A proposal for the development of a repository for in-flight calibration of optical sensors over terrestrial targets.

Calibration of optical sensors onboard earth observation satellites has been a major issue for several years. A collection of techniques has been developed involving modelisation, surface or airplane based measurements of surface and atmosphere characteristics. The present study has the following objectives: conceive and develop a repository for all available data sets related to optical sensor calibration, including selection of commonly used sites, characteristics of the surface, climatology of the atmosphere, ground-and air-based measurements as well as results of calibration of various sensors over these sites. The main goal is to unify the use of these sites to make inter comparison of results easier and the calibration of forthcoming sensors more accurate at little extra expenses. Conception of the database and its environment will identify the type of data to gather, the format to use, the updating frequency, as well as the theoretical background necessary to the use of these data. For instance, information will be given about spectral behavior of the surface or about how to make measurements at various resolution easy to compare.