Publication Date:
2016-01-09
Description:
We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider , a polarization-sensitive balloon-borne telescope array that observed the cosmic microwave background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of ±0.1 ∘ . The system performed well in Spider during its successful 16 day flight.
Print ISSN:
0034-6748
Electronic ISSN:
1089-7623
Topics:
Electrical Engineering, Measurement and Control Technology
,
Physics
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