Lunar Pathfinder Minisatellite MissionDevelopment Status References
Following the European Space Agency Ministerial Council Space19+ meeting in Seville at which the UK Space Agency confirmed it will invest £374 million per year with ESA, Surrey Satellite Technology Ltd (SSTL) is pleased to announce the kick-off for the implementation phase of its Lunar data-relay spacecraft, Lunar Pathfinder. 1)
Phil Brownnett, SSTL’s Managing Director said “Lunar Pathfinder will be the first commercial service to address the need for data relay around the Moon, and will not only demonstrate an innovative business idea, but we fully expect it to also stimulate the emerging Lunar market. By pioneering a commercial solution and service delivery model in lunar orbit, SSTL and ESA are opening the door to providing services to the solar system, and contributing to the scientific progress of deep space exploration.”
The Lunar Pathfinder spacecraft is designed to provide affordable communications services to lunar missions via S-band and UHF links to lunar assets on the surface and in orbit around the Moon, and an X-band link to Earth. As early as Q4 2022, the 280 kg Lunar Pathfinder spacecraft will be a mission enabler for polar and far-side missions, which, without direct line of sight of the Earth, would otherwise have to procure their own communications relay spacecraft. Lunar Pathfinder is a more cost effective alternative to Direct-to-Earth solutions and a credible alternative to institutional deep-space ground stations, offering orbiters and near-side missions a better availability, enhanced safety and improved data-rate.
”The Moon is a cornerstone of ESA’s exploration strategy,” says David Parker, ESA’s director of human and robotic exploration, “this decade we will see humans and robots visit uncharted territory and return with new discoveries, communications is key to send scientific and operational data to Earth.”
“We are returning to the Moon with commercial and international partners, and the Lunar Pathfinder mission will be an integral part.”
To support booming demand from Lunar missions and a clear goal in the scientific community to undertake detailed study and analysis of the Aitken Basin, Lunar Pathfinder intends to operate in a stable elliptical orbit to provide 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. NASA’s Artemis program also calls for “landing the first American woman and next American man at the South Pole of the Moon by 2024, followed by a sustained presence on and around the Moon by 2028” and Lunar Pathfinder is accordingly working towards a launch in Q4 2022 to support early NASA missions.
In parallel to the Lunar Pathfinder mission SSTL has been working on future plans for a constellation of spacecraft around the Moon, capable of providing enhanced communications, as well as navigation services for the Lunar market as it grows from exploration to commercial exploitation and even tourism.
Acting both as technology and service demonstrator, Lunar Pathfinder is the opportunity for scientific and commercial mission developers to support the development, test and standardization of Lunar communication infrastructure, and for emerging off-planet telecommunications to acquire experience of lunar asset operations and off-planet service delivery. Lunar Pathfinder is thus laying the foundation to support sustainable science and exploration for the next twenty years and beyond – bringing with it the possibility that when humans next set foot on the Moon we will be hearing not “Houston we’ve landed” but instead “Guildford ....
Lunar mission services 2) 3)
The Commercial Lunar Mission Support Services (CLMSS) is a collaboration agreement between SSTL, Goonhilly Earth Station (GES) and the European Space Agency (ESA). This innovative commercial partnership aims to develop a European lunar telecommunications and navigation infrastructure to support lunar scientific and economic development, both for Europe and the rest of the world. The co-operation encompasses both the space and ground segments, and the commercial and regulatory support to catalyze the lunar economy and provide affordable access to lunar, and ultimately deep space, orbits.
• Low Cost, High Value Missions Enabler
The first offering from the partnership is a low cost service enabling new, and regular, mission opportunities to the Moon, the next frontier for commerce and sustainable solar system exploration and exploitation.
The service opens opportunities for the deployment of low cost missions into lunar orbit through the use of a high availability, high data rate communications system. This will enable science, prospecting, capability building, education and technology demonstration applications to see a greater return of high value data, acting as a multiplier in terms of benefits, while reducing the entry cost to Lunar missions.
