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.
Collaboration powers GPS and Galileo navigation experiment
By Danny Baird NASA’s Goddard Space Flight Center
As the Artemis missions journey to the Moon and NASA plans for the long voyage to Mars, new navigation capabilities will be key to science, discovery and human exploration.
Through NASA’s Commercial Lunar Payload Services initiative, Firefly Aerospace of Cedar Park, Texas, will deliver an experimental payload to the Moon’s Mare Crisium basin. NASA’s Lunar GNSS Receiver Experiment (LuGRE) payload will test a powerful new lunar navigation capability using Earth’s GNSS signals at the Moon for the first time.
“In this case, we are pushing the envelope of what GNSS was intended to do — that is, expanding the reach of systems built to provide services to terrestrial, aviation, and maritime users to also include the fast growing space sector,” said J.J. Miller, deputy director of Policy and Strategic Communications for NASA’s Space Communications and Navigation (SCaN) program. “This will vastly improve the precision and resilience of what was available during the Apollo missions, and allow for more flexible equipage and operational scenarios.”
LuGRE — developed in partnership with the Italian Space Agency (ASI) – will receive signals from both GPS and Galileo, and use them to calculate the first-ever GNSS location fixes in transit to the Moon and on the lunar surface.
“Space missions close to Earth have long relied on GNSS for their navigation and timekeeping,” said Joel Parker, LuGRE principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “In recent years, NASA and the international community have pushed the boundaries of what was considered possible by using these techniques in the Space Service Volume and beyond.”
This graphic details the different areas of GNSS coverage. (Image: NASA/Danny Baird)
Missions in the GNSS Space Service Volume — from about 1,800 miles to 22,000 miles in altitude — receive signals that spill past Earth’s edge from GNSS satellites on the opposite side of the planet. The first Space Service Volume experiments occurred around the dawn of the new millennium. Since then, numerous missions in the Space Service Volume have reliably used GNSS to navigate.
In 2016, the NASA’s Magnetospheric Multiscale Mission (MMS) employed GPS operationally at a record-breaking 43,500 miles from Earth. Then, in 2019, MMS broke its own record by fixing its location with GPS at 116,300 miles from Earth — nearly halfway to the Moon.
At these extreme altitudes, missions need extremely sensitive GNSS receivers. The LuGRE mission will use a specialized weak-signal receiver developed by Qascom, an Italian company specializing in space cybersecurity and satellite navigation security solutions, and funded by ASI.
LuGRE teams are now testing the payload in preparation to deliver it for integration onto the Firefly “Blue Ghost” lander in November of this year. Launch is slated for no earlier than 2024 from Cape Canaveral, Florida, aboard a SpaceX Falcon 9 rocket.
During the multi-week flight to the Moon, LuGRE will collect GNSS signals and perform navigation experiments at different altitudes and in lunar orbit. After landing, LuGRE will deploy its antenna and begin 12 days of data collection, with the potential for extended mission operations. NASA and ASI will process and analyze data downlinked to Earth, and then share results publicly.
“LuGRE is the latest effort in a long line of missions designed to expand high-altitude GNSS capabilities,” said Fabio Dovis, LuGRE co-principal investigator, ASI. “We’ve developed a cutting-edge experiment that will serve as the foundation for operational GNSS systems at the Moon.”
The LuGRE mission seeks to spark further development of GNSS-based navigation capabilities near and on the Moon, even as NASA plans to begin using high-altitude GNSS operationally for future lunar missions. NASA and ASI will bring the results of this work forward to the space community through the International Committee on GNSS, a United Nations forum focused on ensuring the interoperability of GNSS signals. These capabilities are also a key stepping stone towards building LunaNet, an architecture that will unify cooperative networks into seamless lunar communications and navigation services.
Artistic rendering of LuGRE and the GNSS constellations. In reality, the Earth-based GNSS constellations take up less than 10 degrees in the sky, as seen from the Moon. (Image: NASA/Dave Ryan)
“The lunar deliveries we’re sourcing from commercial vendors are providing a number of innovative new technologies and opportunities to conduct experiments with affordable access to the lunar surface,” said Jay Jenkins, Commercial Lunar Payload Services Program executive. “LuGRE is one example of the progress that government and industry can make when united in their exploration objectives.”
