Abstract: A method is provided for remotely measuring index of refraction fluctuations. From a first location, an optical beam is focused at a focal plane located at a second location in a medium of interest. As a result, a beam of energy is backscattered towards the first location. At the first location, a size of the backscattered beam is determined where the size is indicative of strength of fluctuations in the medium's index of refraction.

Abstract: There is disclosed an exploder for an underwater weapon which periodically adiates an acoustic signal and activates the weapon only when the echo signal has the same phase as the radiated signal. Thus, echoes from any air-water interface are disregarded.

Abstract: Valid artificial targets are generated by means of an external attachment ilizing a calibration transducer affixed against a homing system transducer within the nose section of the Torpedo Mark 48 Mod 1. The calibration transducer comprises four elements bonded to a Rho-C rubber surface with each element located in separate quadrants. A plurality of phase shifters for nulling purposes are connected between the four elements. Phase shifted signal inputs then enable the calibration transducer elements to provide acoustic signals corresponding to predetermined target angles.