Initial results of the bidirectional reflectance characterization round-robin in support of EOS

Laboratory measurements of the bidirectional reflectance distribution funct ion (BRDF) of diffusely reflecting samples are required to support calibrat ion in the Earth Observing System (EOS) programme of the National Aeronauti cs and Space Administration (NASA). To assess the ability of the instrument calibration laboratories to perform accurate BRDF measurements, a round-ro bin comparison with the National Institute of Standards and Technology (NIS T) as the central laboratory was initiated by the EOS Project Science Offic e. The comparison parameters, which include measurement wavelength, spectra l bandwidth, illumination and viewing geometry, sample type and alignment, and data format, were selected in consultation with the participants. The p articipants were selected based on their roles as metrology laboratories wi th direct connections to EOS or other international Earth remote-sensing sa tellite programmes. This paper briefly describes the format of the comparis on, the status of the first round, and some preliminary results.