094 - High-accuracy formation flying technologies for future distributed space instruments

More and more advanced sensing systems implement the concepts of distributed instrumentation, in areas ranging from science to telecommunications. Typical illustrations include astronomy with optical and radio-telescopes (e.g., SKA, ALMA), underground sensing, and some implementation of massive MIMO over multiple base stations in 5G/6G networks. The opportunity of distributed instrumentation has been identified since long for space missions, motivated by the prospects of increasing mission performances without increasing the size the satellites or as enabler for some missions. Application domains include Science, Earth Observation, Exploration as well as Satellite Telecommunication where very large antenna arrays could be achieved thanks to swarm of satellites. Examples of missions include the GRACE/GRACE-FO for gravimetry, and ESA’s Proba-3 (Sun’s coronagraph by a set of two complementary satellites). The prospects of more advanced missions, in near Earth orbit inspired by the advent of largely distributed space infrastructure available at low cost, as well as in Deep space or on the Moon, introduce new horizon in terms of needs, towards 3D formation flying and high accuracy over very long baselines. This context motivates investigations of new concepts supporting one order of magnitude improvement in terms of satellite formation flying technologies for Europe.

The objective of the activity is to investigate new concepts for ultra-accurate formation flying systems with long baseline (below 1 mm level, beyond 100 km) and initiate the proof-of-concept on selected critical technologies.

The activity will study and design concepts starting from the state-of-the-art in satellite formation flying and considering cross-fertilisation with technologies currently in use or under development for terrestrial applications (e.g., platooning for vehicles and robots, device-to-device ranging, etc.).

Key drivers are the accurate knowledge of satellite relative position, clocks offsets, and attitude, enabled by accurate ranging and attitude determination among satellites using a combination of RF and optical technologies. Frequency combs might be considered in optical systems. The concept will be validated with the demonstration of the critical enabling technologies such as ranging with RF or optical links. The analysis will trade the nature of the link between RF and optical, for different ranges of accuracies mapped to representative use cases, and depending on the trade-offs, critical elements of that relevant link will be demonstrated (RF or optical).
The activity will not replicate technical solutions used in commercial developments (for example will not consider only relative/differential GNSS for ranging), with the objective to achieve the very high accuracy target stipulated and to be not exclusively dependent on GNSS.

The tasks to be performed shall include:

• Survey of the state-of-the-art (e.g., lessons-learned from formation flying missions, advances in ISL technologies, terrestrial D2D technologies such as V2V and UWB) and consolidation of the targeted performances (ranging, attitude, nature of satellite formation)
• Investigation and trade-offs among candidate technologies and concepts, towards the definition of the preferred solution (architecture, algorithms, enabling technologies) and simulation of the targeted concept performances.
• Identification of the critical building blocks to demonstrate with an early proof of  concept.
• Design, development, and validation of the early proof of concept, and feedback of the measured performances.

The main outputs of the activity will consist of:

• Survey of state of the art, study of the possible concepts, enabling technologies and associated trade-offs
• Breadboards of the critical elements and technologies
• Roadmap for technology maturation up to in-orbit demonstration, for instance in the context of future Navigation Directorate programmes