Satellite to test lunar satnav

Satellite to test lunar satnav
Technology News |
The Lunar Pathfinder satellite being developed by SSTL in the UK will orbit the Moon to provide a data link, and test out how GNSS signals could be used for navigation
By Nick Flaherty

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The European Space Agency (ESA) has signed a contract with Surrey Satellite Technology Ltd (SSTL) in the UK for a communications satellite to link the Moon and the Earth

The Lunar Pathfinder, due to launch in 2024, will orbit the Moon to provide a link back to the Earth and test out how the GNSS satellite navigation signals might be used on the Moon.

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 over an eight year lifetime.

As well as offering communication services to orbiters and lunar rovers on the surface, the Pathfinder will as host a number of navigation and scientific experiments including an ESA GNSS receiver capable of detecting weak signals coming from the Earth GNSS infrastructure (GPS and Galileo) to demonstrate its potential role into Lunar navigation. It will also carry a NASA retro-reflector to demonstrate laser ranging capabilities and an ESA radiation monitor to study orbital radiation conditions.

The spacecraft can operate two simultaneous channels of communication with lunar assets, one in S-band and one in UHF: communications are relayed back to Earth ground stations in 7 to 11.6GHz X-band.

Lunar Pathfinder is supported by UK Space Agency funding of £11.6m via the European Space Agency (ESA). UK company Qinetiq is working on the development of plug-and-play X-band user terminals specifically designed for compatibility to the service.

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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 2024. The agreement establishes ESA’s first commercial lunar services contract to deliver new opportunities for lower cost lunar science, technology demonstration and exploration missions.

ESA is working with NASA on an agreement where NASA would launch and deliver the Lunar Pathfinder spacecraft into its operational lunar orbit in exchange for data-relay services for their own missions, making NASA one of the first users of Lunar Pathfinder services.

“We have been collaborating with ESA since 2018 to scope our Lunar Pathfinder mission for the commercial market, and we look forward to realising our ambition to provide cost effective services and navigation data for lunar assets,” said Phil Brownnett, Managing Director of Airbus subsidiary SSTL.

For surface assets on the far side of the Moon, the use of data-relay infrastructure is a requirement for their missions.  Without of line of sight of the Earth, they need a data-relay service such as the one offered by Lunar Pathfinder to communicate back with Earth. 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, whatever obstacle the terrain may put between the asset and the Earth. Rovers, constrained to remain within line of sight of the lander to relay their communication, will find a new independence, both in how far they can go 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. This will allow higher data-rates with a lower performance, lower mass and lower cost communication module on-board, compared with the equipment needed for DTE communication.

In 2018 SSTL signed a collaboration agreement with ESA for Commercial Lunar Mission Support Services and in May 2021 SSTL announced selection by the European Space Agency (ESA) to lead a Phase A/B1 Study under ESA’s Moonlight initiative which builds upon the success of Lunar Pathfinder.

“Surrey Satellite Technology has taken Britain’s expertise in navigation and telecommunications to the next level. Having already delivered state-of-the-art communications services to the International Space Station, UK technology will now help sustainable return to the Moon for the first time in nearly 50 years,” said UK Science Minister Amanda Solloway. “By investing in our space sector, including £11.6m today for the Lunar Pathfinder satellite, we are helping UK companies to support major international missions, firmly securing our place as a world-leading space nation.

www.sstl.co.uk

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