The Ministerial Council of the member states of the European Space Agency (ESA) has pledged 351 million euros to ESA’s board of directors for navigation to aid in multiple satellite navigation endeavors.
This funding helps support ESA’s FutureNAV program, the Navigation Innovation and Support Program (NAVISP), and the Moonlight Initiative, developed for lunar telecommunications and navigation coverage and innovation.
The FutureNAV program is aimed at addressing the rapidly growing need for more ubiquitous, resilient and reliable positioning, navigation and timing (PNT). Its first mission consists of an initial in-orbit demonstration, small constellation of low-Earth-orbit (LEO) navigation satellites. The LEO-PNT satellites will test a multi-layer approach to deliver more accurate and robust PNT services, supplementing Galileo.
The second FutureNAV mission, GENESIS, will map the moving contours of Earth, while enhancing the accuracy of Galileo.
The expanded funding will also be invested in NAVISP. The program has already began working on over 200 projects relating to satellite navigation, PNT research, and backing Member States in research priorities.
Lastly, funding is being delegated to the Moonlight Initiative, a project designed by ESA to extend satellite navigation and telecommunications coverage to the Moon. The advancement and launch of Moonlight infrastructure on the Moon will undertake several missions bolstering future Moon exploration.
The European Space Agency (ESA) has released a new video describing the Moonlight Initiative, part of NASA’s Artemis program.
ESA is a key partner in Artemis, which aims to return people to the Moon by the end of decade. Dozens of other international public and private missions are setting their sights on the lunar surface in the coming years.
However, to achieve a permanent and sustainable presence on the Moon, reliable and autonomous lunar communications and navigation services are required. ESA is working with industrial partners on the Moonlight Initiative, to become the first off-planet commercial telecoms and satellite navigation provider.
After launch, three or four satellites will be carried into lunar orbit by a space tug, and deployed one by one to form a constellation of lunar satellites. The number and specification of these satellites are being defined.
The constellation’s orbits are optimized to give coverage to the lunar south pole, where sustained sunlight and polar ice make it the focus of upcoming missions.
Moonlight will provide data capacities sufficient to serve these planned and future missions, with a navigation service that enables accurate real-time positioning for all lunar missions.
The European Space Agency (ESA) is looking for companies interested in helping create a constellation of lunar satellites to connect and guide missions to the Moon. Creating lasting telecommunications and navigation links with the Moon will enable sustainable space exploration for the hundreds of lunar missions that are due to launch within the next few decades, ESA stated.
The companies would provide telecommunications and navigation services to these lunar missions, under its Moonlight initiative.
ESA is completing two studies with two consortia of space companies based in Europe that assess the business case and the technical solutions for building and operating a constellation of lunar satellites. ESA is asking any space firms to indicate whether they would like to become involved in the ambitious project — or simply to develop lunar telecommunication and navigation technologies and products. The deadline is Oct. 28.
Artist’s rendering: NASA
On Sept. 19, ESA Director General Josef Aschbacher and NASA Administrator Bill Nelson signed a joint statement on lunar exploration cooperation at the International Astronautical Congress in Paris.
The lunar Gateway will be an outpost in orbit around the Moon. It will serve as the staging point for both robotic and crewed exploration of the lunar south pole.
ESA’s European Service Modules will power all Artemis Orion spacecraft to the Moon and back. ESA will also provide refueling elements for Gateway and a communications module that will pave the way for Moonlight.
ESA has already initiated the Lunar Pathfinder project to provide initial communications services to early lunar missions, which will also help to prepare for the next stage with Moonlight. The Lunar Pathfinder will also include a navigation payload demonstrator, which will allow positioning in lunar orbit using GPS and Galileo systems for the first time, and is due to launch in 2025.
Space companies in Europe and Canada will be invited to tender for the initial Moonlight work in December.
The test version of a unique satellite navigation receiver has been delivered for integration testing on the Lunar Pathfinder spacecraft.
