Spaceborne synthetic aperture radar (SAR) systems are used to measure geo- and biophysical parameters of the Earth's surface, e.g. for agriculture, forestry and land subsidence investigations. Upcoming SAR sensors such as the Japanese Phased Array L-band Synthetic Aperture Radar (PALSAR) onboard the Advanced Land Observing Satellite (ALOS) exemplify a trend towards lower frequencies and higher range chirp bandwidth in order to obtain additional information with higher geometric resolution. However, the use of large bandwidths causes signal degradation within a dispersive medium such as the ionosphere. Under high solar activity conditions at L-band frequencies, ionosphere-induced path delays and Faraday rotation become significant for SAR applications. Due to ionospheric effects, blind use of a generic matched filter causes inaccuracy when correlating the transmitted with the received signal. Maximum correlation occurs where the length of the matched filter, based on a synthetic chirp model of the transmitted signal, is adjusted to correspond to that of the received signal. By searching for the proper adjustment necessary to reach this maximum, the change in length can be estimated and used to derive variations in the total electron content (TEC) and degree of Faraday rotation within the ionosphere from all range lines in a SAR image.

Date Published: 1 November 2005
PDF: 9 pages
Proc. SPIE 5979, Remote Sensing of Clouds and the Atmosphere X, 59790U (1 November 2005); doi: 10.1117/12.627618

Published in SPIE Proceedings Vol. 5979:
Remote Sensing of Clouds and the Atmosphere X
Klaus Schäfer; Adolfo T. Comerón; James R. Slusser; Richard H. Picard; Michel R. Carleer; Nicolaos Sifakis, Editor(s)