An accuracy assessment experiment of the BRDF measured at coarse spatial resolution from space

The accuracy assessment of the Bidirectional Reflectance Distribution Funct ion (BRDF) acquired from satellite sensors at coarse spatial resolution (1 or more km) is not straightforward. One possible strategy is to compare BRD F measurements from spaceborne and airborne sensors on a test area with app ropriate characteristics of spatial homogeneity. This Letter describes an e xperiment based on this principle, aiming at the control of the BRDF measur ed by POLDER/ADEOS. The BRDF derived from the satellite data is compared wi th that derived from spatially averaged airborne POLDER data over a foreste d area of the Landes region. The magnitude and shape of the BRDF measured b y both sensors are found to be consistent within an accuracy of 0.01 in ref lectance units, except for the principal plane in the blue band where some inconsistency is found. Similar experiments could be used for the verificat ion of other sensors data, such as those of MISR and MODIS onboard Terra, a nd POLDER 2 onboard ADEOS 2 in the near future.