The NaviMoon satnav receiver is designed to perform the farthest ever positioning fix from Earth, employing signals that will be millions of times fainter than those used by smartphones or cars on Earth.
The NaviMoon receiver and low-noise amplifier. (Photo: SSTL)
“This engineering model of our NaviMoon receiver is the very first piece of hardware to be produced in the context of ESA’s Moonlight initiative, to develop dedicated telecommunications and navigation services for the Moon,” explained Javier Ventura-Traveset, head of ESA’s Navigation Science Office and manager of ESA lunar navigation activities.
“It will be flown aboard the Lunar Pathfinder mission into orbit around the Moon, from where it will perform the furthest satellite navigation positioning fix ever made, at more than 400,000 kilometers away to an accuracy of less than 100 meters,” Ventura-Traveset said. “This represents an extraordinary engineering challenge, because at such a distance the faint Galileo and GPS signals it uses will be barely distinguishable from background noise. This demonstration will imply a true change of paradigm for lunar orbiting navigation.”
The washing-machine-sized Lunar Pathfinder is being built as a commercial mission by Surrey Satellite Technology Ltd. (SSTL), in the United Kingdom. ESA is funding guest payloads for it, including the 1.4-kg NaviMoon receiver that will be accommodated beside the spacecraft’s main X-band transmitter that links it with Earth.
“Receiving physical hardware for a mission is always fantastic,” said Lily Forward, SSTL system engineer. “This engineering model receiver will be integrated into our FlatSat Test Bed version of the mission to test that all our systems communicate and work together properly, ahead of receiving the flight-model receiver and antenna later this year.”
This will be SSTL’s first full-fledged mission beyond Earth, she added. “Laying the foundations for numerous scientific missions that will come after it, Lunar Pathfinder is a communications relay satellite, intended to serve assets on both the nearside and farside, orbiting in an elliptical lunar frozen orbit for prolonged coverage over the South Pole — a particular focus for future exploration. Then, during regular intervals, we will orient the spacecraft towards Earth to test out the NaviMoon receiver.”
Satnav position fixes from the receiver will be compared with conventional radio ranging carried out using Lunar Pathfinder’s X-band transmitter as well as laser ranging performed using a retroreflector contributed by NASA and developed by the KBR company.
“This will be the first time these three ranging techniques will be used together in deep space,” explained ESA navigation engineer Pietro Giordano. “There is a long heritage of lunar laser ranging, going back to the Apollo missions, and the retroreflector we are using is an evolution from NASA’s Lunar Reconnaissance Orbiter. The combination of all ranging techniques will improve the orbit estimation further, potentially beyond what radio ranging can achieve.
“In principle, this could mean that future missions could navigate themselves to the Moon autonomously using satellite navigation signals alone with no help from the ground.”
The satnav signals employed here on Earth are already vanishingly faint, equivalent to a single pair of car headlights shining all across Europe. By the time these signals reach the Moon, they have crossed distances of more than 20 times further, attenuating through space like ripples from a stone splashed in water.
“Adding to the difficulty, the satnav constellations are not designed to transmit up into space, but to keep their antennas facing Earth,” Giordano said. “So we are reliant on much weaker side-lobe signals, like light spilling from the sides of a flashlight. To be able to make use of these signals, we turned to a specialist in space-based satellite navigation, whose signal-processing techniques have really proven the magic ingredient.”
Testing the NaviMoon receiver and Low Noise Amplifier engineering models at SSTL ahead of integration testing. The flight models of the receiver and amplifier will be delivered later in 2022. (Photo: SSTL)
SpacePNT, based in Switzerland, oversaw the NaviMoon receiver design. “We began working on the idea of lunar-distance satnav positioning back in 2013 as something of a scientific challenge,” said Cyril Botteron, company head.
