ESA will be the anchor customer for services from Lunar Pathfinder which will be the first dedicated lunar communications relay spacecraft when it launches in 2025. The agreement expands ESA’s and SSTL's existing commercial lunar services contract, signed in September 2021, to deliver new opportunities for lower cost lunar science, technology demonstration and exploration missions.
As part of the ongoing contract, NASA will also gain access to the services of Lunar Pathfinder, placing SSTL as a key provider of Lunar communications in the next decade.
SSTL Lunar, the Lunar Pathfinder service provider, offers lunar communications for commercial and institutional customers in support of prospecting, exploring, and ultimately utilising the far side of the Moon. Lunar Pathfinder’s communications relay service will be a mission enabler, providing the vital bridge between Earth and the lunar surface. Exploring the far side of the Moon, particularly the South Pole Aitkin Basin, is a key area for future robotic and human exploration due to its chemical and mineral composition. The stable elliptical orbit of Lunar Pathfinder will allow for long duration visibility of the Southern Lunar Hemisphere each day, with maximum opportunities for the transmission and reception of data between Earth and the lunar surface.
As well as offering communication services to orbiters and lunar surface assets, Lunar Pathfinder will also host some navigation and science experiments:
- An ESA GNSS receiver capable of detecting weak signals coming from the Earth GNSS infrastructure (GPS and Galileo), demonstrating its potential role into Lunar navigation,
- A NASA retro-reflector to demonstrate laser ranging capabilities and support the evaluation of the GNSS receiver,
- An ESA radiation monitor to collect orbital radiation data and form part of ESA’s Space Weather monitoring network.
Some of SSTL’s key technology development needed for the mission have been supported by the UK Space Agency through ESA.
For surface assets on the far side of the Moon, which are without of line of sight to the Earth, data relay services are essential to communicate “back to base”. For polar surface assets, potentially with limited direct to Earth visibility, the use of the data-relay service provides the assurance of a communication link, whenever the terrain blocks direct communication. Rovers, constrained to remain within line of sight of the lander to relay their data, will find a new independence, both in how far they can travel from the lander and how long they can survive beyond the lander’s limited lifetime.
For all lunar missions, including orbiters and near side surface assets which could manage with direct to Earth communication (DTE), there is an additional economical and technical benefit to using the proximity data-relay service. Due to the proximity of the Lunar Pathfinder spacecraft, user assets could achieve higher data-rates with a simpler, lighter and lower cost communication module on-board, compared with the equipment needed for DTE communication.
In 2018 SSTL and ESA signed a collaboration agreement for Commercial Lunar Mission Support Services and in May 2021 SSTL announced selection by the European Space Agency (ESA) to lead a feasibility Study under ESA’s Moonlight initiative which builds upon the success of Lunar Pathfinder. Fully integrated in the future lunar ecosystem, the objective of the future ESA Moonlight infrastructure is to provide sustainable commercial Lunar data-relay and navigation services around the Moon, as an enabler for future lunar missions.