• Through Life Mission Support Service
The first mission will offer a ride to lunar orbit for ESA payloads and nanosats, either on-board the Pathfinder spacecraft or aggregated onto the transfer stage, together with communications data relay and navigation services via Pathfinder to the GES Deep Space ground station. Future services will support customers with the integration, transportation and deployment of their payloads, offer data relay and navigation services, and a simple web-based interface for payload operations and return of mission data
• Lunar landers, rovers and surface impactors
Private and agency Lunar landers, rovers and surface impactors will also be able to sign up to use the lunar communications and navigation services provided by Pathfinder and the future constellation either for primary mission operations, to provide additional capacity, or as a back-up service. For prospecting, exploring, and ultimately utilizing the far side and poles of the Moon, a communications relay service is a mission enabler, providing the vital bridge between Earth and the lunar surface for lunar landers and rovers. Exploration of 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 Pathfinder and the future constellation 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.
• Call for Lunar Missions and Payloads
A call for lunar missions and payloads is now open and we invite you to discuss how we can meet your mission needs
• July 7, 2022: NASA will supply the upcoming European Space Agency (ESA) Lunar Pathfinder satellite with an array of laser retroreflectors, mirrored devices that reflect light back at its source. The retroreflectors will validate navigation capabilities that will be critical to the Artemis missions and future lunar exploration. 4)
- “ESA’s Lunar Pathfinder mission will help verify the performance of new lunar navigation techniques in development at NASA,” said JJ Miller, Deputy Director of Policy and Strategic Communications for NASA’s Space Communications and Navigation (SCaN) program at NASA Headquarters in Washington. “This project is built on the long collaboration between NASA and ESA within the International Committee on Global Navigation Satellite Systems (ICG), a UN forum that focuses on ensuring interoperability amongst GNSS service providers”
- Global Navigation Satellite Systems (GNSS) are the satellite constellations commonly used for position, navigation, and timing services on Earth. GPS — the GNSS constellation operated by the U.S. Space Force — is the one many Americans are familiar with and use on a daily basis.
- The Lunar Pathfinder spacecraft will host a device testing GNSS capabilities used by many to navigate on Earth, to navigate in lunar orbit. The instrument, NaviMoon, will receive signals from GPS, the U.S. GNSS constellation, and Galileo, the European GNSS constellation.
- Missions at high altitudes, like Lunar Pathfinder at the Moon, receive GNSS signals that spill past Earth’s edge from GNSS satellites on the opposite side of the planet. NASA has navigated with these faint signals as far as halfway to the Moon and plans to do so on the lunar surface with an upcoming Commercial Lunar Payload Services delivery awarded to Firefly Aerospace of Cedar Park, Texas. The lander will deliver an experimental payload, the Lunar GNSS Receiver Experiment (LuGRE), developed in partnership with the Italian Space Agency (ASI).
- “Lunar Pathfinder and LuGRE are both taking important steps toward making operational GNSS use at the Moon a reality,” said Joel Parker, LuGRE principal investigator at NASA Goddard. “By validating weak-signal GNSS for future lunar missions, we’ll provide new onboard, real-time navigation capabilities at and around the Moon using existing systems and technology.”
- Bouncing lasers off Lunar Pathfinder’s retroreflectors, engineers can validate the performance of GNSS at extreme distances. Confirming the performance of weak-signal GNSS receivers against tried and true laser ranging techniques will help missions embrace lunar GNSS navigation operationally.
- “Satellite laser ranging is one of the most accurate methods we have for measuring the distance between a spacecraft and Earth,” said A. J. Oria, SCaN GNSS expert at NASA Headquarters. “It provides an excellent reference to show how effective newer methods like weak-signal GNSS are in determining spacecraft position.”
- A laser retroreflector is a special kind of mirror that bounces laser light back towards its source, unlike a normal mirror that bounces the light off at an angle. In satellite laser ranging, a laser transmitted from a telescope on Earth reaches a retroreflector on a spacecraft or celestial body and the retroreflector bounces the light back to the telescope.
- By measuring the time a laser pulse leaves the telescope and the time the return pulse arrives, engineers and scientists can calculate precise distances between the object and a ground station. Laser ranging is more accurate than similar methods using radio waves because the wavelength of the laser light is much shorter.
- “To validate performance of weak GNSS signals: if all you have is ground radio tracking data, you're basically comparing one radio technique to another radio technique. You're not going to get any kind of precision,” said Stephen Merkowitz, Space Geodesy Project manager at NASA Goddard. “Adding laser ranging, you've got a technique that's incredibly precise and has been independently verified over the past 50 years.”
