RADIOMETRIC MEASUREMENT COMPARISON USING THE OCEAN COLOR TEMPERATURE SCANNER (OCTS) VISIBLE AND NEAR-INFRARED INTEGRATING SPHERE

As a part of the pre-flight calibration and validation activities for the Ocean Color and Temperature Scanner (OCTS) and the Sea-viewing Wid e Field-of-view Sensor (SeaWiFS) ocean color satellite instruments, a radiometric measurement comparison was held in February 1995 at the NE C Corporation in Yokohama, Japan. Researchers from the National Instit ute of Standards and Technology (NIST), the National Aeronautics and S pace Administration/Goddard Space Right Center (NASA/GSFC), the Univer sity of Arizona Optical Sciences Center (UA), and the National Researc h Laboratory of Metrology (NRLM) in Tsukuba, Japan used their portable radiometers to measure the spec tral radiance of the OCTS visible and near-infrared integrating sphere at four radiance levels. These four levels corresponded to the configuration of the OCTS integrating spher e when the calibration coefficients for five of the eight spectral cha nnels, or bands, of the OCTS instrument were determined. The measureme nts of the four radiometers differed by -2.7 % to 3.9 % when compared to the NEC calibration of the sphere and the overall agreement was wit hin the combined measurement uncertainties. A comparison of the measur ements from the participating radiometers also resulted in agreement w ithin the combined measurement uncertainties. These results are encour aging and demonstrate the utility of comparisons using laboratory cali bration integrating sphere sources. Other comparisons will focus on in struments that are scheduled for spacecraft in the NASA study of clima te change, the Earth Observing System (EOS).