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Proceedings Paper

SWIR calibration of Spectralon reflectance factor
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Paper Abstract

Satellite instruments operating in the reflective solar wavelength region require accurate and precise determination of the Bidirectional Reflectance Factor (BRF) of laboratory-based diffusers used in their pre-flight and on-orbit radiometric calibrations. BRF measurements are required throughout the reflected-solar spectrum from the ultraviolet through the shortwave infrared. Spectralon diffusers are commonly used as a reflectance standard for bidirectional and hemispherical geometries. The Diffuser Calibration Laboratory (DCaL) at NASA's Goddard Space Flight Center is a secondary calibration facility with reflectance measurements traceable to those made by the Spectral Tri-function Automated Reference Reflectometer (STARR) facility at the National Institute of Standards and Technology (NIST). For more than two decades, the DCaL has provided numerous NASA projects with BRF data in the ultraviolet (UV), visible (VIS) and the Near InfraRed (NIR) spectral regions. Presented in this paper are measurements of BRF from 1475 nm to 1625 nm obtained using an indium gallium arsenide detector and a tunable coherent light source. The sample was a 50.8 mm (2 in) diameter, 99% white Spectralon target. The BRF results are discussed and compared to empirically generated data from a model based on NIST certified values of 6°directional-hemispherical spectral reflectance factors from 900 nm to 2500 nm. Employing a new NIST capability for measuring bidirectional reflectance using a cooled, extended InGaAs detector, BRF calibration measurements of the same sample were also made using NIST's STARR from 1475 nm to 1625 nm at an incident angle of 0° and at viewing angle of 45°. The total combined uncertainty for BRF in this ShortWave Infrared (SWIR) range is less than 1%. This measurement capability will evolve into a BRF calibration service in SWIR region in support of NASA remote sensing missions.

Paper Details

Date Published: 3 October 2011
PDF: 11 pages
Proc. SPIE 8176, Sensors, Systems, and Next-Generation Satellites XV, 81760W (3 October 2011);
Show Author Affiliations
Georgi T. Georgiev, Sigma Space Corp. (United States)
James J. Butler, NASA Goddard Space Flight Ctr. (United States)
Catherine Cooksey, National Institute of Standards and Technology (United States)
Leibo Ding, Sigma Space Corp. (United States)
Kurtis J. Thome, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 8176:
Sensors, Systems, and Next-Generation Satellites XV
Roland Meynart; Steven P. Neeck; Haruhisa Shimoda, Editor(s)

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