Distances to different orbits can be hard to understand. For example, the ISS sits around 400 kilometers from Earth, whereas some satellites, such as Starlink, orbit at about 550 km. Often that is intentional, as objects in those orbits will eventually degrade their orbit and burn up in Earth’s atmosphere. However, many systems orbit a few orders of magnitude higher – such as the Galileo satellites that make up the backbone of the European Union’s satellite navigation network. At an orbit of around 23000 km, it has some advantages over lower-hanging satellites but also plenty of disadvantages too. Now, the EU was to eliminate some of those disadvantages by releasing a whole new set of lower-orbiting satnav satellites.
Some of the advantages are pretty apparent. While Galileo and similar GNSS systems can reach almost everywhere on the planet – they aren’t particularly accurate. A few meters one way or another isn’t too big of a deal when you’re simply dealing with cell phone navigation apps. But for applications such as smart cities or even genuinely driverless cars, the precision has to be on the order of centimeters, not meters, to be effective.
GNSS satellites have trouble providing that accuracy, in large part because they are so far away. Other orbits that bring satellites closer to the ground could allow for more accurate pinpointing of receiving devices and allow for uses in a broader range of applications.
Another disadvantage of large-scale GNSS satellites is their operating frequency. It uses the L-band, which is between 1-2 GHz on the electromagnetic spectrum. However, these bands aren’t helpful in some situations, for example, in concrete buildings.
For example, there are plenty of scenarios in the industrial internet of things where a robot would need to know its position inside a concrete building. So having a set of smaller satellites with a broader range of operating frequencies could allow those situations to still get accurate positioning data from a lower-hanging subset of satellites.
What’s more, satellite technologies have advanced a great deal lately, and having the infrastructure of Galileo and other navigational constellations support these new constellations would even further increase their technological advantages. For example, any new satellites wouldn’t have to have expensive and bulky atomic clocks on them, as they can simply receive an accurate timestamp from the geosynchronous satellites orbiting above them, the same as any other GPS receiver would.
Eliminating some of those redundancies, and making specialized equipment for specific frequencies and applications, would allow the lower orbiting satellite systems to clock in at only about 1/10th the size of a Galileo, which weighs a hefty 700 kg. As launch costs are a significant limitation for the commercial adoption of many of these technologies, lowering a satellite’s launch weight is one of the primary goals of any design team.
Commercial applicability seems to be one of the core focal points of the effort to develop these novel systems. The EU is already a leader in satellite system development and obviously wants to remain so. With this new effort to get a constellation of improved satnav satellites up into orbit, the block, and ESA, its space agency, hopes to keep itself at the forefront of this fast-growing field of commercial space.
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Depiction of a world-covering satellite system.
Credit – ESA – Science Office