Quasi-automatic Geometric Correction and Related Geometric Issues in the Exploitation of Chris/proba Data

The multiangular and off-track pointing capabilities of CHRIS/PROBA introduce a strong distortion on the geometry on the resulting images. In order to make full scientific use of the data some information about the geometry of acquisition is needed. In particular, the viewing azimuth and zenith angles must be known, and the images must be geometrically corrected to make possible multi-angular and multitemporal studies. CHRIS/PROBA images are distributed with ancillary data related to its acquisition. The angles provided with the images, Minimum Zenith Angle (MZA) and Fly-by Zenith Angle (FZA), accurately determine the satellitetarget geometry, but they are not the ones needed for atmospheric / angular corrections, and the information provided with the data is not enough to derive the required geometric information. There is an urgent need of precise methods to obtain the CHRIS/PROBA data in a practical format. That means precise Azimuth and Zenith Observation Angles for each image, and accurate geometric correction of the images. Also, the great volume of images provided demands, in order to be practical, that these methods should be automatic with a minimum intervention for quality checks in the processing.