private:teleconsnotes20171018 [Probe Mission Study Wiki]

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====== Telecon Notes 20171018 ======

Attendance:  Shaul, Dave Chuss, Amy, Julian, Lloyd, Nick Battaglia, Charles, Brendon\\

Notes by:  Karl (UMN)

=== Agenda ===
  * periodic update comments
  * Spectrometer / Imager trade-off discussion. Today's focus is receiving updates from the {{:private:sf_and_diffuse_ism_case_2017oct13.pdf|galactic}}, and [[https://docs.google.com/document/d/1HgoAafL4NwJDCTE0fCKQudgXWZtHx6EQU9K-oWm9xvs/edit|extragalactic]], and fundamental physics group as they pertain to the question of the trade-off. [[https://zzz.physics.umn.edu/ipsig/spectrometeroptions|The spectrometer science white paper is posted here.]]

Periodic Comment Text: 

Hello Space Probe Enthusiast,

Here is an update on the progress of the Probe of Inflation and Cosmic Origins (PICO) (aka the CMB Probe) mission study. An expanded version of this update, including more details, is available on our wiki site.

Foregrounds Workshop

The mission study is sponsoring a 3-day Foregrounds workshop in the University of California San Diego. The dates are Nov. 29 (Wednesday), Nov. 30 (Thursday), and Dec. 1 (Friday), 2017. Please mark your calendars. These dates are a change relative to our previous announcement, but they are more convenient for the vast majority of attendees. For travel purposes, the workshop will begin around 9 am on Wednesday and will end in the early afternoon of Friday. Please register now.

Spectrometer and Imager

The spectrometer group compiled a white paper describing a spectrometer to be added to PICO. The white paper, as well as other material from the group are posted on the wiki. The JPL mission study lead told the Executive Committee (EC) that including a spectrometer will require reduction in the cost of the imager, which translates to a smaller instrument with smaller focal plane. The imager group has developed an imager option with 0.5 m aperture, a factor of 2.8 smaller than the baseline design.

The EC has invited studies from other working groups (Fundamental Physics, Extragalactic Science, Galactic Science) to assess the science trade-offs from a mission consisting of only a 1.4 m aperture imager compared to a 0.5 m aperture imager and a spectrometer. The contributions from these WG are available from the respective coordinators and are mostly posted on the wiki page.

The EC expects a decision by the end of October. You are invited to look at the available documents and provide your thoughts on this issue to any of the EC members.

TeamX Design and Costing

The first detailed design and costing session will be held at JPL in mid-December. This will be an important milestone and will provide a check on our baseline designs. The design of a 1.4 m aperture imager is reasonably mature, as detailed on our wiki pages. There are however still opportunities to contribute through the weekly telecons of the imager group.  The design of a joint spectrometer and imager mission will require additional development should we decide to pursue this option.

Science Working Groups

The Fundamental Physics, Extragalactic, and Galactic Science groups continue to clarify the science deliverables from PICO. You are invited to participate in their assessment and forecasting work. Please attend the telecons or contact the coordinator.

Conferences, Workshops

- Shaul discussed PICO and its complementarity with CMB-S4 during the August 2017 workshop at Harvard.
- PICO will be on display at the AAS meeting in January. There will be a 10 min talk during a 90 min special session dedicated to reviewing all 8 NASA Probe Mission Studies. 

=== Notes ===

Decision on imager and spectrometer delayed to 2 wks from today.

periodic update comments   
  * paragraph 3 of Spectrometer and Imager: remove text in []'s.  There are likely > 2 options.

