Systems and methods for exploiting ADS-B frequency of arrival for flight surveillance, cyber security and meteorology
A system is disclosed for exploiting a transmitted signal from an aircraft to determine characteristics of any of the aircraft's motion or meteorological conditions in which the aircraft is moving. The system includes a plurality of platforms for detecting Doppler shift information of the transmitted signal at each of the plurality of platforms, and a processing system for determining characteristics of any of the aircraft's motion or meteorological conditions in which the aircraft is moving.
1. A method for exploiting a transmitted signal from an aerial vehicle, said method comprising the steps of:
receiving N frequency of arrival (FOA) signals from N collectors that detect transmission signals from an aerial vehicle during flight, the N collectors being geographically dispersed at different ranges above and below the aerial vehicle, and N being equal to at least four;
measuring N- 1 frequency difference of arrival (FDOA) signals based on the N FOA signals provided by N- 1 collector pairs to reduce an unknown frequency bias and noise associated with the transmission signals from the aerial vehicle; and
estimating a three-dimensional (3D) trajectory of the aerial vehicle based on the measured N- 1 FDOA signals,
wherein each of the FDOA signals is measured by:
estimating a transit time difference from the aerial vehicle to each of a first collector and a second collector in a collector pair based on known positions of the first collector and the second collector and an estimated position of the aerial vehicle;
time aligning the FOA signals received from the first collector and the second collector by delaying a first received one of the FOA signals by the transit time difference; and
determining the FDOA signal for the collector pair by subtracting the time aligned FOA signals from each other; and
wherein each of the foregoing steps are performed in real time during flight of the aerial vehicle.
2. The method as recited in claim 1 , wherein the transmission signals from the aerial vehicle include automated dependent surveillance broadcast (ADS-B) signals.
3. The method as recited in claim 1 , wherein the N collectors that are geographically dispersed at different ranges from the aerial vehicle include one or more spacecraft-based collectors above the aerial vehicle and one or more ground-based collectors below the aerial vehicle.
4. The method as recited in claim 3 , wherein the N collectors that are geographically dispersed at different ranges from the aerial vehicle further include one or more airborne collectors.
5. The method as recited in claim 1 , wherein estimating the 3D trajectory of the aerial vehicle based on the measured N- 1 FDOA signals includes estimating a 3D position and velocity vector of the aerial vehicle.
6. The method as recited in claim 1 , further comprising determining the estimated position of the aerial vehicle at an intersection of a plurality of geometric field of views associated with antennae of the N collectors.
7. The method as recited in claim 6 , wherein the intersection provides a curved geometric surface from which a centroid location is selected as the estimated.
8. The method as recited in claim 1 , wherein the first collector in the collector pair is a spacecraft-based collector above the aerial vehicle and the second collector in the collector pair is a ground-based collector below the aerial vehicle.