ASTER

ASTER ( Advanced Spaceborne Thermal Emission and Reflectance Radiometer) is an imaging instrument onboard Terra - the first Earth Observing System (EOS) satellite. Terra was launched on December 18, 1999 from the Vandenberg Air Force Base in California and flies in a sun-synchronous polar orbit, crossing the equator in the morning at 10:30 am. ASTER is one of five state-of-the-art instrument sensor systems onboard Terra with a unique combination of wide spectral coverage and medium spatial resolution in the visible, near-infrared through shortwave infrared to the thermal infrared regions. ASTER data contributes to a wide array of global change-related applications including vegetation and ecosystem dynamics, hazard monitoring, geology and soils, land surface climatology, hydrology and land cover change.
ASTER consists of three different subsystems; the Visible and Near Infrared (VNIR), the Shortwave Infrared (SWIR) and the Thermal Infrared (TIR). The VNIR subsystem consists of two independent telescope assemblies. One is vertical looking and has three detector arrays collecting data in the visible green, visible red and near infrared wavelengths, while a backward looking telescope has one detector array in the same spectral band as the near infrared of the vertical array. The two near infrared (3N and 3B) generating an along-track stereo image pair with a base-to-height ratio of 0.6 and an intersection angle of 27.7degs which can be used to generate digital elevation models.