This paper is based on findings from an analysis performed for EUSPA.
What LEO-PNT stands for
LEO-PNT means Low Earth Orbit Position Navigation Timing and encompasses all satellite networks in LEO orbit (typically 500-1500km altitude) that are used to provide PNT services. As a reminder, GPS and Galileo are MEO PNT, orbiting at around 20000km of altitude.
While Galileo and GPS are everywhere (cars, smartphones…), this technology has well known limitations: weak signal, large power consumption of receivers, limited accuracy, easy to jam or spoof and reduced performance in cities, in dense forests or even under rainfalls…
This has led to many complementary solutions and LEO PNT is the latest one. LEO PNT consists in launching hundreds of satellites in a closer to earth orbit. These satellites broadcast signals similar to GPS and in nearby frequency bands. The method of calculation remains the same, making it relatively simple to design adequate receivers. Some LEO PNT architectures use GNSS signals as a reference, thus not needing atomic clocks, which reduces the cost ot the satellites. This is important as a LEO PNT constellation requires many more satellites than GNSS as satellites are closer to erath, typically hundreds vs 20/30 for GNSS.
Benefits of LEO PNT
The promised benefits of LEO PNT are numerous:
- Better accuracy, in the dm range, thanks to a large number of satellites which allows to have more satellites simultaneously visible from a receiver
- Stronger signal that is difficult to jam or spoof increasing the resistance of the service
- Better performance in constrained environments such as cities
- Lower power consumption on the receiver side
All these benefits pave the way for the adoption by many use cases like IoT, automotive, drones, agritech, etc… that need more than current GNSS. Given these opportunities, many LEO PNT projects have emerged .
Two commercial projects currently lead the pack.
Xona is a US start-up that plans to launch 300 satellites to provide commercial LEO PNT. A demo sat was launched in 2022 and apparently validated the concept in may 2023 . Xona plans to address essentialy the automotive market for autonomous and connected vehicles.
Geespace is a subsidiary of Geely, the Chinese car manufacturer. 9 satellites were launched in 2022 with little details available. However, the constellation should count ultimately more than 200 satellites providing both car connectivity and centimeter level position accuracy, And yes, the target market is automotive as well, starting probably with Geely cars…
Other projects are probably being worked on, for example Porsche had announced in the past its own LEO-PNT constellation, but no information has been made available. Centispace in China and Thrustpoint in the USA have also announced projects.
On the technology side, ESA launched its futurenav initiative that will lead to demonstrators flying starting in 2026.
So LEO PNT or not LEO PNT?
While the technology of LEO PNT seems promising, no project has a clear path to market yet as the large number of satellites needed requires a very large investment. This makes the business case uncertain as the large majority of GNSS users are not paying anything today for the service – and probably have no intention to pay anything… Thus new business models will need to be proposed to make the tab acceptable…
At the same time, a lot of R&D has been done on using signals from existing constellations (Starlink, OneWEB or even Iridium, Globalstar) to complement and improve GNSS. This will have similar benefits as LEO PNT: better accuracy and integrity thanks to frequency and geormetrical diversity. And it does not require to launch any additional satellites, which makes that most economical.
In the end, the solution to improve GNSS will probably come from hybridization of technologies, using a variety of means, be it space or ground based. One thing remains certain: we are so used to our satellite navigation devices that we will use them more and more and will ask always better accuracy, faster TTF and working in all conditions…