Beaconless satellite laser acquisition - modeling and feasability

Optical satellite links require microradian pointing accuracies for acceptable received power levels with microradian beam divergences. Errors in attitude estimation, ephemeris accuracy and platform to boresight alignment are typically on the order of several milliradians, necessitating an acquisition process to locate the actual position of the satellite in space. This process involves scanning a laser (the search beacon) over an error cone until detection occurs onboard the satellite and a two-way link can be established. Current systems use a spoiled large divergence beacon laser for the acquisition and link initialization process, and then switch to a diffraction limited communications laser for fine tracking and data transfer. If the communications laser can be used for the acquisition process instead, the extra complexity of the beacon laser can be eliminated, resulting in considerable savings. A detailed model of the acquisition process is developed and used to show that a diffraction-limited beam can be used for acquisition under some circumstances involving benign vibration environments. The same methodology is used to determine an optimal beam divergence in other cases.