ABSTRACT
Excluding dedicated atmospheric, meteorological, and defense satellites, there are more than 30 sensors, in space designed for terrestrial imaging. These sensors are a variety of national and international efforts representing more than 12 countries. They range in spatial resolution from 0.6 to 1000 m with spectral resolution from multispectral to hyperspectral spanning the wavelength regions from visible, near-infrared, thermal infrared, and radar. Swath widths and repeat visits also span a wide range of values all leading to an opportunity to study Earth processes on a global scale. Critical to this approach is the ability to compare data between scales and sensors, and a key part of this is absolute radiometric calibration. Absolute radiometric calibration allows data from individual sensors to be compared directly so long as traceability to known
standards is maintained and estimates of absolute accuracy are themselves accurate.
