Galileo Search-And-Rescue Return-Link Implementation
for a better Civil Aviation Safety

The Cospas-Sarsat system is currently evolving towards MEO orbits, being supported by GNSS constellations (GPS, Galileo and Glonass). Each GNSS satellite is being equipped with a transparent payload that will relay the distress signals towards ground stations (MEOLUT) in charge of detecting, demodulating and localizing the distress beacon. After the Cospas-Sarsat approval process embodied by the Demonstration & Experimentation (D&E) phase, this transfer to MEO orbits will replace the current LEO system. Accompanied with a modification of beacons signal to better fit the new MEO capabilities, this deep transition will dramatically change the level of service of this global rescue service, with several key added values compared to today system. It will, indeed:  

  • Provide a real time worldwide detection and report of the localization to the rescue centre,
  • Allow an instantaneous localization determination based on a mono-burst triangulation,
  • Dramatically improve the accuracy of the localization down to 100m, compared to current 5 km, based on the increase of tracked satellites and on the adoption of a new spread spectrum modulation for the beacon with time of arrival measurements
  • Allow the determination of the localization for a high dynamic holder , such as an aircraft

Supported by the central place of France at Cospas-Sarsat Joint committee, composed of France, USA, Russia and Canada, Galileo will play a central role in the evolution of the system. Galileo will, in particular, offer an additional service, the Return-Link Service (RLS ) designed to remotely interact with the beacon. This interaction will be ensured by a dissemination of short messages in the Galileo Open Service signal to any identified beacon, which paves the way for a two-way communication link with the beacon. The definition of the RLM (Return-Link Message) and its operational usages are still under construction at Cospas-Sarst committee level as well as at ICAO level. 

Recent drama in civil aviation leading to losses of several aircrafts (AF447, MH370, etc…) have shown first an incapacity of quickly dispatching rescue means for potential survivals, and second, a surprising incapacity of determining the position of the aircrafts wreck, generating major researches expenses.

This situation led to the creation of a joint RTCA/Eurocae working area in SC229/WG98 group; Its objective: Define new solutions to cope with the current situation. It mirrors the ICAO recommendations raised during the Second High-Level Safety Conference (HLSC 2015) in Montreal, where the necessity to increase significantly the effectiveness of the current alerting and Search & Rescue services has been released. The conference raised a list a key improvement areas and paved the way for the development of an integrated system, the Global Aeronautical Distress and Safety System (GADSS) that addresses all the distress flight phases. Based on these initiatives, a regulation will impose in-flight activations of aircraft S&R beacons for 2021.

GRICAS proposes to experiment and validate a whole set of innovative operational procedures for in-flight activation of SAR beacons onboard aircrafts taking benefit of the unique Galileo SAR service and of many assets brought by the consortium:

  • A strong representation at Cospas-Sarsat level with active push actions for new beacon modulation with CNES and Thales Alenia Space (France), increasing the accuracy
  • An innovative and accurate MEOLUT, named MEOLUT-Next, that will be developed by Thales Alenia Space (France) within GRICAS
  • The aeronautical beacon worldwide leader, ELTA, who will develop a New Generation (NG) Beacon
  • A strong representation at ICAO and RTCA level to push for the adoption of the concepts (BEA, DGAC, ASECNA)

The project intends to develop a system approach and key sub-systems before testing in-flight activation concepts that are allowed by Galileo. The project will reversely turn Galileo SAR service unique relying on innovative uses of Return Link Messages that will pave the way for a better in-flight safety. 
The project will first develop a prototype of a new generation aircraft beacon (ELT) based on spread spectrum, connected to the avionics of the aircraft, New generation of MEOLUT, and then develop automatic in-flight activation concepts:

  • Detection of the aircraft leaving its flight domain
  • Detection of anomaly at GNSS receiver level (abnormal interference level, spoofing attempt, etc…)
  • Loss of connectivity with the avionics, or alert triggering by the avionics,
  • Reception of a remote activation through the Galileo RLM on request of ground segment

The project relies on a strong consortium counting on a unique presence in Civil Aviation regulation bodies, experts in SAR domains, experts in GNSS domains and market leaders all along the value chain. 

The project will also focus on how the RLM can maximize the operations efficiency, considering a low-power consumption GNSS chipset receiver to continuously maintain GNSS tracking after alert:

  • To request confirmation through the RLM to handle false alarms inherent to automatic activations,
  • To potentially interaction with aircraft equipment, etc…

To maximize the efficiency and impact of the project, it is structured in 4 distinct phases:

  • Phase 1: definition of the use cases, and operational procedures. The task will take as an input the various accidents and incidents listed by the WG98. It will define the way Galileo SAR can bring answers to the situation, and will define experimentations to be carried out.
  • Phase 2 : The definition and development of the system to be used for experimentation and striking demonstrations; New Generation beacons with embedded low power consumption GNSS receiver, New generation MEOLUT using active antenna, interconnection between the MEOLUT and the F-MCC to the RLSP in order to use the RLM, algorithms to automatically detect emergency situations.
  • Phase 3 : Experimentations and demonstrations phase, that will be made in 4 sub-phases
    • An experimental phase relying on a flight simulator connected to a real beacon activated by the flight condition and transmitting signals to the real Galileo satellites and received by the real MEOLUT,
    • A preparatory experimentation phase using a tourism bi-engine aircraft
    • A first experimental phase carried out in Toulouse with ATR in the ATR test-aircraft
    • A second experimental and demonstration phase in Dakar, carried out with ASECNA’s ATR for a dissemination over Africa.
  • Phase 4 : Finally the project will exploit the results for dissemination within the EUROCAE WG 98 group, at ICAO level, at COSPAS-SARSAT level, and of course for Galileo.

GRICAS is a unique opportunity to bring to the fore an essential Galileo differentiator compared to other GNSS, e.g. a rich SAR service with a unique Return link service, and to promote a decisive contribution of Galileo to worldwide aviation safety.

Figure 1 - GRICAS Concept