94-GHz Tarsier radar measurements of wind waves and small targets

Tarsier is QinetiQ´s 94-GHz frequency-modulated continuous-wave radar and is installed at several airports worldwide for detecting Foreign Object Debris on runways. The radar is coherent and has a range resolution of 0.3 metres. The sensitivity of the radar that allows it to detect an object the size of a metal bolt at a range of 2 km on land means that in the maritime environment it may detect difficult maritime targets such as swimmers, jetskis, windsurfers, canoes and disturbances of the water surface. This paper describes trials of the Tarsier radar at Cheddar reservoir near Axbridge in Somerset. Noncoherent and coherent radar measurements of wind waves were recorded to characterize the background clutter. Targets of opportunity included buoys, wildfowl, windsurfers, rowing boats and a model yacht. A standard 9.4-GHz marine navigation radar was operated at the same time and location to allow a direct comparison of clutter and target signatures at the two different radio frequencies. Results are presented for 94-GHz clutter histograms and Doppler spectra as a function of radar look direction and wind speed. Target signal-to-clutter ratios are discussed for 94 GHz and for 9.4 GHz. It is concluded that Tarsier has the potential to detect short-range maritime threats at this relatively unexplored radio frequency.