In a technology first, a team of NASA engineers has demonstrated fully autonomous X-ray navigation in space.
(NICER mission over view video)
The demonstration, which the team carried out with an experiment called Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT, showed that millisecond pulsars could be used to accurately determine the location of an object moving at thousands of miles per hour in space — similar to how the Global Positioning System, widely known as GPS, provides positioning, navigation, and timing services to users on Earth with its constellation of 24 operating satellites.
“This demonstration is a breakthrough for future deep space exploration,” said SEXTANT Project Manager Jason Mitchell, an aerospace technologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “As the first to demonstrate X-ray navigation fully autonomously and in real-time in space, we are now leading the way.”
The SEXTANT technology demonstration, which NASA’s Space Technology Mission Directorate had funded under its Game Changing Program, took advantage of the 52 X-ray telescopes and silicon-drift detectors that make up NASA’s Neutron-star Interior Composition Explorer, or NICER. Since its successful deployment as an external attached payload on the International Space Station in June, it has trained its optics on some of the most unusual objects in the universe.
In the SEXTANT demonstration that occurred over the Veteran’s Day holiday in 2017, the SEXTANT team selected four millisecond pulsar targets — J0218+4232, B1821-24, J0030+0451, and J0437-4715 — and directed NICER to orient itself so it could detect X-rays within their sweeping beams of light. The millisecond pulsars used by SEXTANT are so stable that their pulse arrival times can be predicted to accuracies of microseconds for years into the future.
Science fiction authors put forward the idea of a using regularly pulsating stars quite early; check out the space beacon from George O. Smith's 1952 story Troubled Star, which uses variable stars.
In his 1959 short story The Repairman, Harry Harrison points out that a hyperspace jump requires at least four beacons for a good fix; see the quote in hyperspace beacon.