Artists rendering of the B-21 raider, which is being produced by Northrup Grumman for the U.S. Air Force to operate in tomorrow’s high-end threat environment. (Image: U.S. Air Force)
With assured positioning, navigation and timing (APNT) and low-Earth orbit PNT (LEO PNT) coming on strong, what does the future hold for military and commercial systems dependent on the current configuration of GPS? Should military and commercial platforms be modified to include APNT, for now, with an eye to adding LEO PNT in the future? Should they integrate these two systems, or rely on one or the other as standalone systems?
Government and industry agree that interference with GPS and all GNSS is an increasing threat as jamming and spoofing technologies evolve. This has prompted government support for APNT to bolster GPS. A Feb. 12, 2020, Executive Order required a comprehensive update to national policy on PNT services by the federal government, and by owners and operators of critical infrastructure to strengthen the resilience of critical infrastructure.
Research, development and production have improved the performance — positioning, timing and (desired) accuracy — of GNSS PNT and the ability to operate in RF-challenged environments. APNT gives the U.S. military a reliable way to further enable GPS, or to act as an alternative to it, by utilizing other sensors, such as inertial navigation systems, differential GPS, visual sensors, lidar, radar, radios and star trackers that complement GPS.
The near-term expansion of internet service to include commercial broadband LEO satellites also provides potential for robust PNT, using their waveforms as signals of opportunity (SOOP). GPS and other GNSS have an infrastructure to maintain very precise time throughout their constellations, as well as satellites with specially designed transmitters, clocks, and a waveform dedicated to the PNT function. By contrast, SOOPs are in space for another purpose and not optimized for PNT. Therefore, the challenge is to exploit features of the SOOP waveforms, designing innovative techniques to determine the range to each satellite and to provide users with reliable PNT. The approach for LEO PNT may have applications to ground troops and for aerial, munition, missile and commercial applications requiring higher levels of PNT security and integrity.
GPS receivers for future military platform designs may use a software defined radio (SDR) approach and be capable of incorporating LEO PNT signals. This technology, although designed to work standalone, can be used to complement existing navigation sensors that are typically used in navigation systems, including APNT. Expansion to the usage of multiple constellations will serve to optimize performance and resiliency in an RF-challenged environment. However, LEO satellites’ closer proximity to Earth and their signal structures allow for higher signal powers, thus are more robust against jamming. With all these separate systems or fusion by SDR, how does the receiver ensure the integrity of the signal or its accuracy? An SDR qualification test would involve an unlimited number of scenarios.
One hallmark of the GPS program is that it facilitates a thorough systems engineering effort by managing in a single location interface control documents (ICDs) for alternative systems being developed by different program offices all over the country. This makes both the integration of the systems and the development of the receivers extremely difficult and complex.
“The new SPD-7 [Space Policy Directive 7, the United States Space-based Positioning, Navigation and Timing Policy, dated Jan. 15, 2021] focusing on interoperability and APNT is a seminal document to address a realized threat and a way forward,” said Bernie Gruber, a former head of the GPS Directorate (now the Military Communications and PNT Directorate). “To that end, the combination of SDRs and data fusion potentially offer a clear advantage to utilize signal and sensor diversity, thus improving the robustness of critical PNT information.”
GMV has been selected by the European Space Agency (ESA) and the European Union Agency for the Space Programme (EUSPA) to develop the Galileo second-generation system test bed (G2STB). The G2STB will provide ESA with a key system verification and validation facility in support of its role as Galileo system development prime, enabling a wide range of Galileo system monitoring, troubleshooting, prototyping and experimentation activities.
GMV will deliver four G2STB versions over five years. Among these modules, the G2 high accuracy service (HAS) data generator and monitor aims to improve the Galileo HAS that was declared operational in January.
Other early capabilities of the G2STB include an upgraded orbit determination and time synchronization facility — capable of processing inter-satellite link data, a time service monitoring module, an integrity support message generator, a signal authentication service, an authentication validation module, an emergency warning service module, an ISL simulator and a G2G message composer.
The G2STB project aims for a smooth transition from the Galileo first-generation to the second-generation, building onto the G1G legacy system tools. The G2STB is one of the key infrastructure elements that ESA is developing for the correct functioning of the Galileo second-generation satellites.
