The GALILEO Return Link Service Operational Concept

Sylvain Delattre, Chiara Scaleggi, Maxime Fontanier, Antonio Rolla, Javier Perez-Bartolome, Jeremie Benoist, Pol Novell

Abstract: The International Cospas-Sarsat Programme is a satellite based Search and Rescue (SAR) distress alert detection and information distribution system. Conceived as an international, humanitarian SAR system, it was constituted as an intergovernmental organization in 1988 by Canada, France, the USA and the former USSR (replaced by the Russian Federation in 1992). Today, more than 40 countries participate in the operations and the management of the system. European Union’s contribution to the Cospas-Sarsat system, called SAR/Galileo, is made through the Galileo Programme. It encompasses the provision of SAR transponders on-board the Galileo constellation and a geographically distributed ground segment across the European territories. Following the declaration of the Galileo Initial Services in December 2016, this contribution is playing a key role in the Cospas-Sarsat Medium Earth Orbit Search and Rescue system, the MEOSAR. The SAR/Galileo Forward Link Service is an integral part of the MEOSAR system and ensures the detection and localisation of the beacon distress signals through the relay of these signals by the Search and Rescue repeaters on board the Galileo satellites, their reception by the ground stations called MEOLUTs and alerts transmission to the Mission Control Centres (MCC). Soon the Galileo Programme will introduce a new functionality uniquely offered by SAR/Galileo to the Cospas-Sarsat system, called the Return Link Service (RLS). This service provides a communication link towards an activated beacon in distress, allowing relaying of acknowledgement messages through the Galileo L1 navigation (I/NAV E1) signal to compatible distress beacons worldwide. The RLS is provided by a dedicated facility called the Return Link Service Provider (RLSP), hosted and operated by the French Space Agency (CNES) in Toulouse, France. This facility acts as an interface between the Cospas-Sarsat and the Galileo systems : it receives the return link requests from the Cospas-Sarsat Mission Control Centres and prepares the Return Link Message (RLM) to be communicated to the Galileo Ground Mission Segment (GMS) for the transmission through the Galileo L1 signal in space. The main functions of the RLSP are summarized below: • Autonomous management of the RLM (system acknowledgment or Type-1), being the RLSP uniquely responsible for the transmission of a Return Link Message to the emitting beacon once the RLM request has been received and once the location of the alert has been confirmed by the Cospas-Sarsat; • Operations on 7d/24h basis. • Establish specific operational interfaces to: o Receive RLM requests from the French Mission Control Centre (FMCC); o Deliver RLM requests to the GMS and exchange auxiliary data with it; o Select, based on the estimated beacon location, the two most suitable Galileo satellites aiming to maximize the RLM reception probability by the beacon in distress. The development of the RLSP system started end of 2016 and was qualified by the end of 2018. In parallel, the RLS operations were prepared by the French Space Agency, taking into account: • High availability requirements (99,95 % for the RLSP infrastructure), • Strict security and accreditation constraints , • Integration into the current operational SAR/Galileo Forward Link Service without disruptions. In this paper, the authors will provide an overview of the RLSP V1 infrastructure and the associated operational concept. The concept will be described from the Cospas-Sarsat system point of view, from the distress message emission to the return link message reception. In addition, the authors will provide details of the operational concept seen from the RLS provider perspective, describing the actual organisation of the operations and the readiness status to enter into service. Note: © 2019 - European GNSS Agency The paper has been elaborated in the frame of the European Union Programme Galileo. It reflects only the authors’ view. The European Commission, in its quality of Galileo Programme Manager, is not responsible for any use that may be made of the information it contains.
Published in: Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019)
September 16 - 20, 2019
Hyatt Regency Miami
Miami, Florida
Pages: 1566 - 1582
Cite this article: Delattre, Sylvain, Scaleggi, Chiara, Fontanier, Maxime, Rolla, Antonio, Perez-Bartolome, Javier, Benoist, Jeremie, Novell, Pol, "The GALILEO Return Link Service Operational Concept," Proceedings of the 32nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2019), Miami, Florida, September 2019, pp. 1566-1582.
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