The Hydrographic Doppler Sonar System (HDSS) on the R/V Revelle provides profiles of absolute ocean current and acoustic scattering strength in support of scientific operations. The HDSS consists of a 50 kHz Doppler sonar which returns data in a depth range between 20 m and 700-1100 m (depending on conditions), and a 140 kHz Doppler sonar which returns data in a depth range between 20 m and 150-350 m (depending on conditions). The system was created to provide measurements with higher depth resolution than is available from commercial Doppler sonars. Both the acoustic pulse length and the angular width of an acoustic beam affect depth resolution. HDSS uses large transducers to get narrower beams and greater power to get greater range without sacrificing vertical resolution.
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