Telecon 20170919

Agenda:

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?