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Session A5: Aviation and Aeronautics

Characterization of Anomalies in Reported Aviation ADS-B Data from GPS Interference
Wayne W. Cooper, Ralf H. Mayer, The MITRE Corporation; Timothy S. Wallace, Federal Aviation Administration; Rick Niles, The MITRE Corporation
Date/Time: Friday, Sep. 20, 11:26 a.m.

Background
GPS interference events have a significant impact on flight operations in the contiguous United States (CONUS) airspace. During these events, the Federal Aviation Administration (FAA) must reconfigure the National Airspace System (NAS) to use the available navigation capabilities, often at the expense of capacity and efficiency. GPS interference can be further categorized as the result of the introduction of radio transmissions which prevent reception of the signal from GPS satellites (i.e., jamming), or those which attempt to replace the reception of the true signal from GPS satellites so that the aircraft will determine an incorrect GPS-based position (i.e., spoofing). Recent well-publicized events, such as the interference with GPS-based navigation in the area around Denver International Airport (DEN) starting on January 21, 2022, and in the area around Dallas-Fort Worth International Airport (DFW) on October 18, 2022, have caused noteworthy disruptions, impacting a substantial number of aircraft.
The FAA has tasked The MITRE Corporation’s Center for Advanced Aviation System Development (MITRE CAASD) to develop algorithms which characterize observed anomalies in reported aviation Automatic Dependent Surveillance - Broadcast (ADS-B) data messages collected by the FAA from aircraft flying over CONUS. These anomalies indicate interference with the GPS satellite signals received by each aircraft and used to determine their precise four dimensional (4D) position (i.e., latitude, longitude, altitude, and time). The ADS-B messages are transmitted by each aircraft about every second and received by a network of FAA ground stations. This information is collected and provided to MITRE CAASD as an hourly data set. The anomalies can include:
1. Lower than normal values of Navigational Integrity Category (NIC).
2. Time gaps in messages received from an aircraft that identify its current 4D position.
3. Unusual variation in the inferred speed or aircraft course direction obtained by an analysis of the 4D positions of sequential ADS-B messages.
4. Excessive deviation between the 4D aircraft positions obtained from ADS-B messages and the 4D aircraft positions from FAA radar surveillance data, matching each ADS-B message to the closest in time radar position.
We are characterizing anomalous aircraft ADS-B messages to identify GPS interference which may indicate jamming or spoofing. This will be an inexact measure, as each aircraft’s GPS receiver and associated avionics reacts to GPS interference differently.
Objectives
This research will provide an objective categorization of data anomalies provided by the different methods listed above, to indicate different levels of observed GPS interference severity, from a reduced NIC value (lower interference impact, potential jamming) to large position deviations between the reported ADS-B position and the matching radar-based position (higher interference impact, potential spoofing). It will analyze the DEN and DFW area GPS interference events and compare the quantified impact on aircraft during these significant GPS interference events to normal days with similar traffic levels in these two areas when no GPS interference to aviation was observed.
Anticipated Results
The final paper will provide the quantified impact of the DEN and DFW area GPS interference events and matching “normal” dates in these airspace regions on dates with similar traffic levels as controls. Normal dates are included to show that small anomalies may exist in the reported ADS-B messages which do not indicate an ADS-B interference event. Individual aircraft impacts will be provided as illustrations as well as aggregate results for each of these events and their matching “normal” dates. An analysis of any observed differences in impacts to aircraft by category (e.g., turbofan aircraft vs. piston aircraft) will also be provided.

Key Innovative Steps and Significance of Work
This research provides an extensive analysis and the quantification of the impact of GPS interference events in the DEN and DFW areas, and comparisons to the measured impacts using the same algorithm and metrics on “normal” control dates in the same areas. The research describes how the anomalies may be categorized and quantified to further assess the significance of the GPS interference event on an aircraft and on a particular 4D airspace.
Conclusions
We anticipate that the stream of ADS-B data messages for an aircraft can be processed to identify and further categorize GPS interference events on the individual aircraft and in aggregate on a particular 4D area of airspace. This identification and categorization of such events for a particular 4D area of airspace will be applied in the near future to further enhance the existing prototype Navigation Operations and Planning Agility Suite (NOPAS), which is also under development by MITRE CAASD for the FAA.
NOTICE
This work was produced for the U.S. Government under Contract 693KA8-22-C-00001 and is subject to Federal Aviation Administration Acquisition Management System Clause 3.5-13, Rights In Data-General (Oct. 2014), Alt. III and Alt. IV (Oct. 2009).
The contents of this document reflect the views of the author and The MITRE Corporation and do not necessarily reflect the views of the Federal Aviation Administration (FAA) or the Department of Transportation (DOT). Neither the FAA nor the DOT makes any warranty or guarantee, expressed or implied, concerning the content or accuracy of these views.
For further information, please contact The MITRE Corporation, Contracts Management Office, 7515 Colshire Drive, McLean, VA 22102-7539, (703) 983-6000.
2024 The MITRE Corporation. All Rights Reserved.
Approved for Public Release; Distribution Unlimited. Public Release Case Number 24-0584.

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