The G2STB will eventually replace and upgrade the capabilities of the two first-generation facilities, the Galileo system evaluation equipment and the time and geodetic validation facility (TGVF-X). The latter, developed and operated by GMV over the last decade, has played a key role in monitoring the Galileo signals and system validation activities during the Galileo exploitation phase. The TGVF-X is also contributing to the early validation of new capabilities and elements being rolled out in recent and upcoming Galileo System updates.
In parallel to the development phase, the G2STB will help upgrade the network of Galileo experimental sensor stations to process new signals and capabilities to ensure the availability of a G2-capable, worldwide, multi-constellation network of receivers and bit-grabbers — independent from the operational Galileo sensor stations.
What would be required for the United States to develop and deploy a GPS high-accuracy service analogous to Galileo’s HAS?
Ismael Colomina
“Galileo HAS is a particular implementation of a PPP-RTK service. U.S. companies are already providing similar fee-based services that are even more accurate than HAS. Therefore, there is no big technical challenge for the United States to provide a GPS HAS. Actually, the European Union already provides a HAS for GPS. It is more a question of strategy for GPS policy makers: which user segment to service with a HAS-like augmentation? What about other services analogous to Galileo’s OSNMA and the upcoming CAS [commercial authentication service] for resiliency purposes? In short, a HAS-like service would just require including it in the U.S. GNSS evolution roadmap.”
— Ismael Colomina GeoNumerics
John Fischer
“The challenge is probably more political than technical. The U.S. government usually refrains from competing with commercial services. The prevailing attitude in the United States is that the private sector is more efficient than the public sector. Maybe the most practical approach is for the government to provide the authentication mechanism and open access to the data required, then allow the private sector to offer services. There isn’t a pressing need for high-accuracy GPS for transportation — it needs resiliency/reliability. However, precision agriculture needs it, so maybe sponsorship from the Department of Agriculture would be more effective than from the Department of Transportation.”
— John Fischer Orolia
Mitch Narins
“When I saw this question, my first impression (as a systems engineer) was to ask ‘For whom? For what applications? For which services?’ (Positioning? Navigating? Time/frequency?) Many have concentrated on accuracy, competing in a GNSS Olympics to see who can achieve ‘the best’ position accuracy and precision (repeatability). Finally, (thanks to Logan Scott) integrity is being pushed beyond just SBAS and GBAS, and real civil authentication of signals is being pursued. I can promise nanometers/nanoseconds if I don’t have to prove it’s true. While we finally understand the need for zero trust, we must still address loss of service by establishing real complementary PNT.”
The European Union Agency for the Space Programme (EUSPA) has announced the winners of the first myEUspace track “Submission of an Idea.” This track consists of promising theoretical ideas that leverage EU space data and have high market potential. Winners received a cash prize of €10,000 each.
The myEUspace competition is open to teams from all EU Member States plus Switzerland, Norway and Iceland. The competition offers a total prize of nearly €1 million and provides support to entrepreneurs throughout the entire innovation cycle, from early-stage start-ups to scale-ups.
While the evaluation of the prototypes track is ongoing, the competition remains open for the last track, “Submission of Products.” Applications for the final track are due April 25.
Depending on the maturity of the solution at the time of submission, entrepreneurs can compete and win in three different innovation areas: “Space My Life,” “Our Green Planet” and “Dive in Deep Tech.”
See the full list of winners by area of innovation:
“Our Green Planet”
• Spillalert: Intuitive web interface for oil spills and blackwater tank detection
• BugBit: Risk analysis platform for predicting and alerting of bark beetle outbreaks
• Push4CleanAir: SaaS pollution monitoring platform
• Detritus: Online platform and mobile app for waste-crime detection
• Orioos: Autonomous robotic solution for monitoring woody perennial crops
• Vantu: Van-lifers companion app to discover “off the beaten track” sites to camp for the night
“Dive in Deep Tech”
• DeGenS: Decentralized space-to-ground data availability for artificial intelligence (AI) using blockchain
• Climate AI for Web3: Real-world portable climate API for virtual worlds powered by AI and satellite data
• Latitudo Supersar: AI analysis, classification and interpretation of multi-sensor and multi-mission images
• WhisperCash: Person to person payments via satellite for isolated regions
• Kyck: Geospatial metaverse platform for exploring and sharing AR experiences in the physical world
“Space My Life”
• Foremca: Cryptographic methodology providing forensic digital proof
• MicroPURA: Microbial Purity to detect levels of microbial contamination in the air
• Space4CC: Monitoring actions to safeguard cultural heritage in conflict areas
• Oasis City Lab: AI tool to track urban threats
The Navigation Support Office at the Mission Control Centre of the European Space Operations Center (ESOC) has been tasked with providing independent precise orbit determination for European space missions. ESOC, which is based in Darmstadt, Germany, is a part of the of the European Space Agency (ESA). ESA aims to use high-quality signals from Galileo alongside GPS to sharpen the orbital positioning levels for future space missions.
