NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb SounderThe Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission in [180,680] GHz. SMLS, planned for the NRC Decadal Survey's Global Atmospheric Composition Mission, uses a novel toric Cassegrain antenna to perform both elevation and azimuth scanning. This provides better horizontal and temporal resolution and coverage than were possible with elevation-only scanning in the two previous MLS satellite instruments. SMLS is diffraction-limited in the vertical plane but highly astigmatic in the horizontal (beam aspect ratio approx. 1:20). Nadir symmetry ensures that beam shape is nearly invariant over plus or minus 65 deg azimuth. A low-noise receiver FOV is swept over the reflector system by a small azimuth-scanning mirror. We describe the fabrication and thermal-stability test of a composite demonstration primary reflector, having full 4m height and 1/3 the width planned for flight. Using finite-element models of reflectors and structure, we evaluate thermal deformations and optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during soak tests in a chamber. The test temperature range exceeds predicted orbital ranges by large factors, implying in-orbit thermal stability of 0.21 micron rms (root mean square)/C, which meets SMLS requirements.
Document ID
20150006781
Document Type
Conference Paper
External Source(s)
Authors
Cofield, Richard E. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Kasl, Eldon P. (Vanguard Space Technologies, Inc. San Diego, CA, United States)
Date Acquired
April 27, 2015
Publication Date
August 20, 2011
Subject Category
Structural Mechanics
Instrumentation and Photography
Meeting Information
SPIE Optics + Photonics 2011 Conference(San Diego, CA)
Distribution Limits
Public
Copyright
Other
Keywords
thermal distortion
toroidal
microwave limg sounding
composite reflectors
physcial optics