Abstract: The present invention provides a tracking sensor and system to maintain the alignment of an optical communication beam between two terminals. A four-quadrant InGaAs photodetector receives the optical beam. Each quadrant of the photodetector transmits the signal to channel circuitry. The channel circuitry synchronously demodulated the signal to calculate received power. The received power for each signal is supplied to an up/down adder, a left/right adder and a total power received adder which provide the relative powers received in the upper half with respect to the lower half and in the left half with respect to the right half as well as the total power received. The fine track mechanism of the receiving terminal is adjusted to equalize the received power for each half. When each half is receiving equal power, the optical beam is centered. The photodetector, channel circuitry, and adders are contained in a single, hermetically sealed package with an optical window through which the optical signal passes.

Abstract: The present invention provides an acquisition sensor and system to align the communication lasers of two satellite communication terminals so that the satellites acquire one another to allow laser communication. The communications lasers of both satellites are scanned over their respective pointing uncertainty regions. Each satellite's acquisition sensor detects the presence of the scanned beam of the other satellite and provides positional resolution of the other satellite. Each satellite than adjusts its scanning to conform with the new positional data. of the other satellite. The acquisition sensor is a quadrant InGaAs photo-detector and accompanying monolithic acquisition processing circuitry sealed in a hermetic package with an optical window. Each quadrant of the sensor is responsive to the beam of the other satellite, thus providing positional resolution of the other satellite to the space of a single quadrant.