- NASA’s Goddard Space Flight Center in Greenbelt, Maryland, will furnish the Lunar Pathfinder mission with the retroreflector array with support from the U.S. National Geospacial-Intelligence Agency. The retroreflector array is designed and manufactured by Kellogg Brown & Root (KBR), a science and engineering solutions company. The Lunar Pathfinder spacecraft is being built by Surrey Satellite Technology Ltd for ESA. The NaviMoon instrument on the Lunar Pathfinder was built by Swiss GNSS receiver manufacturer, SpacePNT.
• April 20, 2022: 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 our smartphones or cars. 5)
- “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,” explains Javier Ventura-Traveset, Head of ESA’s Navigation Science Office and managing all 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 km away to an accuracy of less than 100 m. This represents an extraordinary engineering challenge, because at such a distance the faint Galileo and GPS signals it makes use of 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 UK. 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,” remarks Lily Forward, SSTL system engineer. “This engineering model receiver will be integrated into our ‘FlatSat Test Bed’ version of the mission to test 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 adds: “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” explains 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.”
Finding Ultra-faint Satnav Signals
- The satnav signals employed down 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 after they have crossed distances of more than 20 times further still, 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 keep their antennas facing Earth,” adds Pietro. “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.”
- 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.” explains Cyril Botteron, heading the company.
- “The combination of Galileo dual frequency signals with those of the existing GPS satellites is what started to make it feasible. 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.”
- 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.
- 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.
- Cyril explains: “As we experience a given acceleration the receiver can judge it is most probably at one particular point in its orbit. Usually a satnav receiver needs signals from four satellites to fix its position, but with this approach even less than four signals is still enough to obtain useful information, constraining the model to minimise any error drift.”
- European Engineering & Consultancy, EECL, in the UK was assigned the task of turning SpacePNT’s design into fully-tested hardware, additionally designing the crucial low noise amplifier that sifts through noise to boost usable signals.
- “The amplifier is a high-end custom diplexer covering the dual frequency satnav bands, hand-tuned using the best possible components and incorporating heat sink technology to further reduce unwanted noise,” says Ben Kieniewicz, ECCL founder.
- “Along with contributing to other design aspects, we also built, tested and delivered the receiver to SSTL, making use of our space-qualified cleanroom assembly and test area.”
- Lunar Pathfinder will be ready for launch at the end of 2024, offering near side, farside, orbit and polar services to missions launching in the coming years, laying the foundations for a constellation of combined telecommunications and navigation satellites around the Moon.
• September 17, 2021: ESA confirmed a contract signature yesterday with Surrey Satellite Technology Ltd (SSTL) to be the main customer for their Lunar Pathfinder satellite launching in 2024 that will provide communications services around the Moon. 6)
- A whole suite of lunar exploration missions is on the horizon, many of which have ESA involvement. These include NASA’s Artemis program, commercial lunar landers, Russia’s Luna 25 and 27 landers and the future European Large Lunar Lander (EL3).
- Lunar Pathfinder is a first step towards ESA’s ambitious Moonlight vision to create a network of communications and data relay satellites serving users worldwide. Such satellites could also provide navigation data for lunar exploration, just as today we navigate using Galileo and GPS on Earth.
- The far side and polar regions of the Moon are a particular area of interest to space agencies as a potential source of resources for water, fuel and oxygen. A communications relay satellite such as Lunar Pathfinder is necessary to ensure continuous contact for both robots and humans
- “Exploration is about discovery and returning knowledge to Earth, so in the new era of lunar exploration we require a robust and fast communications service,” says ESA’s director of Human and Robotic Exploration, David Parker. “SSTL’s Lunar Pathfinder service will be available to all, enabling lower cost lunar science, technology demonstration and commercial exploration. As a leader in lunar exploration, ESA plans to use its services extensively.”
- SSTL’s Phil Brownnett said “We are delighted to sign up ESA as our anchor customer for communication services from our Lunar Pathfinder mission. We have been collaborating with ESA since 2018 to scope Lunar Pathfinder for the commercial market, and we look forward to realizing our ambition to provide cost effective services and navigation data for users all over the world.”
