Genevieve Poblano / Digital Trends
In the past five years, SpaceX has embarked on a mind-boggling project: the Starlink satellite constellation. The big plan is to put more than 12,000 satellites (or more) into low-earth orbit and place them in an undulating, grid-like array that will allow SpaceX to deliver high-speed broadband internet to every corner of the planet.
To date, SpaceX has launched nearly 900 Starlink satellites into orbit and has even launched beta access to its fledgling satellite internet service. Internet access may not be the only trick this mega-constellation has up its sleeve, however. Researchers believe it could also be used for a secondary mission: creating a next-generation navigation system that could replace GPS.
Peter Iannucci and Todd Humphreys of the Radionavigation Laboratory at the University of Texas at Austin looked into how this could be done and recently published an article on their research. Iannucci explains to Digital Trends that setting up a navigation system from scratch in low-earth orbit would be too costly, but using the Starlink satellites would be affordable.
“We’re talking about a system where the positioning mission doesn’t have to bear the financial burden of supporting tens of thousands of satellites because they have one main mission, which is the Internet service,” says Ianucci. “Everyone must have an internet service.”
Because these satellites are in near-earth orbit (about 350 miles from the surface of the earth) and therefore closer to the planet than traditional GPS satellites (which orbit about 12,000 miles away), they could theoretically provide a stronger signal for navigation as GPS can generate. This would help prevent the signal from being intentionally or unintentionally disturbed, which is relatively easy to do with conventional GPS. According to Ianucci, GPS signals are accidentally jammed all the time.
“GPS jamming is easily accessible even to amateurs – even casual actors can intentionally or unintentionally jam GPS,” says Ianucci. “These [low-Earth orbit] Signals could be roughly 400,000 times more immune to interference. That’s big.”
According to Ianucci, these small satellites in near-earth orbit only need a software update to achieve improved navigation. These satellites already have a rough idea of where they are, which is necessary to prevent a collision, but Ianucci says the software update will do it so they’ll know where they are much more accurately.
“We would be pushing for software upgrades and possibly hardware upgrades that refine these positioning estimates beyond what is required for safe orbit operation,” says Ianucci.
One way to do this is to have the satellites popped by the GPS satellites higher in the atmosphere to help them find their location. Once the software is set up, receivers on the ground can pick up signals that these satellites are constantly sending and use them for navigation.
Build a better GPS
Mark Psiaki, a professor in the Department of Aerospace and Ocean Engineering at Virginia Tech, told Digital Trends that this navigation system would not only help us avoid interference, it would also be more accurate.
“One of the advantages of Earth orbit is just that [the satellites there] move so fast. They just scream across the sky very quickly, ”says Psiaki.
He says that if you receive signals from dozens of fast-moving satellites at the same time, you can get a more accurate picture of where you are than if you receive signals from a small number of slow-moving satellites. This will be important as we bring autonomous cars and delivery drones into the world.
“There’s a push for something called PPP or precise point positioning. Right now, simple vanilla GPS and the others have an accuracy of the order of a meter or a few meters if everything goes right, ”says Psiaki. “That’s not enough to keep a car in one lane on a freeway. You could go on the next lane or on your shoulder. If you could have precise point positioning, now we’re talking 10 centimeters. “
According to Psiaki, PPP can be made compatible with our current GPS system, but it is very complicated and takes a long time. If we were to use low-earth orbit satellites for this it would be much faster and very reliable. He says we could cut the time between turning on the receiver and running PPP from about 20 minutes to maybe a minute.
Not only would we get a stronger signal from these satellites, but we would also be able to get autonomous cars on the road faster and make sure our delivery drones don’t collide with each other or against other objects. All these researchers need is someone like Elon Musk to agree to make some software changes.
“If we can show them that the investment they are already making is paying off in these unexpected secondary ways, it will be a win for them and a huge win for us in the navigation community,” says Iannucci.