  Maintaining optical alignment between stations of a free-space optical link
requires a persistent beam tracking operation. This is achieved using a
position-sensitive photodetector at each station which measures the azimuth and
elevation of tracking error. A pointing assembly adjusts the heading of
transceivers according to measurement of the tracking error. The measurement at
each receiver also depends on the pointing error of the opposite transmitter,
therefore a cooperative beam tracking system can be regarded as two dynamically
coupled subsystems. We developed a stochastic model for a cooperative beam
tracking system to get insight into solution of an associated optimal control
problem with goal of maximizing the flow of optical power between the stations.
