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Assessment of Satellite-Derived Surface Reflectances by NASA's CAR Airborne Radiometer over Railroad Valley, NevadaCAR (Cloud Absorption Radiometer) is a multi-angular and multi-spectral airborne radiometer instrument, whose radiometric and geometric characteristics are well calibrated and adjusted before and after each flight campaign. CAR was built by NASA (National Aeronautics and Space Administration) in 1984. On 16 May 2008, a CAR flight campaign took place over the well-known calibration and validation site of Railroad Valley in Nevada (38.504 deg N, 115.692 deg W).The campaign coincided with the overpasses of several key EO (Earth Observation) satellites such as Landsat-7, Envisat and Terra. Thus, there are nearly simultaneous measurements from these satellites and the CAR airborne sensor over the same calibration site. The CAR spectral bands are close to those of most EO satellites. CAR has the ability to cover the whole range of azimuth view angles and a variety of zenith angles depending on altitude and, as a consequence, the biases seen between satellite and CAR measurements due to both unmatched spectral bands and unmatched angles can be significantly reduced. A comparison is presented here between CARs land surface reflectance (BRF or Bidirectional Reflectance Factor) with those derived from Terra/MODIS (MOD09 and MAIAC), Terra/MISR, Envisat/MERIS and Landsat-7. In this study, we utilized CAR data from low altitude flights (approx. 180 m above the surface) in order to minimize the effects of the atmosphere on these measurements and then obtain a valuable ground-truth data set of surface reflectance. Furthermore, this study shows that differences between measurements caused by surface heterogeneity can be tolerated, thanks to the high homogeneity of the study site on the one hand, and on the other hand, to the spatial sampling and the large number of CAR samples. These results demonstrate that satellite BRF measurements over this site are in good agreement with CAR with variable biases across different spectral bands. This is most likely due to residual aerosol effects in the EO derived reflectances.
Document ID
20170008527
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Kharbouche, Said
(Mullard Space Science Lab. Dorking, United Kingdom)
Muller, Jan-Peter
(Mullard Space Science Lab. Dorking, United Kingdom)
Gatebe, Charles K.
(Universities Space Research Association Greenbelt, MD, United States)
Scanlon, Tracy
(National Physical Lab. Teddington, United Kingdom)
Banks, Andrew C.
(National Physical Lab. Teddington, United Kingdom)
Date Acquired
September 7, 2017
Publication Date
June 5, 2017
Publication Information
Publication: Remote Sensing
Publisher: MDPI AG
Volume: 9
Issue: 6
e-ISSN: 2072-4292
Subject Category
Earth Resources And Remote Sensing
Report/Patent Number
GSFC-E-DAA-TN45201
Funding Number(s)
CONTRACT_GRANT: EU-FP7 607405
CONTRACT_GRANT: NNG11HP16A
Distribution Limits
Public
Copyright
Other
Keywords
calibration
surface reflectance
airborne

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