ABSTRACT

Synthetic Aperture Radar (SAR) has become a powerful tool for remotely observing the earth. Airborne SAR systems allow imaging medium-to-large areas with ad hoc missions whereas spaceborne SAR systems are mainly designed for continuous monitoring of vast areas at a global scale, although the monitoring of a selected area may occur only at a given prescheduled time (revisiting time). Anyway, recent spaceborne systems, such as Cosmo Skymed (CSK), have reduced the revisiting time by introducing the concept of SAR constellation and by making each satellite as

14.1 Introduction .......................................................................................................................... 275 14.2 Spotlight SAR Algorithms ................................................................................................... 277

14.2.1 ω-k Algorithm .......................................................................................................... 278 14.2.2 Polar Format Algorithm ........................................................................................... 279 14.2.3 Chirp Scaling Algorithm ..........................................................................................280

14.3 SAR Inversion Mapping ....................................................................................................... 282 14.3.1 ω-k Inversion ............................................................................................................ 282 14.3.2 Polar Format Inversion ............................................................................................. 283 14.3.3 Chirp Scaling Inversion ............................................................................................ 283 14.3.4 Fourier Inversion .......................................................................................................284

14.4 ISAR Processing ...................................................................................................................285 14.4.1 Autofocus ..................................................................................................................286 14.4.2 Image Formation .......................................................................................................287 14.4.3 Time-Windowing ......................................................................................................288 14.4.4 Cross-Range Scaling .................................................................................................288

14.5 Experimental Results ............................................................................................................ 289 14.5.1 CSK Product Description ......................................................................................... 289 14.5.2 CSK SAR Images .....................................................................................................290 14.5.3 Refocussing Results ..................................................................................................290