期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2002
卷号：XXXIV Part 1
出版社：Copernicus Publications
摘要：SPOT5 Location model calibration addresses five main issues. The first issue is to get best relative and absolute location performances. It consists of relative orientation calibration for HRG, HRS and stellar location unit reference frames. Such a calibration started in-house, using theodolites; it ends in-flight using GCPs. The second issue is to get a model of THR pairs relative shifts good enough to deliver the best 2.5m sampled image. The first ever, true HRG images have been acquired during satellite design, a few months before launch. Such images contributed to THR processing validation and allowed ground calibration of THR det ection lines relative shifts, way before launch. In-flight measures confirmed that such ground measures are reliable. Third issue is to turn HRS stereo pairs parallax in a precise enough altitude estimate. That means that HRS location models have to include an accurate model of objectives distortion. A fourth issue consists of HRG's steering mirror mechanism calibration, in order to get the same location performance, whatever the HRG mirror viewing angle is. Final issue deals with optimisation of time delay between two HRG off nadir images acquisition. Such time delay depends on mirror damping speed. For a given viewing angle, called "Autotest", one can acquire HRG images of a designed pattern located in the focal plane. A straightforward processing of this kind of images indicates if the mirror command can be improved. This new calibration process is available in flight as well as on ground. After the two months commissioning phase, objectives are met: images location models are accurate enough to meet all requirements. Absolute location performances provided by the stellar unit are such that new phenomena, never seen on initial SPOT satellites, appear. Initial results show performances trends that we should be able to model, once confirmed through further images acquisition. We specially think about orbital and/or seasonal effects. Work is still carried on
