig/_media/systematicswg/telecons/2018-02-14/pointing.pdf|Attitude control requirements (Jacques)]]
    * Last week's images from Kris:  | {{::m000.png?100|m000.png}} | {{::m000ge.png?100|m000ge.png}} | {{::m000gm.png?100|m000gm.png}} |
    * {{::precession_fast_slow.pdf|Kris' update for this week }}
  * Telescope I+T (Tomo and Bill)
    * {{::20171212_picoi_t_v002.pdf|Tomo's slides}}
    * {{::plancki_t_jones_20171212.pdf|Receiver, Bill Jones}}
  * Instrument I+T (Bill J.)

=== Notes ===
  * Attitude Control and Reconstruction Requirements (Wrap up)
    * The discussion was from last week: based on cross scan sampling, Jacques argued that increasing precession period T_prec is an potential solution, in order to achieve better sky coverage
    * Kris did not agree
    * Kris's updates:
      * figures show the high-resolution (highest frequency beam) hits number of sky coverage, assuming precession angle 30 deg and spin spin angle 65 deg.
      * Two cases were studied, fast (48 hrs) and slow (7 hrs)
      * it's shown that hits are dense on the edge of "donuts", and coarse in the middle
        * for slow precession, the distinction between edges and inner parts is more obvious
      * color is in log scale, red is much more dense than blue
      * color scales in slow and fast are not same; the maxium in 48 hrs is a factor of ~4 compared to 7 hrs
      * Kris's conclusion: short (fast) precession is better
    * Shaul: 1 arcmin in 3 sigma in single spin rate is based on fast precession
    * Kris: many motions of PICO are much faster than Planck, we need to be careful. Someone studing WMAP pagers is a good thing to do.
    * Shaul: we need to be careful, star tracker; In optical astronomy, they don’t scan fast, so it’s trivial for them.




  * Telescope I+T (Tomo）
    * pg24
      * reminder, introduction about what Tomo talks today
      * fully integrated test when it’s cold
      * optics only; tests one can possibly imagine
    * pg28
      * purpose: mirror shape 
      * two spacial scales: large ,small scales
        * Large scals: you cannot probe smaller than the space between markers
        * Short scales: very small scales
      * A combination of both scales; blue table
      * “Cold” means some cold temperature, not necessary the mission temp
      * Minimal tests for PICO: Photogrammetry and Interferometry; certainly can be done
      * CMM: surface, not sure if there is facility big enough for PICO mirror
      * Shaul: mirror vendor, whatever lab who puts the instrument together; whoever provides mirrors, they would CMM warm; CMM is part of the cost buying the mirror; I & T is beyond vendor level.
      * Tomo: for space mission, it’s common you repeat measurements even vendors have done so.
      * Brian: normally,  vendors verify, we would not check again.
      * Tomo: different models, e.g. ground model, flight model; you can do tests in first few models, then you trust (vendors).
    * pg29
      * Tomo: partly a comment, partly a question
        * after the characterization, what information are we using?
      * pre-flight: sub and full level tests; outputs: performance verification and mirror shapes
      * inflight: beam calibration; slide shows beam profile from Planck
      * post-flight: if with precise beam, with pre-flight information, systematics; if beam not precise, we need GRASP model, and correct for it.
      * What did Planck use to get beam? What are the key information?
      * Kris: LFI used Grasp model; HFI used planet measurements; signal-to-noise is the reason. LFI is much more noisy. Absolute size of beam matters. pre-flight + inflight consideration.
      * Beam size is important because couple to focal plane; in part of scanning. Sometimes more reliable on GRASP model.
      * Tomo: future mission should have tighter requirement for signal-to-noise; does this mean they will be like LFI case?
      * Kris: Any test before flight is valuable.  
      * Shaul: not clear what Planck did was used and useful in terms of tests.
      * Kris: not sure if there is a short path compared to Planck.
    *Pg30
      * Tomo: it’s very important to characterize feed beam. For Planck, corrugated horns are classic and thus did not need more attention; PICO could use something else.