ASTER DEM performance

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument onboard the National Aeronautics and Space Administration's Terra spacecraft has an along-track stereoscopic capability using its a near-infrared spectral band to acquire the stereo data. ASTER has two telescopes, one for nadir-viewing and another for backward-viewing, with a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal plane. Parameters such as the line-of-sight vectors and the pointing axis were adjusted during the initial operation period to generate Level-1 data products with a high-quality stereo system performance. The evaluation of the digital elevation model (DEM) data was carried out both by Japanese and U.S. science teams separately using different DEM generation software and reference databases. The vertical accuracy of the DEM data generated from the Level-1A data is 20 m with 95% confidence without ground control point (GCP) correction for individual scenes. Geolocation accuracy that is important for the DEM datasets is better than 50 m. This appears to be limited by the spacecraft position accuracy. In addition, a slight increase in accuracy is observed by using GCPs to generate the stereo data.     

Design and preflight performance of ASTER instrument protoflightmodel

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imager with high spatial, spectral, and radiometric resolution, built to fly on the EOS-AM1 spacecraft along with four other instruments, which will be launched in 1998. The ASTER instrument covers a wide spectral region, from visible to thermal infrared with 14 spectral bands. To meet the wide spectral coverage, optical sensing units of ASTER are separated into three subsystems: visible and near-infrared (VNIR) subsystem, shortwave infrared (SWIR) subsystem, and thermal infrared (TIR) subsystem. ASTER also has an along-track stereoscopic viewing capability using one of the near-infrared bands. To acquire the stereo data, the VNIR subsystem has two telescopes, one for nadir and another for backward viewing. Several new technologies are adopted as design challenges to realize high performance. Excellent observational performances are obtained by a pushbroom VNIR radiometer with a high spatial resolution of 15 m, a pushbroom SWIR radiometer with high spectral resolution, and a whiskbroom-type TIR radiometer with high spatial, spectral, and radiometric resolutions. The preflight performance is evaluated through a protoflight model (PFM)     

ASTER Level-1 data processing algorithm

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imager with high spatial, spectral, and radiometric performance built for the EOS-AM1 polar orbiting spacecraft. ASTER covers a wide spectral region from visible to thermal infrared with 14 spectral bands. To meet this wide spectral coverage, ASTER has three optical-sensing subsystems: visible and near-infrared (VNIR), shortwave infrared (SWIR), and thermal infrared (TIR). In addition, the VNIR subsystem has two telescopes (nadir and backward telescopes) for stereo data acquisition. This ASTER instrument configuration with multitelescopes requires highly refined ground processing for the generation of Level-1 data products that are radiometrically calibrated and geometrically corrected. The algorithm developed for the ASTER Level-1 data processing is described