In 2015, the European Commission implemented the Horizon 2020 Framework Programme for Research and Innovation in Satellite Navigation with the goal of preparing the future of Galileo. Within this context, the investigation of the next generation of Galileo satellites (Galileo 2nd Generation - G2G) is essential. In particular, the G2G satellites must have the ability to replenish the constellation when the initial Galileo FOC satellites reach end of life, as well as fulfilling the Galileo evolution objectives for the next set of Galileo satellites.
To achieve this, a dedicated Phase B0 study (H2020-ESA-021) was initiated by ESA to determine the feasibility of the space segment design to fulfil the top-level objectives. The study was conducted by ADS from January to October 2018.

The primary objectives identified for the G2G Space Segment are:

• Ensuring service over a long period of time by ensuring replenishment of the constellation.
• Improving navigation performance.
• Improving robustness at system and service level.
• Providing additional new services (timing, support to Safety of Life, SSV, SAR).
• Including flexibility to introduce new services with fast time-to-market in the future.
• Reduction of operations and lifecycle cost.

The European Commission has defined a High Level Description Document for the evolution of Galileo (eHLD) to define the mission targets and evolution of Galileo for the future (2030 and beyond). These mission scenarios were mapped to three System Evolution Scenarios.
In the assessment of the evolution scenarios, ADS critically reviewed the ESA Technical Requirements and provided inputs to assist ESA in consolidating them for the next phase. ADS conducted a variety of trade-offs at system, satellite, payload, and network levels. Based on the trade results, a set of G2G space segment concepts were defined to provide baselines for further assessment by ESA at constellation and system level. The set of technical documentation was provided to ESA and used as inputs to determine the way forward for the next generation of Galileo satellites.