Fusion of range-only measurements from multistatic configurations for air collision warning

A requisite for unmanned aircraft systems (UAS) to operate within a controlled airspace is a capability to sense and avoid collisions with non-cooperative aircraft. Ground-based transmitters and UAS-mounted receivers are preferred due to the limitations on the size, weight and power of UAS. This paper assumes a constant velocity motion of an intruder (target) aircraft and presents a method to estimate the state (motion parameters - position and velocity) of the target so as to predict a possible collision point. Bistatic range and Doppler are assumed the only measurements available, with the employment of low-cost omni-directional antennas. Several configurations are investigated from a parameter observability point of view. The target motion parameter is shown not to be observable in a bistatic configuration and a change of course of the receiver merely yields marginal observability. In a multistatic configuration, one has marginal observability using two transmitters but good observability with three transmitters. Simulation results show that the position estimate of the possible collision point is statistically efficient in the 3-transmitter multistatic configuration.