A HELICOPTER-BORNE 8-CHANNEL RANGING SCATTEROMETER FOR REMOTE-SENSING.1. SYSTEM DESCRIPTION

A helicopter-borne dual-frequency FM-CW scatterometer (HUTSCAT, Helsin ki University of Technology SCATterometer) is described. The HUTSCAT m easures the backscattering properties of a target with a range resolut ion of 65 cm. The real-time ranging capability is obtained by performi ng the Fast Fourier Transform (FFT) to the received time-domain signal . The measurement is made simultaneously at eight channels (VV, HH, HV , and VH modes of polarization at 5.4 GHz and 9.8 GHz). The scatterome ter measures the radar return spectrum for eight channels in 16.6 ms w hich corresponds to an along-track distance of 0.33 m for the helicopt er speed of 20 m/s. The radar system has been designed for remote sens ing of forests, sea ice, and snow. The most potential application is t he estimation of forest stand characteristics, to be discussed in Part II of this paper.