Humans have always navigated using the stars, and now NASA has taken that concept to a new level of precision. An x-ray telescope onboard the International Space Station demonstrated a navigation system based entirely on detecting the periodic x-ray emissions of certain neutron stars (pulsars). Keith Gendreau of the NASA Goddard Space Flight Center reported on the results at the American Astronomical Society meeting in Washington, DC, this month. The navigation system, called the Station Explorer for X-ray Timing and Navigation Technology, or SEXTANT, was able to locate the spacecraft to within 10 km. This level of accuracy is comparable with traditional navigation techniques for space probes in the outer Solar System, where signals from Earth’s radio telescopes are weak.
All US interplanetary probes rely on NASA’s Deep Space Network (DSN) of radio telescopes for navigation, as it can determine a probe’s distance from Earth with centimeter-scale accuracy. But the DSN is much less accurate for lateral distances, and its accuracy decreases with the distance from Earth. NASA would also like to reduce the heavy usage of the DSN and to develop an independent, autonomous navigation system that would provide redundancy, especially for future missions that may include humans.
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