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GNSS researchers presented hundreds of papers at the 2022 Institute of Navigation (ION) GNSS+ conference, which took place Sept. 19–23 in Denver, Colorado, and virtually. The following five papers focused on lunar and space applications. The papers are available now.

MTO Navigation Using Lunar Signals

The moon transfer orbit (MTO) is becoming increasingly important as several national space agencies are planning moon exploration soon, with projects such as NASA’s Artemis. In previous research, the GPS navigation accuracy on the MTO reached 200 m at the moon altitude by using GPS signals emitted from the far side of Earth. As accuracy on a low-Earth orbit (LEO) using GPS is a few meters, 200 m accuracy is not accurate enough to support lunar exploration. The deterioration of accuracy is due to the poor geometry of the GPS satellites that became visible from the MTO.

The authors want to achieve an accuracy of less than 100 m in MTO by using other navigation sources, including the lunar navigation satellite system (LNSS) to be deployed in the moon’s orbit. The LNSS signals will come from the far side of the moon, similar to the signals of GPS satellites coming from the opposite side of Earth. Its satellites will be pointed towards the moon to provide positioning, navigation and timing services on the moon surface, especially at the lunar South Pole region

The researchers have been conducting the simulation evaluation for the MTO navigation accuracy using signals coming from the moon and assume that these signals will be emitted from beacons on the moon surface or the LNSS.

Murata, Masaya; Kogure, Satoshi; “Moon Transfer Orbit Navigation Using Signals Coming from the Moon.”

Designing the Smallsat-Based LNCSS

There is growing interest in the use of a smallsat platform for the future lunar navigation and communication satellite system (LNCSS); however, many design considerations are not finalized for the smallsat-based LNCSS, such as choice of the satellite clock, satellite orbital parameters and the constellation size.
Using the Systems Tool Kit simulation software, the authors examined various LNCSS constellation case studies based in elliptical lunar frozen orbit and with a low-grade chip-scale atomic clock.

They evaluated case studies of navigation design considerations including position and timing accuracy, lunar user equivalent ranging error, and dilution of precision. As for case studies of communications design considerations, the authors examined daily data volume, availability and data rate. Finally, they examined smallsat factors including the cost, size, weight and power of the satellite payload.

The paper includes trade-off analysis in satisfying the preliminary design criteria outlined by international space agencies and commercial space companies.

Bhamidipati, Sriramya; Mina, Tara; Sanchez, Alana; Gao, Grace; “A Lunar Navigation and Communication Satellite System with Earth-GPS Time Transfer: Design and Performance Considerations.”

Developing an SDR for Space

A geostationary satellite (GEO) equipped with the satellite-based augmentation system (SBAS) function has a transmitter for GNSS correction signals at the L1 and L5 bands. This transmitter could interfere with the GNSS space service volume (SSV) receiver in the same satellite, so L1 and L5 signals cannot be used for the GEO SBAS satellite. However, the use of GPS L2C signals can be an alternative.

The authors of this paper present the development of a GPS L2C signal generator for the SSV in GEO simulation. They present the simulation process for GEO satellites and the structure of the GPS L2C signal generator.

In this study, a verification through the receiver test with a GNSS software-defined receiver is included to show the possibility of the designed signal simulator. The validation is performed by analyzing the programmable system device, the results of the acquisition, code/carrier tracking, and the C/N0 estimation.

Lee, Hak-beom; Choi, ByeongHyun; Song, Young-Jin; Won, Jong-Hoon; Kwon, Ki-Ho; “Development of GPS L2C Signal Generator for SSV in Geostationary Orbit Simulation.”

Differential Positioning on the Moon

This paper introduces a new concept of delivering the pseudorange correction calculated at a reference station on the lunar surface, as a part of the lunar navigation satellite system (LNSS) navigation message. The concept enables LNSS users to apply differential positioning using pseudorange correction without adding new hardware to their receivers.

The authors propose the differential positioning technique to reduce the signal-in-space range error of LNSS satellites and the coordinate transformation errors from Earth-centered fixed frame to lunar reference frame — the dominant errors in satellite positioning by LNSS.

The proposed reference station is equipped with instruments to externally estimate its own position relative to the lunar reference frame. The user on the lunar surface would then perform differential positioning using the station coordinate and pseudorange correction obtained at the reference station.
In this study, the simulation results using eight elliptical lunar frozen orbit satellites show that the real-mean-squared values for both horizontal and vertical positioning errors with differential correction are reduced to 1/10 of those without differential correction, even at 10 degrees latitude from the reference station at the lunar South Pole.

Akiyama, Kyohei; Murata, Masaya; Kogure, Satoshi; “Differential Positioning Performance on Lunar South Pole Region Using Lunar Navigation Satellite System.”

