Telecon 20171031

Attending: Brian, Shaul, Karl, Brendon, Qi, Joy, Al, Jamie

Agenda:

• Higher throughput optics, lower noise focal plane (Young)
• Scan optimization + simulations
• Orbit radius issues:
• Noise + systematics simulations

Higher throughput, lower noise optics and focal plane (Young)

• correcting optics for coma
• get to 7350 bolos or 15030 bolos (depends on pixel size and edge taper)
• pixel size set by middle band or lowest band.
  • middle band gives smaller pixels, worse spillover efficiency.
  • Brendon: far sidelobes a systematic concern. Can we estimate what these might be?
• alternative pixel band structure (slide 5)
  • reduces spillover variance within a pixel. Not clear this is a major problem.
  • NET penalty, narrow bands to avoid overlap.
    • Jamie: not clear that overlap is a problem. As long as band shapes are known.
  • Jamie: what does single band pixels look like? Fewer broad bands.
    • A/I Karl to check.
• Technical or science issues with alternative band structure?
  • nothing from people currently.

Scan optimization + simulations (Kris presentation by Shaul)

• single detector, alpha = 22, beta = 75
• was at 3 rpm spin, now 1 rpm spin, varying precessions
• suggests precession < 10 hrs
• alpha, beta dictate large scale features
• Zoom on N_obs panel, shows striping at < 12 hours.
• Jamie: pixelization effects? are there gaps in scan on small scales? Shaul: plan to do detailed scans next, w/Julian.
• rings on sky in 1 day, full maps per detector in 6 months.
• Jamie: thinks no resource problems with fast precession.
  • Still need check with Amy.
• Aside: Brendon, adding reaction wheels to systematics. Can have vibrations.
  • Jamie: Can have 'momentum wheel' to balance total spacecraft momentum and take load off reaction wheels.

Systematics, simulations, noise:

• How to combine systematics and imager work?
• Brendon: Systematics WG has list of systematics and risk level for each. Goal to prioritize systematics.
  • table on wiki. SRF rating of 5 is worst.
  • Most worried: Far sidelobes, gain stability, pol angle calibration.
    • combination of we know least about it, drives instrument design, or limited past experiments
  • others also, but more confident they can be dealt with.
  • WG has found simulation capability, e.g. TOAST.
    • Shaul: TOAST was plan to simulate noise + scan.
    • systematics can be added here as well. Work done for LITEBird, CORE.
    • example: adding far sidelobes is straightforward
    • T–>P leakage sim by CORE.
      • QuickPol looks at main beam mismatch.
      • bandpass mismatch (Ranajoy)
      • in CORE systematics paper. They are able and interested.
  • Joy: many simulations give you large values for systematics, but they will be partially removed by analysis. This needs to be considered. Brendon: Yes, TOAST has this type of analysis tool built in. Needs to be kept in mind.
• Jamie: Good approach. Don't worry about everything, priortize based on Planck, CORE, LITEBird work.
• Shaul: Goal, get inputs systematics group needs.
  • far sidelobes, working on input via Brad and Amy
  • polarization calibration inaccuracies: Initial calibration. Errors on calibration. Dependence on spectrum used to calibrate, or dependence on source observed
    • no solid calibration plan yet, so key errors not yet known or quantified. (not ready for simulation)
  • gain stability: ability to continuously measure gain. 4 yr calibration on dipole is great. But can't see dipole constantly (scan strategy input). CORE folks have worked on this, Tomassi volunteered but not until January.
    • Joy: need instrument inputs on gain stabiliy (bath, temperature variation, etc.)
      • can simulate observation, calibration on dipole with scan, quantify how well this can be done.
    • Jamie: can this simulate deprojection? It is very useful. Brendon: Planck had dipole S/N > degree scale S/N, so not useful. Could be better this time around.
      • not clear this capability exists.
• Brendon, Shaul, Joy to meet this week and coordinate on systematics plan.