干旱区生态环境知识资源中心

The performance of the on board calibrator for bands 1 (approximate to0.66 mum), 2 (approximate to0.86 mum) and 4 (approximate to 0.55 mum) of the Moderate-Resolution Imaging Spectroradiometer (MODIS Terra) has been evaluated by comparison of the top-of-atmosphere (TOA) albedos measured in the three bands over a six-day period with a three-year record of TOA albedos measured in the 0.56, 0.66 and 0.86 mum channels of the Along-Track Scanning Radiometer-2 (ATSR-2). The albedo measurements were made over two radiometrically stable sites located in the Libyan desert (22degrees0’N, 28degrees30’E), Sudan, and in the Sonoran desert (32degrees0’N, 114degrees6’W), Mexico. MODIS Terra albedos are within +/-2.5 per cent of those measured in the corresponding channels of ATSR-2. Analysis of the measurements, and of model-derived albedos in the three channels (bands) of the two instruments, indicates that the MODIS Terra on board calibrator for bands 1, 2 and 4 is functioning as expected, and that either of the two instruments can be used to monitor the in-orbit performance of the other.