The European Space Agency (ESA) low Earth orbit (LEO)-PNT satellite program, approved at last year’s (2022) ESA ministerial conference, will soon begin testing a mini-constellation of at least ten satellites, placed in orbit some hundreds of kilometers above the Earth’s surface. Conventional GNSS systems, like those used by Europe’s Galileo program, utilize medium Earth orbit (MEO) satellites, about 23,000 kilometers from Earth.
ESA believes traditional Global Navigation Satellite Systems (GNSS) are quickly approaching the limits of their potential in terms of technical performance. In a recent communication, the agency said that while GNSS will remain a fundamental backbone for positioning, navigation and timing (PNT) services, new alternatives are now required.
ESA has launched a new invitation to tender, calling on European companies to join the LEO PNT project. The call covers all aspects of orbit demonstration, including space and ground segments, system engineering aspects, operations, launch, test user segment, experimentation, and service demonstration in representative user environments.
Multi-layer satnav concept
MEO was initially selected for GNSS constellations because a couple of dozen satellites at this altitude can deliver global coverage. However, some fundamental weaknesses and vulnerabilities of such systems are now leading developers to look more seriously to back-up and complimentary PNT sources. Combining MEO and LEO GNSS constellations is now widely seen as a potential positive strategy for moving forward.
Signals from LEO PNT satellites can reach places where today’s satnav signals cannot. Adoption of novel navigation techniques and a wider range of signal bands will allow operators to address a variety of specific user needs, including more rapid position fixes, increased precision, resilience and signal penetration.
ESA’s LEO-PNT program is being supported under ESA Directorate of Navigation’s FutureNAV initiative. ESA member states currently subscribed to FutureNAV LEO-PNT are Austria, Belgium, Finland, France, Germany, Hungary, Italy, Norway, Portugal, Romania, Spain, Sweden, Switzerland, and the UK.