- The Lunar Pathfinder mission also hosts two separate ESA experiments, the first testing the possibility of using existing navigation satellites for positioning on the Moon and the second a space weather monitor to understand radiation levels around the Moon – important for human explorers.
- Furthermore, NASA will provide a laser retro-reflector payload allowing comparison with the orbit positioning data from ESA’s navigation experiment. ESA is also discussing with NASA how Lunar Pathfinder could support its wider lunar exploration program.
- The contract was confirmed by ESA’s Director of Human and Robotic Exploration, David Parker, and SSTL’s Managing Director, Phil Brownnett, on 15 September 2021 at The Royal Society in London. Amanda Solloway, UK Government Science Minister, Josef Aschbacher, ESA’s Director General, Paul Bate, Chief Executive of the UK Space Agency, and SSTL’s Executive Chairman, Sir Martin Sweeting were also in attendance.
• September 16, 2021: The European Space Agency (ESA) has signed a contract with Surrey Satellite Technology Ltd (SSTL) for communications services from Lunar Pathfinder, due to launch in 2024. 7)
- 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. In addition, ESA is working with NASA on an agreement by which 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.
- SSTL’s Phil Brownnett said “We are delighted to sign up ESA as our anchor customer for communication services from our Lunar Pathfinder mission. We have been collaborating with ESA since 2018 to scope our Lunar Pathfinder mission for the commercial market, and we look forward to realizing our ambition to provide cost effective services and navigation data for lunar assets.”
- ESA’s David Parker said “Exploration is about discovery and returning knowledge to Earth, so in the new era of lunar exploration we require a robust and fast communications service, SSTL’s Lunar Pathfinder service will be available to all, enabling lower cost lunar science, technology demonstration and commercial exploration. As a leader in lunar exploration, ESA plans to use its services extensively.”
- Science Minister Amanda Solloway said: “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. 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.”
- For prospecting, exploring, and ultimately utilizing 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 as host a number of navigation and scientific experiments:
a) 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
b) A NASA retro-reflector to demonstrate laser ranging capabilities
c) An ESA radiation monitor to study orbital radiation conditions
- Lunar Pathfinder is supported by UK Space Agency funding via the European Space Agency (ESA) and UK company Qinetiq is working on the development of user terminals, specifically designed for compatibility to the service, for future users to plug and play.
- Lunar Pathfinder is due to operate in an Elliptical Lunar Frozen Orbit (ELFO) for an operational lifetime of 8 years. 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 X-band.
- 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. Due to the proximity of the Lunar Pathfinder spacecraft, user assets could achieve 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 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 Phase A/B1 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 services for communication and navigation around the Moon, to every lunar missions, in a sustainable way.
• September 1, 2021: SSTL has gone live with a new Lunar Mission Builder App designed to calculate the communications service a lunar mission could receive from SSTL’s Lunar Pathfinder communications spacecraft, due to launch in 2023. The new tool is available at www.sstl.co.uk/lunarapp 8)
- SSTL’s Head of Lunar Exploration, Nelly Offord said “Our ambition is to offer cost-effective and high performance communications and localisation data for lunar orbiters and surface assets, and our new app will offer an initial calculation of the communications service they could receive – that’s valuable information for the complex planning that goes into a Moon mission.”
- Lunar Pathfinder will operate in an Elliptical Lunar Frozen Orbit (ELFO) for an operational lifetime of 8 years. The spacecraft will offer two simultaneous channels of communication to lunar assets: one in S-band and one in UHF. Communications are then relayed back to Earth from Lunar Pathfinder to ground stations, using X-band. Performance, such as coverage and data-rates of the link between user asset and Lunar Pathfinder which varies depending on the location and capabilities of the user asset, can initially be assessed using the new Lunar Mission Builder App.
- For surface assets on the far side of the Moon, the use of data-relay infrastructure is essential for their missions as, without 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 lunar 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 today 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, there is an additional economical and technical benefit to using the proximity data-relay service versus direct to Earth communication; due to the proximity of the Lunar Pathfinder spacecraft, user assets could achieve higher data-rates with a lower performance, lower mass and a lower cost communication module on-board.
