Performance of the CARABAS-II VHF-band synthetic aperture radar

CARABAS-II is an airborne SAR operating in the 20-90 MHz band. The low operating frequency enables detection of concealed objects in dense forests as well as mapping of forest stem volume. A number of calibration experiments have recently been conducted to evaluate system performance. In this paper, we report on some of the results from the analysis. Spatial resolution, measured using 5-m trihedrals, is typically 2.5 m in both slant range and azimuth. The right-left ambiguity ratio, measured using 5-m trihedrals on both sides of the flight track, is about 10 dB for a single antenna element on receive. The noise level varies in the images and includes both multiplicative (integrated sidelobe ratio, right-left ambiguity ratio) and additive (radio-frequency interference, receiver noise) terms. Analysis of images from a recent campaign in northern Sweden shows that the additive noise term is less than -20 dB (noise-equivalent β°) for slant ranges less than 14 km