Satellite-based ADS-B (also space-based ADS-B) is the reception of Automatic Dependent Surveillance–Broadcast (ADS-B) signals transmitted by aircraft, by receivers carried on satellites in low Earth orbit (LEO) rather than by ground stations.Although the signals were designed primarily for reception by other aircraft and terrestrial stations, 1090 MHz Extended Squitter transmissions can also be detected from orbit by suitably designed satellite receivers and relayed to air navigation service providers (ANSPs). Space-based reception extends ADS-B-based air traffic surveillance from the roughly 30% of the Earth's surface covered by terrestrial radar and ground ADS-B receivers to the entire globe, including the oceanic, polar and remote-continental airspace where controllers previously depended on procedural separation and pilot-reported position updates. The first space-based reception of ADS-B signals was demonstrated in 2013 by the European Space Agency's Proba-V satellite, and was followed by CubeSat experiments developed by GomSpace and Aalborg University. The first operational service was launched in March 2019 by Aireon, a joint venture between Iridium Communications and several ANSPs, after Harris-built ADS-B receiver payloads were hosted on all 75 second-generation Iridium NEXT satellites. NATS and Nav Canada activated the service over the North Atlantic on 27 March 2019, and used the new surveillance to implement reduced aircraft separation minima under the ICAO Advanced Surveillance-Enhanced Procedural Separation (ASEPS) standards. The first space-based reception of ADS-B signals was demonstrated in 2013 by the European Space Agency's Proba-V satellite, and was followed by CubeSat experiments developed by GomSpace and Aalborg University. The first operational service was launched in March 2019 by Aireon, a joint venture between Iridium Communications and several ANSPs, after Harris-built ADS-B receiver payloads were hosted on all 75 second-generation Iridium NEXT satellites. NATS and Nav Canada activated the service over the North Atlantic on 27 March 2019, and used the new surveillance to implement reduced aircraft separation minima under the ICAO Advanced Surveillance-Enhanced Procedural Separation (ASEPS) standards.
Background ADS-B is a cooperative-surveillance technology in which an aircraft determines its position via satellite navigation and broadcasts it, together with identity and velocity information, on 1090 MHz (1090ES) or, for general aviation in the United States, on 978 MHz (UAT). Ground-based ADS-B receivers and secondary surveillance radar cover only the populated continents and adjacent coastal waters; over the open ocean, the Arctic and large parts of Africa, Australia and the Pacific, controllers have traditionally relied on position reports transmitted by pilots over HF voice or via FANS-1/A data link every 10 to 14 minutes, with procedural separation minima of 40 nmi longitudinally and up to 60 nmi laterally between aircraft.
Reception characteristics Receiving ADS-B signals from orbit presents different radio-frequency conditions from terrestrial reception. Tests with Proba-V found that the greater distance between an aircraft and a satellite results in substantially weaker signals, which may need to be detected close to the receiver's noise level. Reception is also affected by the radiation patterns of both the aircraft and satellite antennas, and by garbling, in which simultaneous ADS-B transmissions overlap at the receiver and cannot be decoded. Aircraft surveillance antennas have a toroidal vertical radiation pattern, producing an area of reduced signal strength approximately directly above an aircraft. During the Proba-V experiment this produced a measurable reduction in reception near the satellite's nadir, with the effect varying according to aircraft antenna placement and fuselage geometry. DLR concluded that an operational system could mitigate antenna-pattern effects and signal congestion by using multi-channel receivers with slant-pointing spot-beam antennas.
Early experiments
Proba-V (2013) The first ADS-B receiver to operate in orbit flew on Proba-V, a European Space Agency technology-demonstration mission launched on 7 May 2013 from the Guiana Space Centre on a Vega launch vehicle. The receiver was developed by the German Aerospace Center (DLR) with ground processing support from Luxembourg-based operator SES. By mid-2015, Proba-V had detected more than 25 million ADS-B position messages from aircraft worldwide, which ESA described as a "technical world first" in the satellite-based monitoring of air traffic.
GOMX-1 and GOMX-3 GomSpace of Aalborg, Denmark, in collaboration with Aalborg University and DSE Airport Solutions, flew the 2U CubeSat GOMX-1 (launched 21 November 2013), which carried a software-defined radio payload to receive 1090ES signals over oceanic regions. The follow-on GOMX-3, a 3U CubeSat developed for ESA, was deployed from the International Space Station in October 2015 after launch on the HTV-5 cargo mission and carried an improved ADS-B receiver alongside an L-band software-defined radio.
Aireon and Iridium NEXT
Joint venture and financing Aireon LLC was formed in 2011 by Iridium Communications together with a group of ANSP partners — Nav Canada, NATS, ENAV, Naviair and the Irish Aviation Authority, later joined by Isavia — to deploy and operate a global space-based ADS-B service. The formal joint-venture agreement between Iridium and Nav Canada was completed on 19 November 2012; Nav Canada committed up to $150 million over five tranches to acquire a 51% stake in the venture.
Receiver design The Aireon payload is a 1090 MHz Extended Squitter receiver built by Harris Corporation (later part of L3Harris Technologies). Harris announced completion of all 81 ADS-B payloads on 1 June 2016 ahead of schedule; the units were destined for the 66 operational satellites, 9 on-orbit spares and 6 ground spares of the Iridium NEXT constellation. Decoded messages are routed through Iridium's Ka-band cross-links and ground gateways to Aireon's distribution network, which delivers position reports to ANSPs and to commercial users via FlightAware.
Deployment
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