GEO Precise Orbit Determination

Using GPS in satellites in geostationary (GEO) orbits provides advantages by improving position, velocity and timing data, reducing operating costs and providing autonomous orbit control for station keeping. This paper presents the result of the onboard data evaluation and precise orbit determination of an optical data-relay satellite (ODRS) using GPS L1 C/A code and carrier-phase observations for 74 days.

As a result of precise orbit determination, the authors found that both code- and carrier-phase observations are affected by the ionospheric delay when signals pass through the plasmasphere located above the ionosphere.

Several methods were implemented during this research to reduce the effect of the plasmasphere, including setting a higher cut-off altitude, applying correction sequences generated from orbit determination residuals, and applying a new observation noise model depending on the GPS off-nadir angle. Results show that the correction sequences and the new noise model improve the internal orbit consistency. The authors also found that the orbit bias in radial direction due to negatively biased carrier-phase observations is mitigated from –51 cm to –17 cm by setting a higher cut-off altitude and applying correction sequences.

Matsumoto, Takehiro; Sakamoto, Takushi; Yoshikawa, Kazuhiro; Kasho, Sachiyo; Nakajima, Ayano; Nakamura, Shinichi; “GEO Precise Orbit Determination Using Onboard GPS Carrier Phase Observations of Optical Data Relay Satellite.”

Spencer Cox, the governor of Utah, toured Teal Drones headquarters in Salt Lake City, to learn about Teal’s operations, the company’s impact on the national aerospace and defense industries and opportunities and challenges facing Utah’s local defense industry. The visit was organized by the newly created Utah Aerospace and Defense Association (UADA).

“Teal is deepening its relationship with UADA to help accelerate the rebuilding of America’s defense industrial base, specifically for UAVs,” George Matus, Teal Drone founder and CEO said.

Teal is certified as “Blue UAS,” authorizing the company to provide equipment to the U.S. military. Teal is also one of three UAV manufacturers invited to participate in the U.S. Army’s Short Range Reconnaissance Tranche 2, designed to deliver a portable small uncrewed aerial system that can be used by army platoons for surveillance, reconnaissance duties and improving situational awareness.

UADA was established in 2022 to address challenges associated with innovation, entrepreneurship, workforce development and supply chains for companies in the aerospace and defense industries.

“For far too long, we have ceded the building of UAVs to China and other places,” the governor said. “We are bringing that back and Utah is at the center of that.”

SingularXYZ, a manufacturer of GNSS technology, has launched its DK100 development kit. This multi-functional kit has selectable single-antenna and dual-antenna modules, full constellation tracking and centimeter-level positioning.

The DK100 development kit is a ready-to-use kit designed to simplify integration efforts and increase compatibility with a variety of applications. The kit reserves standard adapter board interfaces to connect different GNSS modules and radio modules for a variety of needs.

The development kit features a 4G module, Wi-Fi, Bluetooth, and Ethernet modules as well as status indicators on a single PCBA.

The DK100 development kit comes with its own web page for configuration. With Ethernet and Wi-Fi access, users can monitor device status and configure working mode and data transmission settings on the page.

The centimeter-level DK100 kit can be integrated in a range of horizontal and vertical applications, such as construction using CORS networks, precision agriculture, construction machinery, smart navigation, monitoring, robotics, unmanned systems and more.

The new DK100 development kits are available now.

On March 23, Shou Zi Chew, CEO of the popular app TikTok, testified before Congress that TikTok does not collect precise location data from its users.

During the hearing, which lasted for more than five hours, Chew assured committee members that the app does not collect nor distribute location data. The terms of service for TikTok also do not mention collection of precise location data.

TikTok is under fire as a bipartisan Senate proposal is aimed at banning the social media app, arguing that it poses cybersecurity risks. The House Committee interrogated Chew regarding the app’s algorithmic feed, policies for young users and —given TikTok’s Chinese ownership — the amount of access the Chinese government has to user data.

ComNav Technology’s K8 series GNSS modules can use the Galileo High Accuracy Service (HAS) precise-point positioning (PPP). The PVT algorithm upgrade to the K8 series module supports Galileo HAS with an accuracy of 20 cm horizontally and 40 cm vertically.

Galileo HAS provides free access to information necessary to estimate accurate positioning using a PPP algorithm in real-time through the Galileo signal E6-B and an internet connection. Galileo HAS Initial Service was declared on January 24, enabling users within the service area to achieve improved positioning performance.

The improved performance capabilities provide a higher level of accuracy for industries such as UAV, autonomous driving, intelligent transportation, agriculture and GIS collection.

in 1999 spurred development of an entirely new type of positioning and location technology. “This project started with the Worchester, Massachusetts, warehouse fire,” said William Stout, program manager for the Department of Homeland Security (DHS) Science and Technology Directorate (S&T). “Six firefighters went in to clear an abandoned warehouse that was on fire to make sure there wasn’t anybody in there, and they got trapped. The team couldn’t find them because they had no idea where they were, and they ended up perishing.

