This parameter is useful in calibration and correction of other measurements made with remote sensing instruments at FED sites. It follows the sun automatically using a 4 quadrant detector. Spatial Resolution Spatial resolution is a function of the solar zenith angle and as such is not pertinent to measurements by a sunphotometer. Thus for 30 degrees, it is 5 km.
Meteorological parameters determine the effective spatial resolution.
The time of optical thickness data acquisition was in September, 1990. To measure the aerosol optical thickness using a multi-channel sunphotometer. This is part of the Correction and Calibration effort for FED, and will allow the estimation of the atmospheric effects on the transmitted and reflected radiation so that the appropriate correction schemes can be employed to infer reflectivity of the ground from aircraft radiometric data. The detector is a silicon photodiode detector which is kept at a constant tempera- ture. 4.4 Instrument Measurement Geometry.