Developing new uses of GNSS for emerging space operations is a priority for the SCaN program at NASA headquarters, as the lead organization responsible for implementing guidance from Space Policy Directive-7, which directs NASA to develop requirements for GPS support of space operations and science in higher orbits and beyond into cislunar space.
Space communications and navigation engineers at NASA are evaluating the navigation needs for the Artemis program, including identifying the precision navigation capabilities needed to establish the first sustained presence on the lunar surface.
“Artemis engages us to apply creative navigation solutions, choosing the right combination of capabilities for each mission,” said Cheryl Gramling, associate chief for technology in the Mission Engineering and Systems Analysis Division at Goddard Space Flight Center in Greenbelt, Maryland. “NASA has a multitude of navigation tools at its disposal, and Goddard has a half-century of experience navigating space exploration missions in lunar orbit.”
Alongside proven navigation capabilities, NASA will use innovative navigation technologies during the upcoming Artemis missions.
“Lunar missions provide the opportunity to test and refine novel space navigation techniques,” said Ben Ashman, a navigation engineer at Goddard. “The Moon is a fascinating place to explore and can serve as a proving ground that expands our navigation toolkit for more distant destinations like Mars.”
Illustration of NASA’s lunar-orbiting Gateway and a human landing system in orbit around the Moon. (Image: NASA)
Ultimately, exploration missions need a robust combination of capabilities to provide the availability, resiliency, and integrity required from an in-situ navigation system. Some of the navigation techniques being analyzed for Artemis include the following.
Radiometrics, optimetrics and laser altimetry
Radiometrics, optimetrics, and laser altimetry measure distances and velocity using the properties of electromagnetic transmissions. Engineers measure the time it takes for a transmission to reach a spacecraft and divide by the transmission’s rate of travel — the speed of light.
These accurate measurements have been the foundation of space navigation since the launch of the first satellite, giving an accurate and reliable measurement of the distance between the transmitter and spacecraft’s receiver. Simultaneously, the rate of change in the spacecraft’s velocity between the transmitter and spacecraft can be observed due to the Doppler effect.
Radiometrics and optimetrics measure the distances and velocity between a spacecraft and ground antennas or other spacecraft using their radio links and infrared optical communications links, respectively. In laser altimetry and space laser ranging, a spacecraft or ground telescope reflects lasers off the surface of a celestial body or a specially designated reflector to judge distances.
The Lunar Orbiter Laser Altimeter (LOLA) aboard the Lunar Reconnaissance Orbiter (LRO) sends laser pulses down to the surface of the Moon from the orbiting spacecraft. These pulses bounce off of the Moon and return to LRO, providing scientists with measurements of the distance from the spacecraft to the lunar surface. As LRO orbits the Moon, LOLA measures the shape of the lunar surface, which includes information about the Moon’s surface elevations and slopes. This image shows the slopes found near the South Pole of the Moon. (Image: NASA/LRO)
Optical navigation
Optical navigation techniques rely on images from cameras on a spacecraft. There are three main branches of optical navigation.
Star-based optical navigation uses bright celestial objects such as stars, moons, and planets for navigation. Instruments use these objects to determine a spacecrafts’ orientation and can define their distance from the objects using the angles between them.
As a spacecraft approaches a celestial body, the object begins to fill the field of view of the camera. Navigation engineers then derive a spacecraft’s distance from the body using its limb — the apparent edge of the body — and centroid, or geometric center.
At a spacecraft’s closest approach, Terrain Relative Navigation uses camera images and computer processing to identify known surface features and calculate a spacecraft’s course based on the location of those features in reference models or images.
NASA will use data gathered from LuGRE to refine operational lunar GNSS systems for future missions.
Weak-signal GPS and GNSS
NASA is developing capabilities that will allow missions at the Moon to leverage signals from GNSS constellations. These signals — already used on many Earth-orbiting spacecraft — will improve timing, enhance positioning accuracy, and assist autonomous navigation systems in cislunar and lunar space.
In 2023, the Lunar GNSS Receiver Experiment (LuGRE), developed in partnership with the Italian Space Agency, will demonstrate and refine this capability on the Moon’s Mare Crisium basin. LuGRE will fly on a Commercial Lunar Payload Services mission delivered by Firefly Aerospace of Cedar Park, Texas. NASA will use data gathered from LuGRE to refine operational lunar GNSS systems for future missions.