Spectrometer/Imager trade-off discussion
  * Dave: Galactic trade-offs, 30K 140cm vs 4K 50cm
    * more detail than needed here, WG document
    * ultimate goal: resolve magnetic field from ISM to star formation scales and connect to high res telescopes, eg ALMA.
    * Goal 1: resolve HI to HII transition in clouds (magnetic field connection between cloud and ISM)
      * Both systems work.  4K slightly better.  Not resolution limited.
    * Goal 2: stellar cores in molecular clouds.  Sensitivity is no challenge.
      * resolution is key. resolve cores and filaments.  See magnetic fields and star formation in situ.
      * Planck got to 5', so 3' with 50 cm is small improvement.
        * want 0.1 pc resolved.
        * need beams < 2 arcmin.
        * loose all clouds for 50cm case.
        * not frequency driven, just need resolution.
        * BLASTPol is can do similar science.  **A/I** Dave: check what BLASTPol can do.  How this compares?
    * Goal #3.  map  mag field.  seeing clouds out to kpc.  how many resolve 1 pc scales?
      * again resolution limited, not sensitivity
      * 1' --> 700 clouds. 3.4 kpc away.
      * 3' --> 60 clouds.  1.4 kpc away.  survey less of galaxy.
    * 4: Polarization spectrum.
      * grain alignment and dust (John valincourt)
      * 4K may do slightly better.
    * 5: Mag field in other galaxies.
      * resolution limited. need 10 beams across galaxy
      * group excited about this, a real statiscal sample (100) at 1'.
        * gets beyond local group if 1'   
    * 6: Diffuse ISM
      * physics and properties of dust.  Closest tie to CMB foregrounds
      * target with lowest flux, ~10x lower than molecular cloud envelopes
      * see turbulence power spectrum and field strength.
      * need < 4' beams
      * sensitivity is needed. 0.5 MJy/sr
        * 4K sensitivity is big gain. get to 1% on 3' scales.
        * 30K gets to ~ 7% polarized dust at 10' smoothed.
      * assuming 2 component dust, different polarization fractions. both at 3'
        * 30K error is 10's of %.
        * 4K error is 1%
    * Overall:
      * Sensitivity limits diffuse ISM, only that.
      * Resolution gains are molecular cloud science.
      * Dave's overall guess: Resolution is of more interest to community. Not unanimous.
      * Shaul: Will need to translate this to broad science case. To present to broad non-expert community. Do offline.

  * Nick: Extragalactic science.
   * Cluster cosmology (neutrino masses, w, wa):
     * resolution of 50cm loses ~1/4 of clusters. From thermal SZ.
     * if S4 exists, this has no real science impact.
       * real PICO benefit is in tau measurement
     * no S4, 15-20% hit in measurement
   * CMB lensing S/N:
     * PICO is good lensing experiment, comparable to S4, if 1.4m
     * simplest assumptions: no foregrounds, perfect delensing.
     * better simulations are now set up.
   * CMB halo lensing (cluster masses).  50cm gives loss of 2-3x in mass sensitivity
     * larger beam (50cm) incorporates 2-halo term, so likely even more uncertainty.
   * y-map cleaned S/N.  numbers need to be rechecked.
   * Extragalatic point sources: largest loss at 50 cm.  Still qualitative estimates.
     * 140cm find 3000 sources where Planck found 10.
     * 50cm, worse than Planck.
   * Polarized point sources: can add confusion to r determination. 140cm mission informs on this. 50cm adds nothing new.
   * Proto clusters: 140cm, image 1000's (dusty star forming galaxies). 50cm sees none.
   * Reionization with S3 ground based.
     * both (50 and 140 cm) give good tau, and midpoint of reionization.
 
   * Charles: all this wants more resolutions. This is done well from ground.  Not going to get more resolution than 1.4m. If all sky or high frequency helps a measurement space is appropriate.  We should emphasize distinctions between ground/space. Also emphasize complementary.
   * Nick: space gets higher frequencies. So helps dusty galaxies and CIB mitigation.

Jamie via Shaul:  Jamie concerned: 140-50 cm trade-off may not be needed.  Smaller aperture may not be the cost saver. Maybe the right descope is to reduce FP size or #channels, #readout, power draw.
  * Charles:  doing imager + spectrometer will compromise both.  The trade-offs may vary, not necessarily mirror size, but trade-offs exist. Should do both as 2 separate satellites. Both are large, complex, difficult advances and warrant their own missions.
  * Jamie: -- thru Shaul -- do everything we can from space.
  * Lloyd: Concerned that if we combine both, it is a case against Probe mission for either.
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