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Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb SounderWe describe the fabrication and thermal-stability analysis and test of a composite demonstration model of the Scanning Microwave Limb Sounder (SMLS) primary reflector, having full 4m height and 1/3 the width planned for flight. SMLS is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 660 GHz. Current MLS instruments in low Earth orbit scan pencil-beam antennas (sized to resolve about one scale height) vertically over the atmospheric limb. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, adds azimuthal scanning for better horizontal and temporal resolution and coverage than typical orbit spacing provides. SMLS combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but highly astigmatic in the horizontal, having a beam aspect ratio [tilde operator]1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over +/-65(white bullet) azimuth. The a feeds a low-noise SIS receiver whose FOV is swept over the reflector system by a small scanning mirror. Using finiteelement models of antenna reflectors and structure, we evaluate thermal deformations and the resulting optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during wide-range (ambient+[-97,+75](white bullet) C) thermal soak tests of the primary in a chamber. This range exceeds predicted orbital soak ranges by large factors, implying in-orbit thermal stability of 0.21(mu)m rms/(white bullet)C, which meets SMLS requirements.
Document ID
20100031298
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Cofield, Richard
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Kasl, Eldon P.
(DR Technologies, Inc. San Diego, CA, United States)
Date Acquired
August 25, 2013
Publication Date
June 24, 2010
Subject Category
Spacecraft Design, Testing And Performance
Meeting Information
Meeting: Earth Science Technology Forum 2010
Location: Arlington, VA
Country: United States
Start Date: June 22, 2010
Distribution Limits
Public
Copyright
Other
Keywords
Thermal stability tests
flight readiness
tropospheric processes

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