Introduction

Side-looking imaging radars provide a powerful way to retrieve ice and ocean surface backscatter properties at a high resolution and for nearly all weather conditions. Given that many geophysical processes modulate the Bragg scattering waves, the returns from these radars can be formed into images that display a wide variety of surface phenomena. Other advantages are that, depending on the processing, the resolution can be of order meters, and at the frequencies used by these radars, the atmosphere is transparent except for heavy rain.

There are two kinds of satellite imaging radars: synthetic aperture radar (SAR) and the real-aperture side-looking radar (SLR). The SLR is a range-binned instrument with a surface resolution of about 1 km; the SAR is a more complicated instrument with resolutions as fine as 3 m. Because the radar pulses illuminate the surface, the instruments provide day and night coverage. SAR is the principal radar imager used in oceanographic research, where SARs have been flown by the United States, Canada, ESA, Germany, Italy, Japan and Russia. Because the SLR operates similarly to SAR in the cross-track direction and was used by Russia and Ukraine for sea ice monitoring through the year 2000, this chapter covers both instruments but emphasizes SAR.