“The combination of Galileo dual-frequency signals with those of the existing GPS satellites is what started to make it feasible,” Botteron said. “Although, along with the extreme sensitivity that is demanded, the other big problem is that from the Moon all the satnav satellites are in the same narrow geometry of sky around Earth, periodically rotating out of view.”
Lunar navigation satellites will ultimately help guide Moon landings, such as with the European Large Logistic Lander. (Image: ESA)
The solution that SpacePNT came up with leverages more than half a century of lunar exploration. The company installed a dynamic software model of all the forces acting upon the satellite into the receiver, including the gravitational influences of the Moon, Earth, Sun and planets as well as the very slight push from sunlight itself — solar radiation pressure — along with factors such as clock error and the radio signal direction.
“As we experience a given acceleration the receiver can judge it is most probably at one particular point in its orbit,” Botteron said. “Usually a satnav receiver needs signals from four satellites to fix its position, but with this approach, less than four signals is still enough to obtain useful information, constraining the model to minimize any error drift.”
European Engineering & Consultancy (EECL) in the UK was assigned the task of turning SpacePNT’s design into fully tested hardware, and also designed the crucial low-noise amplifier that sifts through noise to boost usable signals.
Artist’s impression of SSTL’s Lunar Pathfinder satellite that will provide communications services around the Moon. (Image: SSTL)
News from the European Space Agency (ESA)
ESA is going to the Moon — in collaboration with its international partners — and seeks to build a lasting lunar link to enable sustainable space exploration.
The agency has now evaluated initial ideas to create a network of lunar telecommunications and navigation satellites.
Creating a commercial telecommunications and navigation service for the Moon will allow many of the dozens of planned lunar missions to share the same infrastructure to communicate with Earth, as well as to find their way on the lunar surface.
The service is needed because the planned missions are becoming regular trips to Earth’s natural satellite rather than one-off expeditions.
Using a shared telecommunications and navigation service will reduce the design complexity and weight of individual missions, making them more cost-efficient.
Lowering the ticket price to lunar exploration could also empower a wider group of ESA member states to launch their own national lunar missions, inspiring the next generation of scientists and engineers.
Call for Ideas
The call for ideas for how to use a lasting link with the Moon is open until April 30. People working for commercial companies, universities or governmental organizations are welcome to suggest how they would like to use a lunar communications and navigation service.
This diagram presents a notional preliminary top-level system concept for a lunar communications and navigation service. (Image: ESA)
Concept Reviews Completed
Two consortia of companies have now completed their system concept reviews, which set out how to create the lunar constellation, under ESA’s Moonlight initiative to identify the best way to create a lasting link with the Moon. The reviews set out the business and technical analysis needed to identify and justify a number of feasible system concepts for creating the lunar network.
The next step will be to define a detailed system architecture and identify the most suitable partnership models between private space companies and ESA.
Telespazio leads the first consortium. The consortium includes:
satellite operators Inmarsat and Hispasat
manufacturing companies such as Thales Alenia Space Italy, OHB System in Germany and Canadian space technology company MDA
Italian Aerospace Logistics Technology Engineering Company (ALTEC)
small and medium-sized enterprises such as Nanoracks Europe and Argotec
universities and research centers such as SEE Lab, SDA Bocconi and Politecnico di Milano.
The second consortium is spearheaded by Surrey Satellite Technology Limited, both in the service prime capacity through its lunar services brand SSTL Lunar and as the satellite manufacturer. The consortium includes:
satellite manufacturer Airbus
satellite network providers SES, based in Luxembourg, and Kongsberg Satellite Services, based in Norway
the Goonhilly Earth Station in the UK
British satellite navigation company GMV-NSL.
Artemis Program and Pathfinder
NASA’s Artemis program will use several of ESA’s service modules to return humans to the Moon, including the ESPRIT communications module for the lunar Gateway’s living quarters for astronauts. With its European industrial partner, ESA is helping to build the Lunar Pathfinder, showcasing lunar communications service provision by providing initial services to early lunar missions, including a complete lunar navigation in-orbit demonstration.
