Telecon Notes 20171025

Attendance: Shaul, Amy, Charles, ??

Notes by: Karl Young, UMN

• Presentations at AAS, SPIE, APS
• Fundamental Physics WG update (Raphael)
• Imager Update (Shaul)

Presentations (finalized = regular font; proposed = italics)

• AAS (January, DC): Special Session (Shaul) + Poster (Karl, Qi: UMN)
• APS (April, Columbus, OH; submit abstract by Jan. 12)
• Sutin - Candidate SPIE Abstract below (submit by Nov. 13)

The Probe of Inflation and Cosmic Origins (PICO) is a NASA-funded study of a Probe-class mission concept. The top-level science objectives are to probe the physics of the big bang by measuring the energy scale of inflation, probe fundamental physics by measuring the number of light particles in the Universe and the mass of the neutrino, to measure the reionization history of the Universe, and to understand the mechanisms of star formation, and the physics of the galactic magnetic field.

PICO will have multiple frequency bands between few tens and few hundred GHz, and will survey the entire sky, producing maps of the polarization of the cosmic microwave background radiation, of galactic dust, of synchrotron radiation, and of various populations of point sources.

To implement the mission we considered several instrument configurations, optical systems, cooling architectures, and detector and readout technologies. We describe the current design of the mission and describe several of our trade studies leading to this design.

Spectrometer tradeoffs full discussion in 1 week. Some current comments:

1. ?
2. CL: proposing what is essentially 2 missions doubles the work. if goal is probe funding line, maybe this isn't appropriate.
3. Amy: 50 pages for 2 missions is too short. Need to do 2 reports or ask to be able to submit extra pages. Studying both costs more.
   1. CL: This is really 2 totally seperate missions, should do 2 reports. Especially if making the case to establish a probe line.
   2. Shaul: Steering committee sentiment: Proposing 2 missions when asked for 1 would distract panel. They suggest focus on 1 you can do well.
4. Shaul(steering committee): Decadal panel will see broad range of science, so reach out to broad community for PICO.
   1. Lyman: if proposal similar to EPIC and last decadal; are we doing anything new? do we need to?
   2. budget: do we assume scientists at NASA centers or Universities?
      1. some at NASA, mission ops, but most science team at universities.
      2. CL: Important to maintain 1 location with critical mass of science team. Not single members at 30 institutions. For Planck mass was at JPL, and hardware was there as well.

Presentaitons at conferences:

1. AAS Jan. 2018 special session.
   1. Shaul giving 10 min talk.
   2. poster on optics for probe? (1-2 UMN students)
      1. UMN will circulate abstract. A/I
   3. Amy: other probes have some posters planned
2. APS April, abstacts due Jan 12.
   1. currently no presentations.
   2. could send student with poster, or someone with talk.
   3. Other probes presenting? Shaul to check with Rita. Amy check with JPL. A/I
3. SPIE summer 2018, Brian proposing an abstract, see above. A/I send comments.

Imager update:

• Large aperture, arrays of multi-chroic bolometers.
• work has been on optics, scan angles, focal plane model.
• Scan is by spin and precession, alpha and beta angles define scan.
• 2 small aperture (50 cm) 2 large aperture (120*140 cm) developed. (see slide 4)
• 2 Open, 2 crossed dragones.
  • reminder: cross dragones have sidelobes and focal plane view of sky. baffling challenges.
    • open systems are well baffled.
• Noise levels calculated for all cases.
• range of 3000-15000 detectors, if mirrors are optimized shapes. Depends on choices of optimization and pixel format.
  • Amy: optimizaiton details?
    • Dragones are coma dominated.
    • mirror surfaces are deformed to reduce coma.
    • gain DLFOV, and therefore more detectors can fit on focal plane.
  • optimized focal plane is rougly 60×80 cm.
    • Amy: will push on cooling, but may be doable.
• Amy: surface accuracy of mirrors?
  • Shaul: lambda/15 is nominal.
• 50 cm is 3x loss in FWHM vs 140 cm.
• Kris simulated scans:
  • currently at 22 and 73 degrees. not optimal.
  • Julian has taken lead in planning more detailed simulations.
  • Amy: Consider trading aperture diameter for scan angles? Shaul: Yes. get 7 deg for .2 meter of aperture.
    • science trade-off continuing. loss is 'mild' for 1.4 –> 1.2.
      • not clear this is necessary.
• Future:
  • JPL working on telescope architecture and cost.
  • Imager is fairly ready for Team X.
  • Jamie suggests we go to Team X with quotes in hand.
    • Amy: this is being worked on. Will also have 2nd meeting with Team X to revise specific assumptions.
  • Imager group will look at scan, data rates, detector distribution, systematics in simulations, GRASP? (likely not)
    • CL: don't need GRASP yet. Beyond the scope of this report.
    • Amy: Appropriate level to address systematics? Don't want to overspend resources, but want to address readers' concerns.
      • systematics and risk factors in process (Brendon). nearly done. Plan is to combine their inputs with Imager group.
      • study highest risk (as defined by Brendon's group) first. Shaul-Brendon to meet during JPL visit to address details.
    • Shaul: largest item to face in decadal, complimentary with ground, given S4.
      • CL: probe succeeds only if more ambitious than ground. S4 demonstrates limits from ground. Include what is unreachable from ground, foregrounds and frequency coverage. S4 gets to r=0.001, but below S4 can't address foregrounds and will have systematics issues. PICO should go for r = 0.0001. PICO can do reionization bump and tau, also not doable from ground.
      • Shaul: agree.
        • also in foregrounds telecon. w/Josquin et. al.
          • if r = 0, get large bias, 0.005. So does LITEBird.
          • foregrounds challenging on full sky. S4 does slightly better since on small patch.
          • CL: also saw simulations with bias (in S4).
          • CL/Shaul: foregrounds aren't figured out.
      • CL: foregrounds needs to be in next steps. Part of mitigating future uncertainties. Optimizing bands and angular resolution are issues. example: small scale synchrotron for S4.
        • Shaul: Josquin and foregrounds simulations is seperate group.
          • Dec. foregrounds workshop is part of this.
      • CL: best approach is to focus on complementarity with S4, not exclusivity.
    • Shaul: working to get Al's panel reviews of PIXIE.
    • CL: what r level is being discussed?
      • Shaul: for most sensitive case. sigma_r ~ 1-5 x 10^-4. Raphael will give details.
        • CL: this is good. Space can be more aggressive in goals.
        • this type goal will be costly, but must make science work.
    • CL: also might need better resolution at low frequency foregrounds.