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Temperature Knowledge and Model Correlation for the Soil Moisture Active and Passive (SMAP) Reflector MeshNASA's Earth observing Soil Moisture Active & Passive (SMAP) Mission is scheduled to launch in November 2014 into a 685 km near-polar, sun synchronous orbit. SMAP will provide comprehensive global mapping measurements of soil moisture and freeze/thaw state in order to enhance understanding of the processes that link the water, energy, and carbon cycles. The primary objectives of SMAP are to improve worldwide weather and flood forecasting, enhance climate prediction, and refine drought and agriculture monitoring during its 3 year mission. The SMAP instrument architecture incorporates an L-band radar and an L-band radiometer which share a common feed horn and parabolic mesh reflector. The instrument rotates about the nadir axis at approximately 15 rpm, thereby providing a conically scanning wide swath antenna beam that is capable of achieving global coverage within 3 days. In order to make the necessary precise surface emission measurements from space, a temperature knowledge of 60 deg C for the mesh reflector is required. In order to show compliance, a thermal vacuum test was conducted using a portable solar simulator to illuminate a non flight, but flight-like test article through the quartz window of the vacuum chamber. The molybdenum wire of the antenna mesh is too fine to accommodate thermal sensors for direct temperature measurements. Instead, the mesh temperature was inferred from resistance measurements made during the test. The test article was rotated to five separate angles between 10 deg and 90 deg via chamber breaks to simulate the maximum expected on-orbit solar loading during the mission. The resistance measurements were converted to temperature via a resistance versus temperature calibration plot that was constructed from data collected in a separate calibration test. A simple thermal model of two different representations of the mesh (plate and torus) was created to correlate the mesh temperature predictions to within 60 deg C. The on-orbit mesh temperature will be predicted using the correlated analytical thermal model since direct measurements from in-situ flight thermal sensors are not possible.
Document ID
20160008227
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Mikhaylov, Rebecca
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Dawson, Douglas
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Kwack, Eug
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
July 1, 2016
Publication Date
July 13, 2014
Subject Category
Earth Resources And Remote Sensing
Communications And Radar
Spacecraft Design, Testing And Performance
Report/Patent Number
ICES-2014-245
Meeting Information
Meeting: AIAA International Conference on Environmental Systems (ICES)
Location: Tucson, AZ
Country: United States
Start Date: July 13, 2014
End Date: July 17, 2014
Sponsors: International Conference On Environmental Systems, Inc.
Distribution Limits
Public
Copyright
Other

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