Remote sensing of sea state by radar

Abstract

In recent years several radar techniques have evolved which allow the remote measurement of certain parameters important in the description of sea state. At MF and HF, monostatic and bistatic configurations employing satellites, ships, islands, and/or land based stations can measure the ocean waveheight spectrum with several frequencies via first-order Bragg scatter. At high HF and VHF, the ocean waveheight spectrum can be estimated at a single carrier frequency via secord-order mechanisms; this technique is especially suited to remote sensing via long distance ionospheric propagation. At UHF, it is possible to measure the slope spectrum of the longer ocean waves via cross-correlation of simultaneous Bragg-effect returns at two frequencies. The short-pulse microwave satellite altimeter permits a direct measurement of the significant waveheight of the sea at the suborbital point via the specular point mechanism. Such techniques will be important both for detailed oceanographic study of ocean wave characteristics and for routine monitoring of sea state for maritime/meteorological purposes.