SLAC-2017:Telescopes and Receiver Optics Parallel Session

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Large Aperture Telescope Optics Parallel Session

Post session talks here.

Receiver Optics & Small Aperture Telescopes Parallel Session

Post session talks here.

Notes from sessions

Action item: need to figure out some top-level specs & figures of merit for telescopes

throughput, fov

  • frequency range in array and per telescope, number of detectors vs, freq. and telescope size, bands per pixel
  • multipole coverage (what size telescope for what multipole)
  • is high throughput the right goal, do we want more smaller telescopes for ops reasons?
  • optical efficiency, Strehl

pol beam systematics

  • near & far sidelobes, smoothness of sidelobes, baffling, loading due to abortive baffles
  • pol mod? HWP location? boresight rotation?
  • spec on instrumental pol, abs value and stability?
  • how much to oversize mirrors, precision or rough surface on oversize?
  • panel gaps OK, or are we dominated by scattering from filters/windows
  • pol angle calibration, how simple with a given tel configuration

other telescope stuff

  • cost, lifetime not just parts
  • structure size, stability
  • f#, coupling to receivers
  • robustness, serviceability
  • real world vs. expected sensitivity
  • as built vs. design performance
  • uptime
  • synch with detector/receiver development

cold optics

  • component testing, e.g., scattering from filters
  • what size lenses/filters/HWPs/windows
  • how much loading? how to model this?

Requirements flow from science to telescopes

what do we need to know from sims?

sensitivity vs. f_sky and foreground level

  • feeds into site choice(s)
  • directly linked to next two issues

beam size & sensitivity vs. freq

  • min sizes of telescopes
  • number of detectors in each band on each telescope size

grouping of bands on telescopes

  • matched beams?
  • simultaneous measurements with concentric beams?

scattering & sidelobe level, stability (mechanical & thermal)

  • how to specify this
  • may benefit from 2 levels of discrimination: first, experience-informed baseline requirements to narrow down the options, and then detailed 2pi or 4pi beam maps fed into observation sims to estimate systematics of the best designs
  • may be different for each telescope type, frequency, site/scan strategy

mount requirements

  • scan speed, pattern vs. freq -- pointing & tracking requirements
  • does scan strategy need multiple, independent mounts?
  • which telescopes require boresight rotation?


  • which sources do we need to see? how often?
  • do we need planets?
  • do we need ground-based sources? towers? big temporary fold mirrors (a'la BICEP and Keck)?

Site & ops to telescopes

site specific conditions

  • temp, seismic, insolation, rain/snow

power constraints


uptime & maintainability

  • do we need several telescopes/mounts?

Requirements flow within telescopes (trade studies, allocations, good practice, prejudice)

tel size vs. ell

  • small tels for low ell?

reflectors vs. refractors

tel optical layout

tel mount layout

number of each type of telescope

shield config

can we tolerate panel gaps on big telescopes?

boresight rotation to fix tel errors?


Requirements flow to/from cameras

subfield cameras? (yes requires 1st lens at tel focus)

tel focal ratio (not necessarily same as at detectors)

limits/rqts on camera orientation/motion/accel

tel boresight rotation to fix residual camera beam/pol errors

  • instrument rotation may be easier

drive noise (EMI, vibration, magnetic)

access to camera (frequency, specific orientation)

Action items/Next steps

Summarize action items here