Abstract
ROSAS (Robotic Station for Atmosphere and Surface) has been used since 1997 in the site of LaCrau, in South East of France, to perform ground truth campaigns. The principle of these campaigns is to characterize the optical properties of the atmosphere through measurements of the solar extinction, sky radiance and upwelling radiance of the ground, simultaneously to the satellite overpass. The data are automatically processed, in order to calibrate the photometer and estimate the bidirectional reflectance distribution function of the site. This allows to simulate the top of atmosphere radiance in the geometric conditions of any satellite over-passing the site. The instrument, calibration principle and measurement protocol will be presented first. Then, after a description of the operational software used to collect and process the data, the first PLEIADES calibration results will be discussed, and compared to the results of other calibration methods. Taking advantage of PLEIADES tremendous agility, a single over-pass can contain up to 24 different satellite viewing angles over the calibration site, allowing to cross-validate the estimation of the bidirectional reflectance distribution of the site, thus improving the computation of the TOA radiance, and the accuracy of the calibration results.
The Contribution of ROSAS Automated Photometric Station to Vicarious Calibration of PLEIADES PHR1A Satellite
ROSAS (Robotic Station for Atmosphere and Surface) has been used since 1997 in the site of LaCrau, in South East of France, to perform ground truth campaigns. The principle of these campaigns is to characterize the optical properties of the atmosphere through measurements of the solar extinction, sky radiance and upwelling radiance of the ground, simultaneously to the satellite overpass. The data are automatically processed, in order to calibrate the photometer and estimate the bidirectional reflectance distribution function of the site. This allows to simulate the top of atmosphere radiance in the geometric conditions of any satellite over-passing the site. The instrument, calibration principle and measurement protocol will be presented first. Then, after a description of the operational software used to collect and process the data, the first PLEIADES calibration results will be discussed, and compared to the results of other calibration methods. Taking advantage of PLEIADES tremendous agility, a single over-pass can contain up to 24 different satellite viewing angles over the calibration site, allowing to cross-validate the estimation of the bidirectional reflectance distribution of the site, thus improving the computation of the TOA radiance, and the accuracy of the calibration results.