Illustration of Firefly Aerospace’s Blue Ghost lander on the lunar surface. The lander will carry a suite of 10 science investigations and technology demonstrations to the Moon in 2023 as part of NASA’s Commercial Lunar Payload Services (CLPS) initiative.
Autonomous navigation
Autonomous navigation software leverages measurements like radiometrics, celestial navigation, altimetry, terrain-relative navigation, and GNSS to perform navigation onboard without contact with operators or assets on Earth, enabling spacecraft to maneuver independently of terrestrial mission controllers. This level of autonomy enables responsiveness to the dynamic space environment.
Autonomous navigation can be particularly useful for deep space exploration, where the communications delay can hamper in-situ navigation. For example, missions at Mars must wait eight to 48 minutes for round trip communications with Earth depending on orbital dynamics. During critical maneuvers, spacecraft need the immediate decision-making that autonomous software can provide.
LunaNet navigation services
LunaNet is a unique communications and navigation architecture developed by NASA’s Space Communications and Navigation (SCaN) program. LunaNet’s common standards, protocols, and interface requirements will extend internetworking to the Moon, offering unprecedented flexibility and access to data.
For navigation, the LunaNet approach offers operational independence and increased precision by combining many of the methods above into a seamless architecture. LunaNet will provide missions with access to key measurements for precision navigation in lunar space.
Artist’s conceptualization of Artemis astronauts using LunaNet services on the Moon, a unique approach to lunar communications and navigation. The LunaNet communications and navigation architecture will enable the precision navigation required for crewed missions to the Moon and place our astronauts closer to scientifically significant lunar sites, enhancing the our missions’ scientific output. (Image: NASA/Resse Patillo)
NASA’s Space Communications and Navigation (SCaN) program is developing capabilities that will allow missions at high altitudes to take advantage of GNSS signals for timing and navigation, including the Artemis missions to the Moon.
Interoperability of the GNSS constellations will be key for spacecraft at higher altitudes where GNSS signals are less plentiful. The program will rely on the four global constellations (GPS, Galileo, GLONASS and BeiDou) and the two regional systems operated by India and Japan.
SCaN is supporting flight experiments that will help develop multi-GNSS capabilities for spacecraft, such as Bobcat-1, developed by NASA’s Glenn Research Center in Cleveland and Ohio University.
Bobcat on the Prowl
Bobcat-1, shown with its deployable antenna stowed, will experiment with the GNSS inter-constellation time offset from low-Earth orbit. (Photo: NASA)
Bobcat-1 was selected by the CubeSat Launch Initiative in 2018 to study GNSS signals from 250 miles overhead. The small satellite launched to the International Space Station aboard a Northrop Grumman Cygnus spacecraft on Oct. 2, 2020.
On Nov. 5, the space station released the CubeSat to begin its mission. The spacecraft will orbit for about nine months, measuring signals from different GNSS constellations. Engineers will use these measurements to better understand GNSS performance, specifically focusing on timekeeping variations between the constellations.
“GNSS users at high altitudes see fewer satellites,” said Bobcat Co-Principal Investigator Frank Van Grass of Ohio University. “Time offsets between the constellations can be measured by the CubeSat and provided to these users to improve their positioning performance,”
SCaN Testbed
Bobcat-1 builds on the legacy of the SCaN Testbed, which demonstrated multi-GNSS capabilities on the space station from 2012 to 2019. The GPS and Galileo Receiver for the International Space Station (GARISS) — an instrument developed in collaboration between NASA and ESA (European Space Agency) — received signals from both GPS and Galileo, the GNSS constellation operated by the European Union.
The SCaN Testbed prior to launch to the International Space Station. (Photo: NASA)
The SCaN TestBed also laid the foundation for the Lunar GNSS Receiver Experiment (LuGRE), a Commercial Lunar Payload Services payload being developed in partnership with the Italian Space Agency. The payload will receive signals from both GPS and Galileo and is expected to obtain the first-ever GNSS fix on the lunar surface.
GNSS PNT Policy and Advocacy
While NASA engineers develop the technologies necessary for multi-GNSS navigation at ever-higher altitudes, the SCaN team works with stakeholders in the U.S. government and internationally to advance GNSS interoperability in the policy sphere. They consult on the United Nations International Committee on GNSS, helping develop additional capabilities in the Space Service Volume and beyond.
