Lasercom crosslinking for satellite clusters

Clusters of small satellites which orbit in tight constellations and cooperatively perform radar, surveillance, data collection, and bent pipe communications, are being explored for potentially replacing the use of a single, larger, more complex satellite. Two basic requirements of these clusters are: communications must be available between any satellite pair, and range and position between any satellite pair must be continually monitored for computing the antenna configuration. While up/down links will most likely be RF, compact, lightweight, low power, lasercom direct detection optical packages can perform the crosslinking and position location operations. In this paper, a lasercom architecture is presented that utilizes pairs of relatively wide beam divergence optical beams to minimize pointing and tracking requirements and a point-to- point network topology. Data transfer is accomplished by the use of pulsed optical Code-Division-Multiplexing signaling formats, with address codes assigned to each satellite. A given satellite can establish a link with any other satellite by encoding data onto the proper address code. Some basic link budgets will be presented to scope the optical design in terms of power, data rate, and constellation size. Range and position can be obtained from the same lasercom architecture, using the address codes as ranging markers.