A technical assessment of ADS-B and multilateration technology in the Gulf of Mexico

Two aircraft surveillance technologies, multilateration and ADS-B, have emerged during the past few years and now appear to be possible alternatives to traditional primary and secondary radar systems. Multilateration has been tested extensively for airport surface applications - e.g., test in Atlanta (1996) and Federal Aviation Administration (FAA) tests at Dallas-Forth Worth (1998-1999). The FAA plans to deploy multilateration/ADS-B systems as part of the airport surface detection equipment-X (ASDE-X) system now scheduled for installation at 25 non-ASDE-3 equipped airports. There is, however, limited experience with multilateration for tracking of airborne aircraft. HITS, based on commercially available equipment, forms the ground segment of a dual-technology multilateration and ADS-B aircraft tracking system. Multiateration utilizes signals from air traffic control radar beacon system (ATCRBS) (Modes A and C) and Mode S transponders, and requires no changes in current aircraft equipage. HITS also operates with signals from ADS-B Mode S extended squitter transponders now being considered for operation in the National Airspace Systems (NAS). To assess the performance of HITS, technical requirements were derived from ATCBI-6 SSR to compare the technical performance of HITS against FAA secondary radar. The evaluation criteria include coverage volume, probability of detection, positional accuracy, code performance, and target resolution. These criteria were derived to assist the FAA in assessing the technical feasibility and possibly developing certification criteria for these two potential non-radar surveillance alternatives. The results from this test and evaluation will provide important data to the FAA as it attempts to determine the feasibility of implementing multilateration and ADS-B in terminal and en route environments. This paper details the technical results and the HITS system performance.