• March 18, 2021: ESA’s Lunar Pathfinder mission to the Moon will carry an advanced satellite navigation receiver, in order to perform the first ever satnav positioning fix in lunar orbit. This experimental payload marks a preliminary step in an ambitious ESA plan to expand reliable satnav coverage – as well as communication links – to explorers around and ultimately on the Moon during this decade. 9)
- Due for 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 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.
- Javier adds: "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.”
- This high sensitivity receiver’s main antenna was developed through ESA’s General Support Technology Program, with the receiver’s main unit developed through ESA’s NAVISP (Navigation Innovation and Support Program).
- 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 to achieve unprecedented orbit determination accuracy on an autonomous basis.”
- Lunar Pathfinder’s receiver is projected to achieve positioning accuracy of around 100 m – more accurate than traditional ground tracking.
- The availability of satnav will allow the performance of ‘Precise Orbit Determination’ for lunar satellites, notes 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. 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 go on to establish a Lunar Communication and Navigation Service.
• October 2, 2020: Just as we navigate our way around Earth's surface using the connection between our phones and navigation satellites high above us, our missions use the very same satellites to navigate their way in space. 10)
- To pinpoint a location accurately, a receiver – in our phones 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 orbit in MEO, about 22,000 km, 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 ten 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 & Preparation studies explored a seemingly radical question: could this spill over 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 were very successful, finding that indeed, 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.
- Fast-forwarding eight years, and ESA has 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 SSTL (Surrey Satellite Technology Ltd) and GES (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," adds 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. This is exciting!
- "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 & 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," notes 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."
- It is thanks to the pioneering Discovery & Preparation studies that ESA was confident enough to invest in the new receiver. This success story demonstrates the importance of investigating in blue sky research where real-world applications are not immediately apparent. Discovery & Preparation specializes in such research and is therefore pivotal in laying the path for ESA’s future activities.
• 23 October 2019: ESA and NASA reaffirmed their interest in working with commercial service providers as well as international partners on missions to the Moon in a joint statement signed at the 70th annual International Astronautical Congress last week. 13)
- The statement supports the ‘Lunar Pathfinder’ mission, ESA’s first Moon partnership with European industry, addressing communication and navigation needs for future lunar exploration.
- The ‘Lunar Pathfinder’ partnership helps lay the foundation for providing communications, navigation, and operations services around the Moon. Its communications relay service is intended to link the Earth and the lunar surface.
- “We are working together to make the commercial lunar economy a reality,” says David Parker ESA’s Director of Human and Robotic Exploration. “We want to act as an anchor customer and institutional broker for gaining access to non-European markets. ESA supports a competitive ecosystem of European space providers.”
- Commercialization is gaining momentum in the space arena and both ESA and NASA confirmed their intention to work on lunar services with the UK Space Agency earlier this year.
- In the joint statement, NASA and ESA reiterated their interest to identify the elements of this potential cooperation and formalize an interagency agreement in the future.
- The two agencies have also committed to working together to supplement NASA’s own communications capabilities with those of ESA and its partners.
- NASA also confirmed its interest in having a variety of communication and navigation services to serve its robotic missions, including lunar surface activities, starting as early as end of 2022.
• 17 April 2018: ESA has signed a collaboration agreement with Surrey Satellite Technology Ltd (SSTL) and Goonhilly Earth Station (GES) for Commercial Lunar Mission Support Services at the Space Symposium in Colorado Springs, USA. This innovative commercial partnership for exploration aims to develop a European lunar telecommunications and navigation infrastructure, including the delivery of payloads and nanosats to lunar orbit. 14)
- The partnership allows for a low-risk, phased approach to implementing a sustainable, long-term commercial service and will support lunar scientific and economic development across Europe and the rest of the world. The agreement includes the upgrade of the Goonhilly Earth Station for commercial deep space services and the development of the space segment with a lunar pathfinder mission. The cooperation also encompasses the commercial and regulatory support to catalyze the lunar economy and provide affordable access to the lunar environment, and ultimately deep space.
- The agreement was signed by Sir Martin Sweeting, founder and Executive Chairman of SSTL, Ian Jones, founder and Chief Executive of GES and David Parker, Director of Human and Robotic Exploration at ESA.
- David Parker commented, “The agreement between ESA and SSTL/GES establishes ESA’s first partnership for providing commercial services in support of lunar missions. The Lunar Pathfinder mission would provide exciting new opportunities for science and technology demonstration and open deep space access to new actors.”