NASA recently worked to publish GPS antenna patterns from GPS satellites that launched between 1997 and 2000, collaborating with the U.S. Space Force, the U.S. Coast Guard and Lockheed Martin, who built the satellites. The PNT team is also working to facilitate publication of antenna patterns for more recent GPS satellites.
With this data, mission planners can better assess the performance of GNSS in high-Earth orbit and lunar space. This forthrightness also encourages other GNSS providers to be similarly transparent.
The Goddard PNT policy team received a 2019 Agency Honor Award for their advocacy of NASA’s interests in GNSS. From let are Frank Bauer, Jenny Donaldson, J.J. Miller, Ben Ashman and Joel Parker. Not pictured, Lauren Schlenker. (Photo: NASA)
“GNSS capabilities continue to revolutionize the ways spacecraft navigate in near-Earth space and beyond,” said NASA navigation engineer Joel Parker. “NASA’s longstanding relationships with the GNSS providers have advanced these capabilities to new heights and support the Artemis missions on and around the Moon.”
By Danny Baird NASA’s Space Communications and Navigation program office
The Artemis generation of lunar explorers will establish a sustained human presence on the Moon, prospecting for resources, making revolutionary discoveries and proving technologies key to future deep space exploration.
To support these ambitions, NASA navigation engineers from the Space Communications and Navigation (SCaN) program are developing a navigation architecture that will provide accurate and robust position, navigation and timing (PNT) services for the Artemis missions. GNSS signals will be one component of that architecture. GNSS use in high-Earth orbit and in lunar space will improve timing, enable precise and responsive maneuvers, reduce costs, and even allow for autonomous, onboard orbit and trajectory determination.
On Earth, GNSS signals enable navigation and provide precise timing in critical applications like banking, financial transactions, power grids, cellular networks, telecommunications and more. In space, spacecraft can use these signals to determine their location, velocity and time, which is critical to mission operations.
“We’re expanding the ways we use GNSS signals in space,” said SCaN Deputy Director for Policy and Strategic Communications J.J. Miller, who coordinates PNT activities across the agency. “This will empower NASA as the agency plans human exploration of the Moon as part of the Artemis program.”
Spacecraft near Earth have long relied on GNSS signals for PNT data. Spacecraft in low-Earth orbit below about 1,800 miles (3,000 km) in altitude can calculate their location using GNSS signals just as users on the ground might use their phones to navigate.
This provides enormous benefits to these missions, allowing many satellites the autonomy to react and respond to unforeseen events in real time, ensuring the safety of the mission. GNSS receivers can also negate the need for an expensive onboard clock and simplifies ground operations, both of which can save missions money. Additionally, GNSS accuracy can help missions take precise measurements from space.
Expanding the Space Service Volume
This photograph of a nearly full Moon was taken from the Apollo 8 spacecraft at a point above 70 degrees east longitude. Mare Crisium, the circular, dark-colored area near the center, is near the eastern edge of the Moon as viewed from Earth. (Image: NASA)
Beyond 1,800 miles in altitude, navigation with GNSS becomes more challenging. This expanse of space is called the Space Service Volume, which extends from 1,800 miles up to about 22,000 miles (36,000 km), or geosynchronous orbit. At altitudes beyond the GNSS constellations themselves users must begin to rely on signals received from the opposite side of the Earth.
From the opposite side of the globe, Earth blocks much of the GNSS signals, so spacecraft in the Space Service Volume must instead “listen” for signals that extend out over the Earth. These signals extend out at an angle from GNSS antennas.
Formally, GNSS reception in the Space Service Volume relies on signals received within about 26 degrees from the antennas’ strongest signal. However, NASA has had marked success using weaker GNSS side lobe signals — which extend out at an even greater angle from the antennas — for navigation in and beyond the Space Service Volume.
Since the 1990s, NASA engineers have worked to understand the capabilities of these side lobes. In preparation for launch of the first Geostationary Operational Environmental Satellite-R weather satellite in 2016, NASA endeavored to better document side lobes’ strength and nature to determine if the satellite could meet its PNT requirements.
“Through early on-orbit measurement and documentation of the GNSS side lobe capabilities, future missions could rest assured that their PNT needs would be met,” said Frank Bauer, who began the GNSS PNT effort at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Our understanding of these signal patterns revealed a host of potential new GNSS applications.”
