Abstract: A satellite system for optical communications such as a multi-access laser transceiver system. Up to six low Earth orbiting satellites send satellite data to a geosynchronous satellite. The data is relayed to a ground station at the Earth's surface. The earth pointing geosynchronous satellite terminal has no gimbal but has a separate tracking mechanism for tracking each low Earth orbiting satellite. The tracking mechanism has a ring assembly rotatable about an axis coaxial with the axis of the field of view of the geosynchronous satellite and a pivotable arm mounted for pivotal movement on the ring assembly. An optical pickup mechanism at the end of each arm is positioned for optical communication with one of the orbiting satellites by rotation of the ring.

Abstract: An optical data communication system is provided whereby two orthogonal polarization states of a light beam carrier correspond to digital states. In such a system, automatic polarization compensation is provided by applying a dither modulating voltage to a cell exhibiting the electro-optic effect. The cell controls the relative phase of electric field components of an input light beam enabling the dither frequency component of the difference of the instantaneous powers in the two polarization states to be coherently detected. A signal derived from the coherent detection process is fed back to the cell via an integrator to form polarization bias compensating servo loop of Type I.

Abstract: A space-to-space or space-to-earth optical transmission link is simulated by positioning a linear optical modulator between an optical carrier source and a receiver for the carrier. The optical modulator is driven by an analog signal having random variations indicative of characteristics of the transmission link, as derived from an analog computer circuit. The analog computer circuit is responsive to a Gaussian random analog source. For certain types of links, the analog computer circuit is responsive to a pair of Gaussian analog signals which are derived by feeding a relatively wide band Gaussian analog source in parallel to a first low pass filter and to a heterodyne circuit that derives a beat frequency output that is passed through a second low pass filter having the same characteristics as the first low pass filter. For space-to-space transmission, transmitter pointing jitter is a dominant noise source and is simulated by deriving a beta statistical variation from the analog computer.