- Sir Martin Sweeting commented, “I am delighted that this collaboration agreement will enable new, and regular, mission opportunities to the Moon, which I believe is the next frontier for commerce and sustainable solar system exploration and exploitation.”
- Following the recent announcement of the GES ground segment upgrade to form the world’s first deep space commercial node, the partners are now jointly committed to the developing the Lunar Pathfinder space segment for a low cost “Ride and Phone Home” capability. The Lunar Pathfinder mission will offer a ticket to lunar orbit for payloads and nanosats onboard an SSTL lunar mothership spacecraft, which will provide communications data relay and navigation services between customer payloads and the GES Deep Space ground station.
- The £1m per kilogram ticket for a flight opportunity in the 2022 timeframe includes end-to-end mission service which supports the integration, transportation and deployment of payloads, the provision of data relay and navigation services via the dedicated ESA ESTRACK deep space network, and a simple web-based interface for payload operations and return of mission data.
- Private and agency Lunar landers, rovers and surface impactors will also be able to sign up to use the lunar communications and navigation services provided by the mothership either for primary mission operations, to provide additional capacity, or as a back-up service. For prospecting, exploring, and ultimately utilizing the far side of the Moon, this 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 the mothership 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.
References1) ”SSTL Kicks-Off Lunar Pathfinder Communications Mission,” SSTL, 5 February 2020, URL: https://www.sstl.co.uk/media-hub/latest-news/2020/sstl-kicks-off-lunar-pathfinder-communications-mis
2) ”Lunar Mission Services,” SSTL, 2020, URL: https://web.archive.org/web/20200913095403/https://www.sstl.co.uk/media-hub/featured/lunar-mission-services
3) ”Lunar Mission Services,” SSTL, URL: https://www.sstl.co.uk/what-we-do/lunar-mission-services
4) Danny Baird, ”NASA Mirrors on ESA Pathfinder to Enhance Lunar Navigation,” NASA Feature, 7 July 2022, URL: https://www.nasa.gov/feature/goddard/2022/nasa-mirrors-on-esa-pathfinder-to-enhance-lunar-navigation
5) ”The Moon – where no satnav has gone before,” ESA Applications, 20 April 2022, URL: https://www.esa.int/Applications/Navigation/The_Moon_where_no_satnav_has_gone_before
6) ”Path set for commercial communications around the Moon,” ESA Science & Exploration, 16 September 2021, URL: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/Path_set_for_commercial_communications_around_the_Moon
7) ”SSTL Signs Up ESA as Anchor Customer for Lunar Pathfinder,” SSTL Press Release, 16 September 2021, URL: https://www.sstl.co.uk/media-hub/latest-news/2021/sstl-signs-up-esa-as-anchor-customer-for-lunar-pat
8) ”SSTL Launches New Lunar Mission Builder App,” SSTL Press Release, 01 September 2021, URL: https://www.sstl.co.uk/media-hub/latest-news/2021/sstl-launches-new-lunar-mission-builder-app
9) ”Galileo will help Lunar Pathfinder navigate around Moon,” ESA Applications, 18 March 2021, URL: https://www.esa.int/Applications/Navigation/Galileo_will_help_Lunar_Pathfinder_navigate_around_Moon
10) ”ESA Discovery studies lay path to navigating the Moon,” ESA Enabling & Support, 02 October 2020, URL: https://www.esa.int/Enabling_Support/Preparing_for_the_Future/Discovery_and_Preparation/ESA_Discovery_studies_lay_path_to_navigating_the_Moon
11) Information provided by Joelle Sykes of SSTL.
12) ”Lunar Mission Flyer,” a handout of SSTL, November 2019, URL: https://www.sstl.co.uk/getmedia/8a1c6876-50b4-4357-b3ce-66f990c20691/Lunar-Handout-November-2019.pdf
13) ”A pathway for communicating at the Moon,” ESA Science & Exploration, 23 October 2019, URL: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/A_pathway_for_communicating_at_the_Moon
14) ”ESA signs collaboration agreement for commercial Lunar missions,” ESA Science & Exploration, 17 April 2018, URL: https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/ESA_signs_collaboration_agreement_for_commercial_Lunar_missions
The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).
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