The Navigation Support Office has used the positive results of the Copernicus Sentinel-6 mission — one of the first missions to fly a joint Galileo-GPS capable receiver, which improved positioning capabilities — to prove to ESA mission teams that future missions can harness the power of Galileo to improve positioning accuracy.
Missions in the works
Proba-3 is a precision formation flying mission that aims to launch in 2024. The mission consists of two small satellites launched together that will separate to fly in tandem to prepare for future multi-satellite missions flying as one virtual structure. This mission will require millimeter-scale positioning precision and use a variety of positioning methods, including optical, radio and laser links and GNSS such as Galileo.
The ESA-supported Lunar Pathfinder will be launched into lunar orbit in 2024 with the intent of using it as a communication satellite for future moon missions. The spacecraft will incorporate a specially designed GPS- and Galileo-capable receiver that aims to demonstrate the feasibility of positioning fixes from 400,000 km away.
The future of Galileo
Galileo serves Europe and the world with accurate and reliable navigation services as well as a catalyst for future space missions — making it a critical aspect of both everyday life and the enhancement of accurate navigation. The constellation will continue to grow with 10 more Galileo first-generation satellites planned for launch in the next few years. Second-generation Galileo satellites with enhanced capabilities are being built for testing and qualification at ESA’s European Space Technology and Research Centre as well.
The University of New South Wales has developed an advanced GNSS receiver that can receive signals from GPS and Galileo satellites across multiple frequencies. The Australian Space Agency provided funding for the project via the International Space Investment initiative.
The receiver may play a key part in the future for Australian space missions.
Professor Andrew Dempster, director of the Australian Centre for Space Engineering Research (ACSER), led the development of the receiver and notes that it is an upgrade of Kea, a receiver made in Australia and New Zealand.
“The idea was to take that work (on Kea) and upgrade it for this multi-frequency, multi-system solution,” Professor Dempster said. “We needed to scale up the performance of many of the components on the boards – in particular, where the digital processors and hardware live.”
ACSER aims to have the receiver support upcoming satellite missions. The receiver can provide precise positioning, timing and velocity information. It enables satellites to produce higher quality images from space with better pointing.
As a part of the NASA Commercial Lunar Payload Services initiative, Firefly Aerospace will land the Blue Ghost lander on the lunar surface in 2024. Onboard, the Lunar GNSS Receiver Experiment (LuGRE) payload will determine whether signals from two GNSS constellations can reach the lander and provide precise navigation on the moon for future missions.
During a 12-day mission in the moon’s Mare Crisium basin, LuGRE will obtain the first GNSS fix on the lunar surface and receive signals from both GPS and Galileo. The LuGRE payload is managed by NASA’s Space Communications and Navigation program office.
This payload is a collaborative effort between NASA and the Italian Space Agency to expand the capabilities of Earth-based navigation systems. Navigation engineers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have been testing the payload’s GNSS receiver and low noise amplifier. The receiver was developed and built by the Italian company Qascom.
These components will be critical to LuGRE obtaining signals from the GPS and Galileo satellites. To prepare for operating on the moon, NASA engineers used a GNSS simulator to test and configure the payload to accurately receive and process the signals.
The LuGRE payload GNSS receiver and low noise amplifier. (Image: NASA/Dave Ryan)
The Goddard team delivered in February the flight hardware to Firefly Aerospace in Cedar Park, Texas, where it will be integrated into the Blue Ghost lander.
Astronauts and rovers traversing the lunar surface will need precise location and tracking data for their exploration endeavors. The data gathered from the LuGRE payload will be used to further develop GNSS-based navigation systems for future missions to the moon.
