Telecon 20170919

Agenda:

• Focal Plane Model + Noise (Young) Slides (.pdf)
• Optics: coma correction (Hills) (.pptx)
• Optics Cross Dragone Designing (.pdf) (Wen)
• Trade matrix (.xlsx)

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?