Abstract: A deep water explosive echo ranging system capable of detecting high perfance submarines by using favorable acoustic paths available at deep depths. An umbrella hydrophone array is deployed from a sonobuoy to deep depths; an electrical subsystem transmits data from the hydrophone array to a transmitter housed in a surface float unit; a multichannel receiver and signal processing and display apparatus in an aircraft receives and processes radio data signals sent from sonobuoy transmitters; and an explosive underwater charge package is remotely triggered by a command generator in the aircraft.