GPS is the gold standard for precise positioning, navigation, and timing (PNT), impacting the lives of more than six billion users worldwide. The United States economy alone depends on the free, government-provided service across 900 million GPS receivers supporting vehicle navigation systems, general aviation, financial transactions, the electrical grid, precision agriculture, surveying and construction. The GPS enterprise must remain consistent and reliable, while keeping pace with emerging technology without interruption for the end user.
Space Systems Command (SSC) at Los Angeles Air Force Base in El Segundo, California — the U.S. Space Force’s space development, acquisition, launch and logistics field command — is responsible for maintaining and modernizing the GPS enterprise. The enterprise consists of three segments: the space segment, the control segment and the user segment. Each achieved specific milestones during an exciting and productive 2022.
A new MGue for warfighters is moving closer to completion. (Image: EvgeniyShkolenko/iStock /Getty Images Plus/Getty Images)
Space Segment
There are currently 37 GPS satellites on-orbit with 31 set healthy. The constellation requires 24 operational satellites for worldwide coverage and a receiver needs to receive transmissions from four of them to determine its position in three dimensions. GPS continues to operate impressively with an average 45-cm accuracy throughout the past year with the most precise day on record at 31.5 cm. The space segment of GPS modernization focuses on GPS III and GPS IIIF satellite development with significant milestones rounded out in 2022.
For GPS III, after the successful launch of Space Vehicle 5 (SV05) on June 17, 2021, it was set healthy (usable) on May 25, 2022. The significance of SV05 is its full operational capability of the improved civilian L2 (L2C) signal. L2C improves service speed for commercial users via access to two frequencies, improves accuracy when combined with legacy civil GPS signals (L1 C/A), and is less susceptible to ionospheric interference. SV05 is the 24th satellite enabled with the Military Code (M-code), providing worldwide M-code coverage. M-code is designed to give military receivers better defense against jamming, improved accuracy, a more secure and flexible cryptography architecture, and the ability to detect and reject false signals.
On Jan. 18, 2023, SV06 successfully launched into orbit aboard a SpaceX Falcon 9 Block 5 rocket from Cape Canaveral Space Force Station, Florida. The launch of SV06 marks a key step in the larger goal of modernizing the GPS constellation. Additionally, the 10th and final satellite in the GPS III fleet finalized production and has a target launch date of 2026. GPS III Space Vehicles 7–10 are in storage and available for launch.
The next generation of GPS satellites continues development. The October 2022 contract award for GPS III Follow-On (GPS IIIF) satellites will onboard additional capabilities. In addition to introducing new civil signals designed to enhance search-and-rescue efficacy and aviation safety, laser retroreflector array for precise ranging, and a fully digital navigation payload, the GPS IIIF satellites will offer a new Regional Military Protection (RMP) capability providing up to 60 times greater anti-jamming measures. A new port on the Lockheed Martin LM2100 Combat Bus supports a substantial increase in flexibility, providing rapid integration of payloads in response to emerging threats in space.
GPS Enterprise interrelated segments. (Image: Space System Command)
Control Segment
The Next Generation Operational Control System (OCX) will replace the current GPS Operational Control System (OCS), supporting the latest U.S. Department of Defense standards and practices for cybersecurity. The updated system includes a modernized and expanded monitor station network, improved anti-jam capabilities, and enhanced operational capability to control modernized military signals.
In March 2022, OCX completed its fourth and final legacy ground antenna element (LGAE) installation on Kwajalein Island in the Republic of the Marshall Islands. OCX Block 1 and 2 are undergoing Hewlett Packard (HP) Formal Qualification Test (FQT). This event will qualify much of the system’s previously certified mission software functions. The event will also demonstrate system maturity and readiness for system acceptance, operator training, and specific developmental testing milestones with both GPS space and user segments.
The next-generation control system, OCX 3F, will modify OCX Blocks 1 and 2 to use the enhanced capabilities of GPS IIIF satellites. OCX 3F received Milestone B and Acquisition Program Baseline (APB) approval from the Milestone Decision Authority (MDA) and was authorized to enter the Engineering and Manufacturing Development (EMD) phase in May. In November, the OCX 3F program deployed 3F mission software into OCX’s Near Operations Environment (NOE) for the first time after completion of the program’s first Integration Readiness Review (IRR). The IRR event ensures that the software meets integrity standards and receives approval to be integrated and tested on the NOE prior to software releases to the operational users. OCX 3F anticipates achieving operational acceptance in 2027.