That is what got DHS started with developing a first responder location tracking technology, Stout said.

“Over the years from that point on, we investigated many different technologies. My predecessor referred to most of these as ‘cocktail solutions’ because they would try to merge different types of technologies — for example, GPS and inertial — but none of these panned out.”

Enter Magnetoquasistatics Research

This lack of progress changed in 2012 when they connected with Darmindra Arumugam, group supervisor, senior research technologist and program manager at NASA’s Jet Propulsion Laboratory (JPL). Caltech manages JPL for NASA. In a complete departure from traditional radio signal-based positioning technologies, Arumugam and his team had been researching magnetoquasistatics (M/QS). This is the foundation for the POINTER System.

The system consists of fixed or portable transmitters, for instance, a base unit and controller that can be mounted on a first responder vehicle outside of a building. The first responders carry a small receiver that the base can locate with two characteristics: the field’s strength (for ranging) and its unique pattern (for lack of a better term) for direction (receivers send position info back to the controller via ISM band LoRa). The controller registers and displays the position of each receiver.

Why Magnetic Fields?

Ranging can be done in many modes, Arumugam said, and not all are based on just the amplitude of the propagating wave. With traditional radio signal ranging, to compute a precise position, techniques mostly use multiple sources of signals, for trilateration or multilateration, as GNSS does. However, signals can be perturbed by objects in their path, or experience multipath (signals bouncing off objects), which is a pronounced challenge for indoor environments.

POINTER does not employ radio signals in the fashion of traditional ranging solutions such as GNSS, ultra-wide band (UWB), and various beacon systems for indoor positioning. However, Arumugam said POINTER does generate a radio signal.

“The key difference is that we are detecting the field in a regime where there is no radio propagation mode. Therefore, it is more accurate to refer to this as a quasi-static field, as opposed to a radio propagating wave,” Arumugam said.

Arumugam said Earth’s magnetic field is a good example of this. “It penetrates structures very well, we can measure it 100 kilometers beneath the surface, far above the surface, inside buildings, underwater and so on,” he said. “POINTER uses the kind of the features that you see in Earth’s magnetic field — we are generating quasi-static magnetic fields.

“The term quasi-static highlights the fact that we are trying to keep the physics of the field stationary for all purposes but apply some slow time variation so that it’s really quasi-static to optimize the benefits from both,” Arumugam said. “We get the best of the behaviors of static fields in terms of penetration and non-line-of-sight capability, but also optimize for signal-to-noise by making this a quasi-static signal as opposed to a perfectly static one.”

JPL developed for DHS S&T prototypes that the two organizations tested jointly. Both transmitters and receivers employ an array of three coils, oriented at right angles for x, y and z. The resultant transmitted field carries distinct patterns from these three axes. Distance is detected from field strength, and direction is determined by detecting the pattern of the field relative to the three axes. A key strength of POINTER is that it can achieve ranging and direction from a single base station.

However, Arumugam noted that multiple bases could be beneficial for certain situations.

“The technique as originally developed requires only one transmitter. However, we find that there’s only so much you can get out of a magnetic field, and certain types of structures and materials will perturb that field, causing error.” The second transmitter is not only a backup, but it also helps reduce errors.

POINTER

Geolocation Inc. was spun out from Caltech to license and commercialize POINTER, said Joseph Boystack, executive chairman and co-founder. “We stepped in and executed an exclusive worldwide license for every field of use on this technology in late 2020 from JPL. They had established a proof of concept, and begun testing the technology in the field.”

For the initial commercial version, Balboa Geo made significant improvements over the JPL prototype system. It developed two transmitters that can be deployed on a fixed-mounted basis (buildings, vehicles, ships, etc.) or be portable housed inside a ruggedized, military specification (MIL-STD) case, with a built-in dual antenna GNSS receiver (to position and orient the transmitter).

“If you have an incident involving first responders, military or industrial applications, these remotely configured transmitters can be quickly and easily deployed,” Boystack said. “Also very important, because it only needs to depend on the field generated by the transmitter, we’re not dependent upon other large, fixed infrastructure such as satellites, towers or beacons, and can work in degraded environments where most other position, navigation and timing techniques fail.”

The self-contained receivers are only about the size of a smartphone. The orientation of the receiver is important to determine the “xyz” axis relative to the generated field, thus providing highly accurate three-dimensional position and navigation data. For instance, Balboa Geo’s receiver can be clipped to a first responder’s belt, harness, or personal protective equipment. Similarly, for fixed assets or moving assets such as warehouse systems or robotics, the orientation would be known.

