Scientists demonstrate first space navigation on ISS using pulsars


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The stars are ours! Scientists using an x-ray telescope installed on ISS have demonstrated it is possible to pinpoint the location of a spaceship and thus navigate through space using pulsars.

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.

During the two-day experiment, the payload generated 78 measurements to get timing data, which the SEXTANT experiment fed into its specially developed onboard algorithms to autonomously stitch together a navigational solution that revealed the location of NICER in its orbit around Earth as a space station payload. The team compared that solution against location data gathered by NICER’s onboard GPS receiver. “For the onboard measurements to be meaningful, we needed to develop a model that predicted the arrival times using ground-based observations provided by our collaborators at radio telescopes around the world,” said Paul Ray, a SEXTANT co-investigator with the U. S. Naval Research Laboratory. “The difference between the measurement and the model prediction is what gives us our navigation information.”

The goal was to demonstrate that the system could locate NICER within a 10-mile radius as the space station sped around Earth at slightly more than 17,500 mph. Within eight hours of starting the experiment on November 9, the system converged on a location within the targeted range of 10 miles and remained well below that threshold for the rest of the experiment, Mitchell said. In fact, “a good portion” of the data showed positions that were accurate to within three miles. “This was much faster than the two weeks we allotted for the experiment,” said SEXTANT System Architect Luke Winternitz, who works at Goddard. “We had indications that our system would work, but the weekend experiment finally demonstrated the system’s ability to work autonomously.”

I think everyone who is interested in interstellar space travel has assumed since the discovery of the first pulsars that they would end up serving as the future north star for interstellar travelers. This experiment shows us how it will be done.

Well read science fiction fans should recognized the literary reference in the tagline.

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3 comments

  • Localfluff

    Once upon a time watchmakers were very carefully designing and assembling their cogwheels and springs. Now they instead trust some theory, based on point sources, of these weird neutron worlds that have such deep gravity wells that one would see both poles at the same time because the concept of hemisphere doesn’t rhyme with relativity effects at the extreme. Funny thing is that it works perfectly. Since astrology went out of fashion in the 17th century, I doubt any astronomer for several generations would’ve suggested anything like this being possible. Too strange, too much like astrology.

  • Jeff

    The Stars are Ours by Andre Norton. I have the red hardback library binding.
    Geo. A. Flohr Co. Cincinnati Ohio.
    The story is very dystopian and sad.

  • Jeff: I do not agree about this book. In fact, it was the first sci-fi book I ever read, and as a child I found it quite inspiring. From the end:

    Frontiers of any type, physical or mental, are but a challenge to our breed. Nothing can stop the questing of man, not even Man. If we will it, not only the wonders of space, but the very stars are ours!

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