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Proceedings Paper

Ground comparisons at RadCalNet sites to determine the equivalence of sites within the network
Author(s): Tracy Scanlon; Claire Greenwell; Jeffrey Czapla-Myers; Nikolaus Anderson; Teresa Goodman; Kurt Thome; Emma Wolliams; Geiland Porrovecchio; Petr Linduška; Marek Šmíd; Nigel P. Fox
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Paper Abstract

The Radiometric Calibration Network (RadCalNet, www.radcalnet.org) routinely brings together data from several instrumented ground sites to provide users with top-of-atmosphere (TOA) reflectance data. These data are provided on cloud free days between 09:00 and 15:00 for the spectral range 400 to 1000 nm (and up to 2500 nm depending on available instrumentation) at a 10 nm spectral resolution. The data represents the nadir view of the ground. A key aspect to RadCalNet is a strict adherence to SI-traceability leading to well-understood and defensible uncertainty analysis to ensure that the different sites operating within RadCalNet are consistent with one another. This process includes the requirement to validate uncertainty analyses. One way in which this can be achieved is through field-based comparisons between independently measured reflectance of the ground and the RadCalNet data product for that date / time. To test the potential of such comparisons for uncertainty validation, a comparison campaign has been un- dertaken by the UK’s National Physical Laboratory (NPL) with the University of Arizona (UA) in March 2017 at the Railroad Valley radiometric test site in Nevada, USA using instruments developed for the purpose by UA and the Czech Metrology Institute (CMI). The measurements taken at the site with a new instrument, the Multispectral Transfer Radiometer (MuSTR) have been compared against the RadCalNet bottom-of-atmosphere (BOA) dataset to determine the equivalence of the reflectance. Radiances from MuSTR have also been compared against radiance measurements from the in-situ instrumentation at the site using a 48 % reflectance tarpaulin as a target. The comparisons presented here have demonstrated the utility of field-based comparisons for RadCalNet. In addition, a potential methodology for these comparisons has been developed and potential areas for improvement, including the systematic development of field-based uncertainty analyses, have been identified.

Paper Details

Date Published: 29 September 2017
PDF: 13 pages
Proc. SPIE 10423, Sensors, Systems, and Next-Generation Satellites XXI, 104231B (29 September 2017); doi: 10.1117/12.2278649
Show Author Affiliations
Tracy Scanlon, National Physical Lab. (United Kingdom)
Claire Greenwell, National Physical Lab. (United Kingdom)
Jeffrey Czapla-Myers, College of Optical Sciences, The Univ. of Arizona (United States)
Nikolaus Anderson, College of Optical Sciences, The Univ. of Arizona (United States)
Teresa Goodman, National Physical Lab. (United Kingdom)
Kurt Thome, NASA Goddard Space Flight Ctr. (United States)
Emma Wolliams, National Physical Lab. (United Kingdom)
Geiland Porrovecchio, Czech Metrology Institute (Czech Republic)
Petr Linduška, Czech Metrology Institute (Czech Republic)
Marek Šmíd, Czech Metrology Institute (Czech Republic)
Nigel P. Fox, National Physical Lab. (United Kingdom)


Published in SPIE Proceedings Vol. 10423:
Sensors, Systems, and Next-Generation Satellites XXI
Steven P. Neeck; Jean-Loup Bézy; Toshiyoshi Kimura, Editor(s)

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