The Moonlight initiative builds on both the ESPRIT communications module and the Lunar Pathfinder.
Europe’s Lunar Pathfinder mission to the Moon will carry an advanced satellite navigation receiver to perform the first satellite navigation positioning fix in lunar orbit. The experimental payload marks a preliminary step in an ambitious European Space Agency (ESA) plan to expand reliable satnav coverage — as well as communication links — to explorers around and ultimately on the Moon during this decade.
Due to launch by the end of 2023 into lunar orbit, the public-private Lunar Pathfinder comsat will offer commercial data-relay services to lunar missions, while also stretching the operational limits of satnav signals.
Navigation satellites like Europe’s Galileo constellation are intended to deliver positioning, navigation and timing services to our planet, so most of the energy of their navigation antennas radiates directly towards the Earth disc, blocking its use for users further away in space.
“But this is not the whole story,” explains Javier Ventura-Traveset, leading ESA’s Galileo Navigation Science Office and coordinating ESA lunar navigation activities. “Navigation signal patterns also radiate sideways, like light from a flashlight, and past testing shows these antenna side lobes can be employed for positioning, provided adequate receivers are implemented.”
Just like people or cars on the ground, satellites in low-Earth orbit rely heavily on satnav signals to determine their orbital position, and since ESA proved higher orbit positioning was possible, a growing number of satellites in geostationary orbit today employ satnav receivers.
But geostationary orbit is 35,786 km up, while the Moon is more than ten times further away, at an average distance of 384 000 km. In 2019 however, NASA’s Magnetospheric Multiscale Mission acquired GPS signals to perform a fix and determine its orbit from 187,166 km away, close to halfway the Earth-Moon distance.
“This successful experimental evidence provides us high confidence since the receiver we will embark on Lunar Pathfinder will have a significantly improved sensitivity, employ both Galileo and GPS signals and will also feature a high-gain satnav antenna,” Javier added.
The main challenge will be overcoming the limited geometry of satnav signals all coming from the same part of the sky, along with the low signal power.
The high-sensitivity receiver’s main antenna was developed through ESA’s General Support Technology Programme, with the receiver’s main unit developed through ESA’s Navigation Innovation and Support Programme, NAVISP.
The receiver project is led by ESA navigation engineer Pietro Giordano. “The high sensitivity receiver will be able to detect very faint signals, millions of times weaker than the ones received on Earth. The use of advanced on-board orbital filters will allow for unprecedented orbit determination accuracy on an autonomous basis,” Giordano said.
Lunar Pathfinder’s receiver is projected to achieve positioning accuracy of around 100 meters — more accurate than traditional ground tracking.
Once in a stable elliptical orbit over the lunar south pole, Lunar Pathfinder will relay signals from other Moon missions. (Image: ESA)
The availability of satnav will allow the performance of ‘Precise Orbit Determination’ for lunar satellites, said Werner Enderle, head of ESA’s Navigation Support Office. “Traditional orbit determination for lunar orbiting satellites is performed by radio ranging, using deep space ground stations,” Enderle said. “This Lunar Pathfinder demonstration will be a major milestone in lunar navigation, changing the entire approach. It will not only increase spacecraft autonomy and sharpen the accuracy of results, it will also help to reduce operational costs.”
While lunar orbits are often unstable, with low-orbiting satellites drawn off course by the lumpy mass concentrations or mascons making up the Moon, Lunar Pathfinder is planned to adopt a highly stable “frozen” elliptical orbit, focused on the lunar south pole – a leading target for future expeditions. Earth — and its satnav constellations — should remain in view of Lunar Pathfinder for the majority of testing. The main challenge will be overcoming the limited geometry of satnav signals all coming from the same part of the sky, along with the low signal power.
