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Future air navigation systems will feature international agreement on a plan for more efficient communication, navigation, surveillance and air traffic management (CNS/ATM), based heavily on satellite technology. The more dependent the global air transportation system becomes on GPS, the more vulnerable it is to disruptions in access to its signals.

Automatic Dependent Surveillance – Broadcast (ADS-B) In and Out is an essential capability within NextGen implementation plans. It is also featured in SESAR. GNSS and GPS services are essential for full ADS-B capabilities.

Combined capabilities, parallel functionalities (Galileo & GPS), and special frequencies resistant to jamming spoofing available within multi-mode receivers may be quite robust. (see RTCA documents)

Planned ADS-B coverage includes only those areas currently covered by radar. There are large regions of the airspace where there is no radar coverage.

ADS-B broadcasts are unencrypted and possibly vulnerable. (evidence, RTCA?)

Potential hazard

  1. Changes to existing procedures in certain non-normal conditions to maintain adequate safety margins
  2. Exclusive reliance on single CNS technologies, raising questions about graceful degradation and redundancy.
  3. Jamming: Intentional interference or jamming, i.e. emission of sufficiently powerful radio frequency energy. This is either realized as emission of a signal close to the GPS spectrum or if more sophisticated as emission of a GPS-like signal. Civil receivers are vulnerable.
  4. Spoofing: Is the intended injection of false GPS like signal. The receiver will lock onto a legitimate appearing signal.
  5. Failure of CNS systems to communicate changes arising from dynamically reconfigured airspace
  6. Crippling effects of Coronal Mass Ejections (solar weather) on satellite electronics and ground infrastructure
  7. Impact of man-made space debris
  8. Degradation of radio/satellite communication: During solar events, some disturbance may happen on HF and satellite communications, which would have side effects on CPDLC, ADS-C, AOC…. However, line of sight VHF communication may not be impacted.
  9. Onboard system failure due to radiation: During a radiation storm, when striking a sensitive node, radiation may induce shortcuts, change of state, or burnout in onboard electronic devices. This phenomenon is called the “single event effect”. Its impact may vary a lot from unnoticeable to a complete failure of the system. This kind of failure may become more frequent in the future because modern electronic equipment is more vulnerable to radiation due to the smaller size of their devices.
  10. Radiation doses: During radiation storms, unusually high levels of ionizing radiation may lead to an excessive radiation dose for air travellers and crew. The dose received by passengers and crew is higher at higher altitudes and latitudes.
  11. GNSS based aviation operation: High-energy particles ejected by the sun may cause strong disturbances in the upper layers of the atmosphere, mainly in the layer called the Ionosphere. This layer is composed of charged particles and is particularly sensitive to the particles ejected by the sun. The GNSS radio signals emitted by satellites have to travel through this particular layer and, under severe disturbance, are strongly affected. As a result, unexpected position and timing errors[1] can occur at the level of the user receiver. In extreme cases, the GNSS[2] receiver can lose reception of the satellite altogether and the position can no longer be computed. As a side effect, GNSS-based surveillance applications may be unavailable. SBAS or GBAS augmented services, used for approach and landing, are more demanding in terms of accuracy and integrity than the En Route/TMA GNSS-based navigation. As a consequence, the safety monitors of those systems are also more sensitive to space weather events and the unavailability of these services would be more frequent.

Corroborating sources and comments

April 3, 2014 – The U.S. Air Force is set to start early implementation of the long-anticipated GPS Civil Navigation (CNAV) message at the end of this month, and will use the process to help develop new countermeasures against spoofing.

The GPS satellites will begin the early broadcast of more accurate navigation messages on the new civil L2C and L5 signals, mainly to aid development of compatible user equipment and CNAV operational procedures. However, according to the Air Force, an element of the pre-implementation phase will evaluate new ways to protect against the growing threat of spoofing, in which vehicles can be put off course by counterfeit signals. Spoofing is a more insidious threat than jamming because users are not aware that their navigation system is being misled.

The development of spoofing countermeasures is viewed as increasingly vital because of the “safety of life” applications at which the L5 signal is aimed. L5 is the third civilian GPS signal, and will be broadcast in a radio band reserved exclusively for aviation safety services. In the future, aircraft will use L5 in combination with L1 C/A to improve both accuracy and signal redundancy. L2C is the second civilian GPS signal, and when combined in a dual-frequency receiver with the legacy L1 C/A civil signal, enables ionospheric correction that will improve accuracy. The signal broadcasts at a higher effective power than L1 C/A, which will make it easier to receive in areas where reception can be poor, such as under trees or indoors.

GPS Integrity and Potential Impact on Aviation Safety, Washington Y. Ochieng and Knut Sauer (Imperial College of Science, Technology and Medicine), David Walsh and Gary Brodin (University of Leeds) Steve Griffin and Mark Denney (The Civil Aviation Authority)

THE JOURNAL OF NAVIGATION (2003), 56, 51–65. The Royal Institute of Navigation

DOI: 10.1017/S0373463302002096

CNS/ATM SYSTEM ARCHITECTURE CONCEPTS AND FUTURE VISION OF NAS OPERATIONS IN 2020 TIMEFRAME, Dr. Satish C. Mohleji, Andrew R. Lacher and Paul A. Ostwald, Center for Advanced Aviation System Development (CAASD) The MITRE Corporation, 7515 Colshire Drive, McLean, VA 22102

Solar Storms/HEMP – From Critical Infrastructure to Business Continuity: The US Needs More Than Talking Points, Mike Cheston, Seraph, Inc., 401-524-2787,, presented at JPDO Safety Working Group meeting, January 2012

Impact of Space Weather on Aviation,

Special Report: Ultra Wideband: Killer App or App Killer?

An intriguing wireless digital technology offers to redefine how spectrum is used, but could its interference cripple other spectrum users?

UWB emissions will negatively impact GPS and FAA radar, and possibly other vital services. Tests and calculations reveal the deleterious impact UWB will have on restricted band users. GPS operates at a very low margin above the thermal noise floor and is very susceptible to UWB impulses upsetting its moderate bandwidth raw data. That is a very serious problem. The proliferation of UWB systems will compromise the functionality of the Global Positioning System.

ASRS Database Report Set Global Positioning System (GPS) Reports: a sampling of reports referencing use of Global Positioning System (GPS) devices;

May 6, 2013 – FAA Selects FreeFlight for Capstone ADS-B Project

FAA has selected FreeFlight Systems to provide upgraded automatic dependent surveillance-broadcast (ADS-B) avionics to fulfill the requirements of the second phase of its Capstone Project.  The project was originally launched in 1999 as a joint government-industry research and development effort to improve air traffic safety in Alaska, where aircraft are constantly flying in airspace beyond radar coverage. The avionics provide terrain, weather and traffic data for pilots on cockpit displays, and resulted in a 57 percent reduction in the number of aviation accidents in Alaska over a 12-year period, according to FreeFlight. The program was also meant to provide a model for the agency’s nationwide deployment of ADS-B, a fundamental equipage component of NextGen.

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