The POINTER system will generate real-time data that can be easily visualized at the job site or event by the incident commander or manager on a laptop or a tablet. The data is interoperable and may be ingested in third-party software applications.

This version meets DHS STS’s original expectations, and subsequent versions will build on it. “S&T relies on experienced emergency response and preparedness professionals to guide our research and development. The First Responder Resource Group is made up of hundreds of state and local volunteers,” Stout said. “We initially looked at tracking firefighters in some of the most common scenarios: two-story house fires.”

While POINTER technology has the potential for much longer ranges and precisions, the current version, Arumugam said, certainly meets the specifications for this initial application. “The current systems can operate up to about 75 meters in range from the transmitter. So, if a transmitter is placed about 10 meters outside the building, say on the fire truck, you can penetrate up to about 65 meters inside the structure. That covers many one, two, maybe three-story structures. Position accuracies can be one meter or less. In principle, you could get to a centimeter, but that’s not required for this technology to be the lifesaver it presently needs to be.”

JPL continues research and development to extend range and increase precision to enable DHS S&T to deploy this technology to ever broader safety-of-life applications where legacy technologies fall short or are completely impractical. Balboa Geo is conducting field and lab tests for many more applications across multiple industries including energy, construction, maritime, mining, the internet of things and more.

Sharper Shape has used SimActive software’s distributed processing capabilities to complete utility corridor base maps in Montreal, Canada. In 2022, more than eight million images were collected in SimActive’s Correlator3D software to generate orthomosaics and colorized point clouds.

Correlator3D, hosted on an Amazon cloud environment, enabled quick processing of thousands of images per day over a network of virtual machines. The resulting map products covered more than 34,000 miles of utility corridor and were imported into Sharper Shape’s artificial intelligence (AI) tools to extract infrastructure information.

“The quantity of data that we capture to feed our AI tools for utility infrastructure deliverables is incredible and comes from various geographical locations at the same time,” said Petri Rauhakallio, vice president of business development at Sharper Shape. “Correlator3D allows our teams to easily import and process massive amounts of imagery for use in our digital twin production.”

Adtran and Satelles, a provider of secure time and location technology using low-Earth-orbit (LEO) satellites, have partnered to offer operators of critical infrastructure a timing network device with satellite, time and location (STL) technology. The partnership aims to provide an alternative to GNSS by integrating STL technology from Satelles into Adtran’s Oscilloquartz network synchronization products.

Through its partnership with Satelles, Adtran’s Oscilloquartz division will incorporate STL into its end-to-end timing toolkit. The companies will also integrate STL into its grandmaster clocks to develop miniature M.2 form factor STL receiver modules for third-party product integration.

With the ability to deliver precise position, navigation and timing (PNT) service in GNSS-denied applications, STL is suitable for mobile operators, power utility companies, government, scientific research and more. STL technology also offers accurate, secure and augmented Iridium LEO-based PNT services for indoor applications and as backup for GNSS outdoors.

Eos Positioning Systems has released its Arrow Gold+ GNSS receiver, which supports the Galileo high-accuracy service (HAS). Arrow Gold+ enables users to achieve better than 20 cm accuracy with 95% confidence using Galileo HAS.

The Arrow Gold+ is one of the first high-accuracy GNSS receivers that supports Galileo HAS and is designed specifically for the geographic information systems market. Additional signal support for Arrow Gold+ includes: the concurrent use of the BeiDou B3 and GPS L5 signals as well as GLONASS, BeiDou, QZSS and IRNSS signals.

Galileo HAS is a differential correction service from the European Space Agency and European Union Agency for the Space Programme. The service became available on January 24, and it is the first global differential correction service to provide sub-meter accuracy to compatible GNSS receivers anywhere in the world.

For more information on the Arrow Gold+ click here.

Some airlines and military aircraft, including the Australian commercial airline Qantas, are receiving radio interference and GPS jamming from alleged Chinese warships in the Asia Pacific, report Australia Aviation and The Guardian.

The International Federation of Air Line Pilots’ Associations (IFALPA) released a statement acknowledging the reports of interference and recommended that pilots carry on, not respond to the warships and report all incidents to air traffic control.

“IFALPA has been made aware of some airlines and military aircraft being called over 121.50 or 123.45 by military warships in the Pacific region, notably South China Sea, Philippine Sea, East of Indian Ocean. In some cases, the flights were provided vectors to avoid the airspace over the warship. We have reason to believe there may be interferences to GNSS and RADALT as well,” the statement noted.

Further recommendations from IFALPA include notifying company dispatchers of the attempted contact and completing an ASAP report or other company safety report for non-ATC communication or GNSS interference.