spaceSpace and Physics

Cosmic Positioning System Could Help Interplanetary Spacecraft Find Their Way


Jonathan O'Callaghan

Senior Staff Writer


When embarking on a mission to another planet, it’s always a good idea to know where you are. Thanks to a new technology, spacecraft could soon be able to do this all by themselves, by tracking their position using a cosmic positioning system.

On Earth we can track our location using the global positioning system (GPS) satellites. This doesn’t work when you’re traveling through space, however, so you need another way to track spacecraft.


Currently, we do this by monitoring their radio signals from Earth and triangulating their position. But this new idea is based on using pulsars, rapidly rotating neutron stars, to determine a spacecraft’s location.

At the American Astronomical Society (AAS) meeting in Washington this week, Jason Mitchell from NASA Goddard described how the new technique, which uses X-rays, means spacecraft wouldn’t need Earth’s help at all.

The team used a detector on the International Space Station called the Neutron-star Interior Composition Explorer (NICER) to perform a demonstration of their technology. Called the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT), the project took place in November 2017.

“This demonstration is a breakthrough for future deep space exploration,” Mitchell said.

NICER was installed outside the ISS in June 2017. NASA

The team used NICER to record X-rays from four millisecond pulsars – those that rotate at the incredibly rapid pace of less than 10 milliseconds. Millisecond pulsars are useful because they pulse with an exceedingly regular beat, one that can be extrapolated for years into the future.

NICER picked up 78 readings of X-rays from these pulsars over the two days of the experiment. Using these measurements, the researchers were then able to pinpoint the location of NICER to a range of about 16 kilometers (10 miles), and down to about 5 kilometers (3 miles) at times.

While this might not sound that accurate, it’s good enough to use when traveling through space. It’s hoped the technology could be refined to track a spacecraft within a few hundred feet, which would be fine for interplanetary travel and very useful.

“If an interplanetary mission to the moons of Jupiter or Saturn were equipped with such a navigational device, for example, it would be able to calculate its location autonomously, for long periods of time without communicating with Earth,” NASA noted in a statement.


Using pulsars to track position is not entirely new. Famously the twin Voyager spacecraft, currently making their way out of the Solar System, each have a golden record that contains a pulsar map showing any prospective aliens how to find Earth.

For autonomous spacecraft navigation, though, it’s a bit of a new idea. So if you find yourself on a mission to a distant planet in the future, you might just have a cosmic positioning system like this to thank for helping you find your way.

The Golden Records on the Voyager spacecraft include a pulsar map to find Earth. NASA


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