Abstract
Automatic Dependent Surveillance-Broadcast (ADS-B) is an air traffic surveillance technology in which aircraft broadcast position, identification and status an average of 6.2 times per second on 1090 MHz. The Royal Military College of Canada has developed an ADS-B receiver that is scheduled to fly as a technology demonstrator on the Canadian Advanced Nanospace eXperiment-7 (CanX-7) nanosatellite. A signal propagation model was developed to determine the power level and number of signals that will be detected by CanX-7. Since the ADS-B messages are alternately transmitted from upper and lower antennas, both the direct and reflected signals were considered. A simulation using the model was run over the North Atlantic with aircraft data supplied by air traffic services and a satellite altitude of 800 km. Power at the receiver for reflected ADS-B signals ranged from -109.5 to -118 dBm depending on aircraft-satellite geometry and was approximately 18 dBm less than the direct path signal strength. With a sensitivity of -103 dBm, the CanX-7 ADS-B receiver should detect virtually all of the direct path signals while reflected signals are below the detection threshold. Although the reflected signals should not be a factor for the CanX-7 mission, they could be a consideration for a large operational satellite with a more sensitive receiver. The reception of both direct and reflected ADS-B signals from multiple aircraft could lead to signal collisions and subsequent loss of aircraft tracking information, particularly in coastal regions where there are additional sources of the 1090 MHz signal.
Highlights
Automatic Dependent Surveillance-Broadcast (ADS-B) is an air traffic surveillance technology in which aircraft routinely transmit aircraft identification, position, velocity and status during flight
A signal propagation model was created to determine the strength of direct path ADS-B signals arriving at the Canadian Advanced Nanospace eXperiment-7 (CanX-7) receiver [7]
This paper describes the method and results for ADS-B signals reflected from the ocean surface
Summary
Automatic Dependent Surveillance-Broadcast (ADS-B) is an air traffic surveillance technology in which aircraft routinely transmit aircraft identification, position, velocity and status during flight. An operational spaceborne ADS-B system would reduce aircraft spacing requirements in oceanic regions leading to more efficient routes and subsequent reductions in fuel consumption. These efforts are topical with the announcement that ADS-B receivers are planned as secondary payloads on the Iridium constellation [2], a proposed 66-satellite low Earth orbit (LEO) constellation scheduled to be deployed by late 2017. Since half of the ADS-B signals are transmitted toward the Earth, transmissions reflected from the ocean surface were considered since they could potentially double the signal density, leading to signal collisions and subsequent loss of aircraft tracking information.
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