Navigation experts at Goddard reverse-engineered the characteristics of the antennas on GPS satellites by observing the signals from space. By studying the signals satellites received from GPS side lobes, engineers pieced together their structure and strength. Using this data, they developed detailed models of the radiation patterns of GPS satellites in an effort called the GPS Antenna Characterization Experiment.
While documenting these characteristics, NASA explored the feasibility of using side lobe signals for navigation well outside what had been considered the Space Service Volume and in lunar space. In recent years, the Magnetospheric Multiscale Mission (MMS) has even successfully determined its position using GPS signals at distances nearly halfway to the Moon.
A graphic detailing the different areas of GNSS coverage. (Image: NASA)
GNSS at the Moon
To build on the success of MMS, NASA navigation engineers have been simulating GNSS signal availability near the Moon. Their research indicates that these GNSS signals can play a critical role in NASA’s ambitious lunar exploration initiatives, providing unprecedented accuracy and precision.
“Our simulations show that GPS can be extended to lunar distances by simply augmenting existing high-altitude GPS navigation systems with higher-gain antennas on user spacecraft,” said NASA navigation engineer Ben Ashman. “GPS and GNSS could play an important role in the upcoming Artemis missions from launch through lunar surface operations.”
While MMS relied solely on GPS, NASA is working toward an interoperable approach that would allow lunar missions to take advantage of multiple constellations at once. Spacecraft near Earth receive enough signals from a single PNT constellation to calculate their location. However, at lunar distances GNSS signals are less numerous. Simulations show that using signals from multiple constellations would improve missions’ ability to calculate their location consistently.
To prove and test this capability at the Moon, NASA is planning the Lunar GNSS Receiver Experiment (LuGRE), developed in partnership with the Italian Space Agency. LuGRE will fly on one of NASA’s Commercial Lunar Payload Services missions. These missions rely on U.S. companies to deliver lunar payloads that advance science and exploration technologies.
NASA plans to land LuGRE on the Moon’s Mare Crisium basin in 2023. There, LuGRE is expected to obtain the first GNSS fix on the lunar surface. LuGRE will receive signals from both GPS and Galileo, the GNSS operated by the European Union. The data gathered will be used to develop operational lunar GNSS systems for future missions to the Moon.
Honeywell, under a contract with Lockheed Martin, will supply guidance and navigation systems for NASA’s upcoming Artemis missions, which will fly humans to the moon for the first time since 1972.
The companies are supplying key components to NASA’s Orion spacecraft fleet for the Artemis missions. Components include the barometric altimeter, the inertial measurement system, and the GPS receiver.
Honeywell will provide 14 product types for Artemis missions III through V, including both hardware and software solutions, to support NASA’s lunar missions. NASA awarded Lockheed Martin a long-term, multibillion-dollar production contract for the Orion spacecraft, aimed to meet the space agency’s anticipated needs into the 2030s.
Working in collaboration with the Orion team over the next decade, Honeywell will support Lockheed Martin and its partners through the development and production of essential guidance and navigation systems, command data handling, and display and control products. The focus of the missions is to conduct science and learn lessons that will help take humans to Mars.
Honeywell will supply the following types of technology for the Artemis missions:
First Orion Spacecraft: In this March 30 photo, Orion I is moved to the Final Assembly and Systems Test cell at Kennedy Space Center. The spacecraft returned from Ohio after a successful series of environmental tests at Glenn Research Center’s Plum Brook Station. (Photo: NASA)
• Guidance and Navigation Systems. Key navigation and guidance solutions, including the barometric altimeter, which tracks the altitude of the Orion capsule in Earth’s atmosphere, as well as the inertial measurement system (INS) and GPS receiver, which track the position and movements of the capsule.
• Command Data Handling. Several data-handling products, including the vehicle management computer, which acts as the central computing platform supporting flight and vehicle control, as well as spacecraft communication functions.
• Displays and Controls. Three display units and struts, seven control panels, and two hand controllers used inside the spacecraft to help astronauts in the Orion capsule monitor and control the vehicle.
• Core Flight Software. Includes the integrated modular avionics software, a key system responsible for supporting maintenance functions sharing flight data information.
The contract to supply key components of the Orion crew module and service module is being managed and performed out of Honeywell’s facility in Clearwater, Florida. Work is also being conducted at the company’s facilities in Glendale, Arizona, and Puerto Rico.
