The Galileo Return Link Service Provider in the Works

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). As of 2015, 42 countries participate in the operation and management of the system. The system is available to maritime and aviation users and to persons such as backcountry hikers in distress situations of all states on a non-discriminatory basis, and is free of charge for the end-user in distress. On average, about 5 persons are rescued every day with the assistance of the system. Galileo support to Search and Rescue service, herein SAR/Galileo, represents Europe’s contribution to the Cospas-Sarsat system, playing a key role of the Medium Earth Orbit Search and Rescue System, MEOSAR. The SAR/Galileo Service, with its Forward Link Alert Service is an integral part of the future MEOSAR system and ensures the detection and localization 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 Centers. In addition, the SAR/Galileo Service will also introduce a new Search and Rescue function, called the Return Link Service (RLS), which provides acknowledgment messages to distress beacons equipped with a Galileo receiver, through the Galileo E1 signal. Galileo is currently the only GNSS system planning to provide this service worldwide. Within the Galileo system, the Return Link Service Provider (RLSP) is the facility in charge of the formation of the Return Link Messages and their coordination with the Galileo system, interfacing on one side with the Cospas-Sarsat network and on the other side with the Galileo Ground Mission Segment (GMS) for the transmission of RLMs to the distress beacons through the Galileo E1 signal. Although not included in the current definition, in the future the Return Link Service could be extended to provide many other features in addition to the acknowledgment services such as: • Remote activation of beacons on boats and aircraft that have been reported missing; • Turning off beacon transmission when the SAR mission has been completed, but where it was not possible or practical to recover and turn off the beacon manually; • Changing the repetition rate of the beacon transmissions after the alert has been received and location established without ambiguity, with a view to saving battery power or reducing the beacon message traffic load on the satellite system. • Message service using the capacity offered by the Return Link Service to transmit information back to the radio beacons. The RLSP facility will be installed in the SAR/Galileo Service Centre in CNES, Toulouse where the Cospas-Sarsat French Mission Control Centre (FMCC) is also operated. CNES, in its role of SAR/Galileo Data Service Provider, will be responsible for the operation of the RLSP along with the coordination of the overall SAR/Galileo Ground Segment operations. The activities for the development of the RLSP Version 1 were officially launched on September 15th, 2016. The Galileo Programme currently expects to have the Return Link Service start of operations in the timeframe end 2018 / beginning 2019. In this paper, the authors present an overview of the main aspects of the Return Link Service, the RLSP V1 infrastructure, including the description of the V1 mission and objectives. The current early and future services which will be provided by Galileo RLS, the center functionalities, the development plan, the design drivers, the high level architecture of the RLSP Version 1 will be presented.