The GPS III government and industry team recently core mated GPS III SV10 and nicknamed it “Hedy Lamarr” after the actress and inventor. (Image: Lockheed Matin)
User Equipment Segment
Among the arsenal of GPS user equipment, very few pieces have the technology to use the M-code signal. Maintaining a competitive advantage against the adversary requires use of these signals; the GPS Enterprise is focused on developing Modernized GPS User Equipment (MGUE) capable of accessing these signals. The MGUE program is a joint service program developing modernized M-code-capable military GPS receivers. The program is broken into two increments (Inc 1 and Inc 2). Both are designed to deliver secure PNT performance, allow navigation warfare operations, enhance anti-jam, enhance anti-spoof and anti-tamper, and enable Blue Force Electronic Attack.
As part of the multiple elements under the MGUE Inc 1 umbrella, L3Harris delivered its final Build 7 ground card to the government on Nov. 16, 2021, and completed regression testing on that kit in February 2022. The final Delta Security Certification and Approval were completed on April 13 and April 29, 2022, respectively. Development of the L3H Ground-Based GPS Receiver Applications Module (GB-GRAM-M) card, which delivers geolocation and precise positioning capabilities for space-constrained applications while providing increased security and anti-jam capabilities, is complete and available for services procurement. MGUE Inc 1 completed qualification testing for the aviation and maritime cards on Sept. 9, 2022, with updated software builds. This build allows the program to progress to 98% of the requirements verified and enables B-2 Bombers and Guided Missile Destroyers (DDG) to continue progress toward operational testing. Completion of this commitment means significant progress toward operational testing for stakeholders and warfighters.
MGUE Inc 2 held Preliminary Design Reviews for the Miniature Serial Interface (MSI) in summer 2022, bringing the project another step closer to finalizing the EMD phase. Once all closure and action items are completed for the reviews, the government will consider each event complete. Critical Design Review (CDR) is scheduled for this summer and will validate the system design and the ability to meet system performance requirements. MGUE Inc 2 continues to execute the second competitive objective under Phase I for the Joint Modernized Handheld component; the effort is moving closer to completion of the handheld prototype and will ultimately make for a more seamless transition to operations.
GPS ground antenna at Schriever Space Force Base in Colorado. (Image: U.S. Air Force)
Conclusion
The SSC’s mandate is paramount to maintaining our modern way of life. The space professionals dedicated to developing GPS technology are committed to delivering advanced capabilities to the warfighter, the civil sector, and the world. An interconnected world is ready for us. We’re on our way.
SSC is the U.S. Space Force field command responsible for acquiring and delivering the capabilities needed by warfighters to protect our nation’s strategic advantage in and from space. It manages an $11B budget for the U.S. Department of Defense and works in partnership with joint forces, industry, government agencies, academic and allied organizations to outpace emerging threats.
For analogous updates on the other three GNSS constellations, please see:
An artist’s impression of a Moon exploration scenario. (Image: ESA)
As there are several missions to the moon planned within the next decade, space agencies have started to consider how to keep time on the moon. To address time concerns, the LunaNet architecture, designed for lunar communications and navigation services, was introduced at the ESTEC technology center of the European Space Agency (ESA) in the Netherlands in November 2022.
“LunaNet is a framework of mutually agreed-upon standards, protocols and interface requirements allowing future lunar missions to work together, conceptually similar to what we did on Earth for joint use of GPS and Galileo,” said Javier Ventura-Trav
eset, ESA’s Moonlight navigation manager, coordinating ESA contributions to LunaNet. “Now, in the lunar context, we have the opportunity to agree on our interoperability approach from the very beginning, before the systems are actually implemented.”
“During this meeting at ESTEC, we agreed on the importance and urgency of defining a common lunar reference time, which is internationally accepted and towards which all lunar system and users may refer,” said Pietro Giordano, ESA navigation system engineer. “A joint international effort is now being launched towards achieving this.”
Each mission to the moon has operated on its own timescale from Earth. Deep space antennas have been used to keep onboard chronometers synchronized with terrestrial time at the same time to facilitate two-way communications. ESA stated that this way of working will not be sustainable in the coming lunar environment.
