A highly reflective low cost backscattering target

A low cost biplanar reflector target has been developed and used in a system performance test of a near surface omnidirectional source and receiver. The target was constructed from sheets of closed cell plastic bubble sheeting. Theoretically, this material should have very high reflectance characteristics, and this was demonstrated by the experiment. The strongly reflecting target was located at the sea surface, and allowed the interpretation of data as the ship passed through a range of azimuthal angles. The higher than expected backscatter from the target was presumed to be due to the bubble sheeting behaving as a coherent reflector, like a thin layer of air, rather than an ensemble of individually resonating bubbles. This was verified by the data analysis. Lloyd's mirror effects were strong, because practically all of the return signals from the 10-ms continuous wave pulses were overlapping. The target strength (TS) of the reflector was strongly reduced at ranges over 100 m. The experiment shows that studies of the statistical distribution of fish school TS must consider the effects of Lloyd's mirror.