Abstract
Non-cooperative tracking of shipping from space has traditionally been the preserve of state actors. Recent progress in nanosat and SDR technology raises the possibility of conducting such surveillance from low-cost space platforms. While ships may switch off beacons in order to obscure their location, they cannot proceed safely without their navigation radar systems being operational. Radar emissions may be recorded to achieve geolocation. As the radar antenna is mechanically rotated, a periodic power peak is observed by a fixed receiver. A receiver in LEO will record differing interception times according to its motion and that of the emitter platform. A least squares estimator is used to compare possible emitter locations with the collected data in order to arrive at the most probable geolocation. The highly constrained geometry of the system reduces the search to a 1-dimensional one which significantly reduces the processing power required for a fast answer. It is suggested that power reduction resulting from a new algorithm, coupled with advances in nanosat and SDR technology enables a low-cost demonstrator mission. Additionally, using only one satellite removes the requirement for high-speed data links, further reducing weight and power needs. Accuracies of better than 20km have been recorded in simulations.