Time to think about time
Should a single organization be responsible for setting and maintaining lunar time? Also, should lunar time be set on an independent basis on the moon or kept synchronized with Earth? And what about time on other planets?
“Of course, the agreed time system will also have to be practical for astronauts,” said Bernhard Hufenbach, a member of the Moonlight Management Team from ESA’s Directorate of Human and Robotic Exploration. “This will be quite a challenge on a planetary surface where in the equatorial region each day is 29.5 Earth days long, including freezing fortnight-long lunar nights, with the whole of Earth just a small blue circle in the dark sky. However, having established a working time system for the moon, we can go on to do the same for other planetary destinations.”
To efficiently collaborate, the international community will have to settle on a common “selenocentric reference frame,” similar to the role played on Earth by the International Terrestrial Reference Frame, allowing the consistent measurement of precise distances between points across the planet.
Space Systems Command (SSC) has declared GPS III Space Vehicle 10 (SV10) available for launch, marking completion of constellation modernization efforts and production for the GPS III program.
“The completion of the tenth, and final, GPS III space vehicle is a significant milestone for GPS modernization,” said Scott Thomas, GPS III program manager for the GPS Space Vehicles Acquisition Delta within SSC’s Military Communications and PNT directorate. “This would not have been possible without the collaboration, communication, and accountability of our industry and government partners. The GPS III program contributions underpin U.S. national security needs for our warfighters and for more than four billion GPS users worldwide.”
GPS III satellites deliver enhanced performance and accuracy through a variety of improvements, including increased signal protection with improved accuracy. GPS III also delivers a new L1C signal designed for interoperability with similar GNSS, and expands the civilian L5 signal, dubbed safety-of-life, which is not yet operational.
GPS III SV06 was launched on a SpaceX Falcon 9 Block 5 vehicle on Jan. 18, and Operational Acceptance was declared on Jan. 31. GPS III SV07, SV08, SV09 and SV10 are awaiting launch at Lockheed Martin’s GPS III processing facility in Waterton, Colorado.
GPS III Space Vehicle 06 (SV06) reached Operational Acceptance on Jan. 31 according to the Space Systems Command (SSC) of the United States Space Force. SV06 was launched on a SpaceX Falcon 9 Block 5 vehicle on Jan. 18.
SSC also transferred Satellite Control Authority (SCA) of SV06 to the 2nd Space Operations Squadron at Schriever Space Force Base, Colorado. GPS III SV06 joins the GPS PNT constellation of 31 operational satellites.
This is the first time SCA and Operational Acceptance has occurred on the same day enabling faster delivery for users. SSC’s Military and Communication positioning, navigation and timing (PNT) enterprise collaborated with the U.S. government acquisition team, industry and space operators on the achievement.
“The Operational Acceptance of GPS III SV06 further contributes to SSC’s ongoing modernization efforts, as it brings our overall suite of capabilities ever closer to our target dates for deployment to the warfighter,” said Col. Heather J. Anderson, transition director within SSC’s PNT directorate. “GPS III SV06 will be set healthy to all global users in February 2023.”
The first-stage booster used in the SV06 launch previously sent the NASA Crew-5 mission to the International Space Station on Oct. 5, 2022.
The European Union Space Programme Agency (EUSPA) has signed a framework contract entrusting France’s space agency with providing Galileo search-and-rescue (SAR) services. The 137 million euro 10-year contract includes maintaining assets in operational condition, coordinating with the host sites and interfacing with the Cospas-Sarsat community.
Image: EUSPA
The National Centre for Space Studies (CNES) has been responsible for operations of SAR-Galileo services for the European Union since 2016, providing the SAR-Galileo Forward Link Service and the Return Link Service. The coordination of operations and maintenance of the ground segment, deployed across Europe, is headquartered at the space center in Toulouse, France.
A network of reference beacons enables evaluation of the performance of the systems in real-time. CNES also provides its expertise to EUSPA for the definition of international standards, performance monitoring and future developments.
Emergency position-indicating radio beacon-based services is an addition to the framework contract. CNES has already been identified as the future operator of the Emergency Warning Service, an alert service for European communities scheduled to begin operations in 2024.
