ASTER PREFLIGHT AND INFLIGHT CALIBRATION AND THE VALIDATION OF LEVEL-2 PRODUCTS

This paper describes the preflight and inflight calibration approaches used for the Advanced Spaceborne Thermal Emission and Reflection Radi ometer (ASTER), The system is a multispectral, high-spatial resolution sensor on the Earth Observing System's (EOS)-AM1 platform, Preflight calibration of ASTER uses well-characterized sources to provide calibr ation and preflight round-robin exercises to understand biases between the calibration sources of ASTER and other EOS sensors. These round-r obins rely on well-characterized, ultra-stable radiometers, An experim ent held in Yokohama, Japan, showed that the output from the source us ed for the visible and near-infrared (VNIR) subsystem of ASTER may be underestimated by 1.5%, but this is still within the 4% specification for the absolute, radiometric calibration of these bands. Inflight cal ibration will rely on vicarious techniques and onboard blackbodies and lamps. Vicarious techniques include ground-reference methods using de sert and water sites. A recent joint field campaign gives confidence t hat these methods currently provide absolute calibration to better tha n 5%, and indications are that uncertainties less than the required 4% should be achievable at launch. The EOS-AM1 platform will also provid e a spacecraft maneuver that will allow ASTER to see the moon, allowin g further characterization of the sensor. A method for combining the r esults of these independent calibration results is presented. The pape r also describes the plans for validating the Level 2 data products fr om ASTER, These plans rely heavily upon field campaigns using methods similar to those used for the ground-reference, vicarious calibration methods.