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Thermal stability of a 4 meter primary reflector for the Scanning Microwave Limb Sounder

Show simple item record Cofield, Richard Kasl, Eldon P. 2010-08-09T16:23:39Z 2010-08-09T16:23:39Z 2010-06-24
dc.identifier.citation Earth Science Technology Forum 2010, Arlington, Virginia, June 22, 2010. en_US
dc.identifier.clearanceno 10-1791
dc.description.abstract We 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 ∼1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over ±65◦ azimuth. The antenna 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]◦ 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 0.21μm rms/◦C, which meets SMLS requirements. en_US
dc.description.sponsorship NASA/JPL en_US
dc.language.iso en_US en_US
dc.publisher Pasadena, CA : Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2010. en_US
dc.subject tropospheric processes en_US
dc.subject Thermal stability tests en_US
dc.subject flight readiness en_US
dc.title Thermal stability of a 4 meter primary reflector for the Scanning Microwave Limb Sounder en_US
dc.type Preprint en_US

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