Satellite Wide Area Multilateration Solution, Applications, and Benefits

Wide Area Multilateration (WAM) surveillance systems provide a robust and effective means of surveilling aircraft; these systems can operate both actively (interrogating aircraft for necessary messages) or passively, using available messages of opportunity, to determine aircraft positions. WAM systems do not require any information from aircraft transmissions other than a form of identification to group multiple received messages from the same transmission together, resulting in a surveillance solution that is independent of any onboard aircraft systems, such as Global Navigation Satellite System (GNSS). The methods and calculations required to perform multilateration are standardized in the aviation industry and have been implemented by many systems around the world. What is not common for WAM systems is the use of extremely fast mobile and/or very distant receivers, such as satellites. Generally, most WAM systems, especially Air Traffic Control (ATC) grade systems, require highly accurate position and timing information for the receivers, typically done via site surveys and highly accurate clocks for the ground stations. When the receiver is mobile, this makes the receiver location uncertainty a problem for accurately solving for the transmitter's location. Aireon, working with Iridium, has access to Precision Timing and Position (PTP) data which enables the required accuracies on the receiving satellites to perform Time Difference of Arrival (TDOA) calculations, the staple of a WAM system. Using the Iridium constellation's unique geometry, there are many areas of the world covered by the three or more requisite receivers to perform two-dimensional multilateration. One of these areas is the North Atlantic Tracks, which regularly has three or more Iridium satellites providing coverage. Building on the work done for a paper presented at DASC 2023, this paper provides analysis of the performance of a Satellite Wide Area Multilateration solution operating on thousands of aircraft as a proof-of-concept for widespread applications. Additionally, using this solution, this paper will also investigate the robustness of this style of surveillance against GNSS jamming and spoofing events which have become more common and affect more airspaces every day.