NASA Is Reportedly Planning to Bring GPS Service to the Moon

GPS has become so integral a part in our lives most of us probably cannot imagine our daily lives without it. But plotting a 300 miles drive from St. Louis to Chicago is far more different from plotting a course for an autonomous lunar rover trying to get from Mare Serenitatis to Mare Tranquilitatis. But now, if NASA succeeds, drawing a path on the Moon won't be any more difficult than using SatNav on Earth.

Location Service In Space

It is not easy estimating your position on a different celestial body. Fortunate enough, stars’ position is static. So with specialized equipment like star trackers, sun trackers, and accelerometers, as well as taking into account some unique landmarks in the surrounding, a rover can triangulate its position pretty accurately. But that’s too complicated, though, we didn’t have to go through all that on Earth: Just tap a button on a GPS receiver and you’d have your location accurate to a few meters.

Instead of using actual stars as a guide, we created our own constellation of fixed, artificial stars in the form of GPS satellites in geosynchronous orbit. These satellites constantly emit unique signals that can be caught up by a receiver, sampled individually, and automatically locate the relative position of the user on Earth based on these signals.

Needless to say, researchers would love to have this capability on the Moon. But the distance - a whopping quarter of a million miles - can make thing pretty difficult for a system that requires accurate timing down to the nano-seconds and signal measurement. However, tech-wise, there is nothing that’s stopping us from doing that. We have all of the technical knowledge and resources needed to set up a fully functional Moon-based GPS system. In fact, back in 2015, NASA has done a similar project with the Magnetospheric Multi-scale Mission (MMS) that covered roughly half of the quarter million miles distance before.

Commenting on the matter, Luke Winternitz - the system architect of the MMS program - shared that NASA has been trying to push high-altitude GPS tech for years. And the next step is to bring the system to the Moon.

The Complications

But if you bring a commercial grade or your phone to the Moon and try to get a GPS signal, it won’t work of course. Earth-based GPS devices are calibrated to receive only GPS signals from known orbiting satellites overhead within a certain range of distance in-between. By calculating the time it takes for the GPS signals to arrive from three to more satellites, the receiver and the satellites can work together to pinpoint you on a map through a process called trilateration.

Since timing is so important, every mili-seconds missing can affect the accuracy. From orbit, the satellites only need a fraction of a second to reach the ground. Meanwhile, from the Moon, it takes a whole second and a half. There will have to be receivers specifically tuned to work on the Moon for the system to work.

NavCube And the Future

That’s been the aim of a research team at NASA’s Goddard Space Flight Centre: A new navigation computer that utilises a high-gain antenna, an atomic clock for precise timing, a couple of improvements learned from earlier NavCube GPS missions and improved version of Earth-based GPS receivers.

The primary goal is to take advantage of the available GPS constellation surrounding Earth to navigate instead of having to use specialised measurement systems. This can drastically cut back bandwidth and power usage, freeing up the systems on the rover for more scientific tasks or high-priority transmissions.

The team hopes to complete the development of the project by the end of the year and implements it on a future lunar mission. However, with renewed interests of returning to the Moon recently, it seems like there would be no shortage of missions from here on out.