L-3 Integrated Optical Systems/SSG designed and built the telescope, aft imager, and scanner for the Widefield Infrared
Survey Explorer (WISE) under subcontract to Utah State University/Space Dynamics Laboratory. The WISE mission
and collection scheme imparted several driving requirements on the telescope and scanner, including the need for low
cost implementation, <11 Kelvin operation, and the need to back-scan by half a degree during detector integration in
order to freeze the line of sight on the sky as the spacecraft pitched in orbit. These requirements led to several unique
design and implementation choices for the telescope and scanner. In this paper we highlight several of those design
choices as well as lessons learned from the telescope and scanner design, fabrication, and test. WISE, a NASA MIDEX
mission within the Explorers program, was managed by the Jet Propulsion Laboratory. WISE launched on December
14, 2009 and is currently operating successfully.
On December 14, 2009 NASA launched the Wide-field Infrared Survey Explorer (WISE), a NASA MIDEX mission
within the Explorers program that is currently performing an all-sky survey in four infrared bands. L-3 Integrated
Optical Systems/SSG designed, built, and tested the telescope, scanner, and aft imaging optical system for WISE under
contract to the Space Dynamics Laboratory. Hardware and test results for those subsystems are presented, as well as an
on-orbit status of their imaging performance. The WISE payload includes a 40 cm afocal telescope, a scan mirror for
back-scan during integration, and an aft optics imager assembly. All modules operate below 17 Kelvin. The allreflective
system uses aluminum mirrors and metering structures. The afocal telescope provides distortion control to
better than two parts in a thousand to prevent image blur during internal scanning. The one-axis scan mirror at the exit
pupil scans the detectors' field-of-view across the telescope field-of-regard, countering the orbital motion and freezing
the line of sight during the multi-second exposure period. The five-mirror imaging optics module follows the scan
mirror and feeds dichroic beamsplitters that separate the energy into four channels between 2.8 and 26 microns. Once
initial on-orbit checkout and calibration was completed, WISE began a 6-month mission performing an all-sky survey in
the four infrared bands, which is over 80% complete as of June 2010.
KEYWORDS: Mirrors, Silicon carbide, Mirror pointing, Polishing, Finite element methods, Servomechanisms, Line of sight stabilization, Space mirrors, Thermal modeling, Silicon
A Silicon Carbide (SiC) based wide field of view Pointing Mirror Assembly (PMA) has been developed to provide two
axis line-of-sight control for a fixed, space based imaging sensor. Thermal modeling has been completed in order to
project the excellent thermal stability anticipated from the SiC PMA, and closed loop servo testing of the hardware has
been conducted in order to quantify the bandwidth associated with line-of-sight control. In addition to the system level
testing the SiC mirror substrate itself has been tested for thermal stability. We also report on results obtained with a
novel polishing technique which has been applied in order to allow optical finishing of the two-phased Reaction Bonded
(RB) SiC mirror substrate without the need for Silicon or SiC claddings.
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