Neue Verarbeitungsverfahren von Along-Track Interferometrie Daten eines Radars mit synthetischer Apertur

The German remote sensing project EURoPAK-B is aimed at the development and the demonstration of a special remote sensing system for the measurement of ocean surface currents and the monitoring of underwater bottom topography in coastal waters on the basis of airborne along- track interferometric (ATI) synthetic aperture radar. In contrast to across-track interferometry ATI is directly sensitive to motions of the scatterers which have a radial velocity component. The ATI phase being directly proportional to the interferometric velocity contains not only contributions resulting from the effective ocean surface currents but also from effects like e. g. orbital motions of longer waves. Thus the actual surface ocean currents differ from the measured interferometric velocities. The processed ATI phase is the starting point for the determination of interferometric velocities and has to be handled accurately. Therefore some concepts concerning a very proper processing of ATI data have to be developed. This includes the correction of phase contributions resulting from the wave guide length at different channel frequencies. Another undesirable contribution to the phase results from the existing across-track component which depends on the squint angle during data acquisition. To minimize that effect the exact positions of the phase centres of both antennas have to be determined in a theoretical way. Also some other effects on the ATI data like the azimuthal displacement of moving targets have to be taken into account for a correct geolocation of the ATI data. This work gives also reasons why the ATI phase has to be unwrapped although the phase resulting from the ocean currents should be within the order of -π and +π. It will also been shown how phase unwrapping errors of the ATI phase can be removed. In this work these concepts for accurately processing ATI data are discussed and results are shown. Supplementary it points out the proposed remote sensing technique for accurate measurements of both ocean surface currents and underwater bottom topography in coastal waters generated by the University of Hamburg.