====== Telecon 20171031 ======

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

__Agenda:__ 

   * {{::optimizing_baseline_20171031.pdf|Higher throughput optics, lower noise focal plane}} (Young)
   * {{::probe_scanning_20171031.pdf|Scan optimization + simulations}}
   * Orbit radius issues: {{::screen_shot_2017-10-31_at_1.50.35_pm.png?50}}
   * Noise + systematics simulations

=== Notes ===

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.