Lunar Pathfinder’s demonstration that terrestrial satnav signals can be employed to navigate in lunar orbits will be an important early step in ESA’s Moonlight initiative. Supported through three ESA Directorates, Moonlight will establish a lunar communication and navigation service.
“Over this coming decade, ESA aims to contribute to building up a common communications and navigation infrastructure for all lunar missions based on dedicated lunar satellites,” explained Bernhard Hufenbach, managing commercialisation and innovation initiatives for space exploration at ESA. “Moonlight will allow to support missions that cannot use Earth satnav signals, such as landers on the far side and is planning to cover the current gap towards the needs expressed by the Global Exploration community, targeting positioning accuracy below 50 meters.”
As well as facilitating lunar exploration, these satnav signals might one day become a tool for science in their own right, used, for example, to perform reflectometry across the lunar surface; sounding the scant dusty exosphere that surrounds the Moon or by providing a common time reference signal across the Moon, to be used for fundamental physics or astronomy experiments.
Javier noted that Lunar Pathfinder’s satnav experiment also will have larger consequences. “This will become the first-ever demonstration of GPS and Galileo reception in lunar orbit, opening the door to a complete way to navigate spacecraft in deep space, enabling human exploration of the Moon,” he said.
To pinpoint a location accurately, a receiver — in smartphones or on a spacecraft — needs to collect and combine signals from at least four navigation satellites. The receiver determines its distance from each of the satellites by measuring the time that it takes for the signal to travel from the satellite to the receiver.
Navigation satellites aim their antennas directly at Earth. Satellites orbiting above the navigation (GPS in this image, but Europe’s own navigation system is Galileo) constellation could only hope to detect signals from Earth’s far side. Now spacecraft can make use of signals emitted sideways from navigation antennas, within what is known as “side lobes.” Just like a torch, they shine energy to the side as well as directly forward.
Navigation satellites orbit 22,000 kilometers above Earth’s surface. As they point in the direction of Earth, any spacecraft between them and Earth are served well by their signal. But around 10 years ago, engineers started demonstrating that spacecraft outside the orbit of navigation satellites could also navigate in space using “spill over” signal from the satellites.
Then in 2012, two discovery and preparation studies explored a seemingly radical question: could this spillover signal even be used to navigate our way around the moon, and if so, what kind of receiver would we need to build to be able to use these signals?
The studies found that the signal from navigation satellites orbiting Earth could be used to navigate the moon’s surface. But with the signal being so weak, they found that a new type of receiver would need to be built, and at the time there was no clear application for this.
Eight years later, ESA invested in the development of such a receiver, and is exploring whether it could be demonstrated on the Lunar Pathfinder mission. ESA is collaborating with Surrey Satellite Technology Ltd. and Goonhilly Earth Station on this mission, which will provide exciting new opportunities for science and technology demonstration. In particular, it will help lay the groundwork for providing navigation services around the moon, currently studied through two ESA NAVISP activities and culminating in the Moonlight initiative.
“We have now accurate simulation results that show that navigation signals may be used at moon orbit and provide good performances,” said Dr. Javier Ventura-Traveset, head of the Galileo Science Office and in charge of coordinating all GNSS moon activities for ESA’s Navigation Directorate. “And with an innovative receiver in Lunar Pathfinder, we could have the first ever experimental evidence of this.
Artist’s impression of the Lunar Pathfinder mission. (Image: SSTL)
“Furthermore, we are also studying how existing navigation constellations may be complemented by additional moon-orbiting satellites, providing additional ranging signals for an optimal navigation service including moon landing and moon surface operations. This is being done as part of the ESA NAVISP program and through the ESA Moonlight initiative.”
“The discovery and preparation studies have been eye-openers and they are currently being followed up by a NAVISP activity aiming to develop the highly sensitive spaceborne navigation receiver planned to fly on board Lunar Pathfinder,” said ESA Radio Navigation Engineer Pietro Giordano. “This technology will enable improved performances and much more cost-effective ways to navigate and operate missions to and around the moon.”
