Abstract: An apparatus for sensing mis-alignment between an aircraft inertial reference frame and a reference frame of an attached sensor is disclosed. The apparatus includes a first laser mounted on the sensor and in the center of and normal to a first measuring surface; and, a second laser also mounted on the sensor perpendicular to the first laser and in the center of and normal to a second measuring surface. A first reflector is mounted to and aligned with the inertial reference frame of the aircraft and is disposed for reflecting a beam of light from the first laser, whereby misalignment in roll and yaw between the sensor and the aircraft is reflected on the first measuring surface.

Abstract: An apparatus for sensing mis-alignment between an aircraft inertial reference frame and a reference frame of an attached sensor is disclosed. The apparatus includes a first laser mounted on the sensor and in the center of and normal to a first measuring surface; and, a second laser also mounted on the sensor perpendicular to the first laser and in the center of and normal to a second measuring surface. A first reflector is mounted to and aligned with the inertial reference frame of the aircraft and is disposed for reflecting a beam of light from the first laser, whereby misalignment in roll and yaw between the sensor and the aircraft is reflected on the first measuring surface.

Abstract: In a time continuous transmit active sonar system the frequency of the transmitted waveform is interrupted at predetermined intervals so that a frequency discontinuity in the transmitted waveform occurs at each interruption. The starting and ending frequencies at the beginning and end of the interruptions provide indications for properly resolving the range/Doppler ambiguity that is inherent in prior continuous transmit sonar systems. The transmitted signal may be frequency modulated. Further, the frequency of the transmitted waveform may be rapidly changed and/or multiple frequency waveforms may be transmitted within the same time interval. An existing passive sonar detection system may be modified to include an active continuous transmit sonar system whose echo returns may be processed by the passive system, thereby achieving benefits over conventional active pulsed sonar systems.