NASA’s New Interplanetary GPS Is More Old-School Than It Sounds

As Jason Mitchell, an engineer on the project as NASA’s Goddard Space Flight centre, explained to IEEE Spectrum, the new system “will allow our descendants to accurately and autonomously navigate not only throughout the solar system but beyond it as well.” Mitchell explained that the further we travel from Earth, the less sense our current system makes. “Maybe in the future, when we’re exploring space regularly, we won’t need to rely on a gigantic, Earth-based infrastructure,” he said.

If astronauts aren’t relying on technology back home, though, then where do they turn? The stars of course. That’s right, just like swashbucklers sailing the Seven Seas and nomads wandering the desert, this new super advanced system draws on the same basic principles of navigation that have been in use for millenia. There is a futuristic component that sets it apart from the Antikythera mechanism, though, and it involves pulsars.

Traditionally, space navigation depends on radio waves being beamed from Earth out to the space craft. This is time-consuming since radio waves only travel so fast, and it’s also limiting since the craft is almost literally tethered to Earth by the signal. The new system, however, is fully autonomous. Rather than relay messages themselves, the space crews will look to pulsars, zombie stars that blink at regular intervals, to serve as points of reference. The pulsars work a lot like lighthouses, the pretty things in Maine and elsewhere that have long kept ships from running into shore in areas of low visibility.

It wouldn’t be quite right to think of pulsars as blinking lights that astronauts could spot outside of portholes. (See above for the sort of cyberpunk effect that is a blinking pulsar.) But again, this is the future, and some futuristic methods are necessarily. IEEE Spectrum explains the workflow:

A craft heading into space would carry a detector that, similarly to a GPS receiver, would accept X-rays from multiple pulsars and use them to resolve its location. These detectors — called XNAV receivers — would sense X-ray photons in the pulsars’ sweeping light. For each of four or more pulsars, the receiver would collect multiple X-ray photons and build a “light curve.” The peak in each light curve would be tagged with a precise time. The timing of these peaks with respect to one another would change as you traveled through the solar system, drawing nearer to the source of some and farther from others. From this pattern of peaks, the spacecraft could calculate its position.

Got that? You can compare the system to lighthouses or you could compare it to the sonar navigation systems on submarines. Either way, it’s pretty amazing. [IEEE Spectrum via PopSci]