Honeywell was part of NASA’s previous crewed space missions, including those that took humans to the moon.
GPS could be used to pilot in and around lunar orbit during future Artemis missions.
A team at NASA is developing a special receiver that would be able to pick up location signals provided by the 24 to 32 operational GPS satellites. Such a capability could soon also provide navigational solutions to astronauts and ground controllers operating the Orion spacecraft, the Gateway in orbit around the Moon and lunar surface missions.
The advanced GPS receiver would be paired with precise mapping data to help astronauts track their locations in space between the Earth and the Moon, or on the lunar surface.
Artist’s concept of NASA’s Magnetospheric Multiscale mission consists of four identically equipped observatories that rely on Navigator GPS to maintain an exacting orbit that is at its highest point nearly halfway to the Moon. (Image: NASA)
Navigation services near the Moon have historically been provided by NASA’s communications networks. The GPS network could help ease the load on NASA’s networks, freeing up that bandwidth for other data transmission.
“What we’re trying to do is use existing infrastructure for navigational purposes, instead of building new infrastructure around the Moon,” said engineer and principal investigator Munther Hassouneh at Goddard Space Flight Center in Greenbelt, Maryland.
NASA has been working to extend GPS-based navigation to high altitudes, above the orbit of the GPS satellites, for more than a decade. The agency now believes its use at the Moon, which is about 250,000 miles from Earth, can be done.
“We’re using infrastructure that was built for surface navigation on Earth for applications beyond Earth,” said Jason Mitchell, chief technologist for Goddard’s Mission Engineering and Systems Analysis Division. “Its use for higher altitude navigation has now been firmly established with the success of missions like Magnetospheric Multiscale mission (MMS) and the Geostationary Operational Environmental Satellites (GOES). In fact, with MMS, we’re already nearly halfway to the Moon.”
Navigator GPS
The team developing a GPS receiver for use in and around lunar orbit (from left): Jason Mitchell, Luke Winternitz, Luke Thomas, Munther Hassouneh and Sam Price. (Photo: NASA/T. Mickal)
The lunar GPS receiver is based on the Goddard-developed Navigator GPS, which engineers began developing in the early 2000s specifically for NASA’s MMS mission, the first-ever mission to study how the Sun’s and Earth’s magnetic fields connect and disconnect. The goal was to build a spacecraft-based receiver and associated algorithms that could quickly acquire and track GPS radio waves even in weak-signal areas. Navigator is now considered an enabling technology for MMS.
Without Navigator GPS, the four identically equipped MMS spacecraft couldn’t fly in their tight formation in an orbit that reaches as far as 115,000 miles from Earth’s center — far above the GPS constellation and about halfway to the Moon.
“NASA has been pushing high-altitude GPS technology for years,” said Luke Winternitz, the MMS Navigator receiver system architect. “GPS around the Moon is the next frontier.”Extending the use of GPS to the Moon will require some enhancements over MMS’s onboard GPS system, including a high-gain antenna, an enhanced clock and updated electronics.
“Goddard’s IRAD (Internal Research and Development) program has positioned us to solve some of the problems associated with using GPS in and around the Moon,” Mitchell said, adding that a smaller, more robust GPS receiver could also support the navigational needs of SmallSats, including a new SmallSat platform Goddard engineers are now developing.
Building on NavCube
NavCube, which will be tested aboard the International Space Station later this year, is being used as a baseline for a lunar GPS receiver. (Photo: NASA/W. Hrybyk)
The team’s current lunar GPS receiver concept is based on NavCube, a new capability developed from the merger of MMS’s Navigator GPS and SpaceCube, a reconfigurable, very fast flight computer platform. The more powerful NavCube, developed with IRAD support, was recently launched to the International Space Station where it is expected to employ its enhanced ability to process GPS signals as part of a demonstration of X-ray communications in space.
The GPS processing power of NavCube combined with a receiver for lunar distances should provide the capabilities needed to use GPS at the Moon. Earlier this year, the team simulated the performance of the lunar GPS receiver and found promising results. By the end of this year, the team plans to complete the lunar NavCube hardware prototype and explore options for a flight demonstration.
“NASA and our partners are returning to the Moon for good,” Mitchell said. “NASA will need navigation capabilities such as this for a sustainable presence at the Moon, and we’re developing enabling technologies to make it happen.”
