====== Telecon 20170919 ======


__Agenda:__ 
  * Focal Plane Model + Noise (Young) {{:pico_fdm_noise_model_status_20170919.pdf|Slides}} 
  * {{::coma-correction.pptx|Optics: coma correction (Hills)}}
  * Optics {{::cross_dragone_sep192017.pdf|Cross Dragone Designing}}(Wen)
  * {{::cbmpol_trade_interfaces.xlsx|Trade matrix}}

__Notes:__

Attending: Al, Brian, Roger, Jeff F., Julian, Shaul, Karl, Qi

Noise and focal plane (Karl Young)
  * baseline polarization weight calculated. full sky, 4 yrs.
    * accounting for DLFOV area on focal plane, not laying out wafers.
    * correction from last week's pixel count.  Now 6k (open), 10.5k (crossed)
  * Set edge taper to lowest band of MC pixel
    * pixel size up by 1.4x, N pixels down by 2, sensitivity down by 1.4
    * stop under-illuminated for higher bands in pixel
      * this means a loss of resolution compared to optimum for 1.4 m mirror
    * **General question to group**  What near sidelobe level is acceptable? -20 dB? -40 dB?  This sets the acceptable edge tapers.
  * Comparison with Roger's TDM noise
    * loading agrees
    * photon noise off by 17% at low frequency, probably Bose noise difference, investigating
    * phonon noise off by 30%, likely difference in safety factor 2 (Roger) vs 2.5 (Karl)
    * NETs, Karl higher by 30% at 20 GHz, higher by 5% at 800 GHz
      * due to where phonon noise is more significant.

Coma corrected optics (Richard Hills, presented by Shaul)
  * Dragone calculated equations to elimate coma in Dragone type systems
  * Richard implented this via computer optimization in Zemax for the open and crossed systems
  * DLFOV increases at all frequencies by,
    * ~3x diameter at 900 GHz
    * ~1.1x diameter at 25 GHz

Redesigning crossed dragone (Qi Wen)
  * Goal: avoid 'clipping' sidelobe and direct focal plane view of sky
  * Requires:
    * increase f/# to move focal plane away from secondary
    * reduce FOV, allows focal plane to move away from secondary
  * Current example has now direct view, but 2 types of 3 reflection sidelobes.
  * Design work continuing. 

Trade-off matrix (Brian)
  * trade-offs vs baselines of various aspects
  * goal is to show connections between systems
  * work in progress:
    * add spin and precession rates
    * is orbit still variable?  Or fixed to L2?