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Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Skukuza and Mongu SitesThe Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF (bidirectional reflection function) measurements were obtained over different natural surfaces and ecosystems in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS (Earth Observing System) satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 S, 31.5 E) and Mongu tower, Zambia (15.4 S, 23.3 E). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 microns), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 microns). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of approximately 20 degrees and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and with a 1 degree IFOV, the pixel resolution is about 10 m at nadir and about 270 m at an 80 degree viewing angle from the CAR.
Document ID
20010106399
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Gatebe, C. K.
(Maryland Univ. Baltimore County Catonsville, MD United States)
King, Michael D.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Arnold, G. T.
(Emergent Informational Technologies, Inc. Vienna, VA United States)
Li, J. Y.
(Emergent Informational Technologies, Inc. Vienna, VA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Subject Category
Geophysics
Meeting Information
Meeting: SAFARI 2000 First Data Workshop
Location: Siavonga
Country: Zambia
Start Date: August 28, 2000
End Date: August 31, 2000
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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