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    Re: Star Trackers Harden Ground Targeting Systems from GPS Spoofing
    From: Frank Reed
    Date: 2014 Jan 10, 14:04 -0800

    From the press release:
    "Trex Enterprises’ is developing a multi-aperture stellar tracker able to detect stars during daylight. Trex has developed proprietary automated star pattern recognition algorithms. Working with the U.S. Navy, Trex has developed and demonstrated the Daytime Stellar Imager, an infrared sensor capable of seeing stars in daylight and at night, thus being able to create an alternative navigating system. Such system could be used on naval surface vessels and aircraft, independent of global positioning systems (GPS) or Inertial Guidance Systems (INS). The system can deliver precision azimuth reference, for precision pointing at sea and on battlefield. Trex Enterprises developed the automated the star detection capability and pattern recognition algorithm. The system can detect a 6.3 magnitude star at daytime, at sea level."

    I'm not surprised they can detect first and second magnitude stars. I'm impressed that they can get as deep as magnitude 6.3. Given that, the "multi-apertures" can be presumably be pointed in fixed directions relative to each other. For example, you could have one pointing "up" and three others evenly spaced in azimuth angled sixty degrees away from the "up" sensor. Each could detect dozens of stars and then it's just pattern-matching to identify the stars and convert that to orientation data. There's no clue yet in any of the articles how this particular system establishes a vertical. Perhaps it's semi-inertial, or maybe it's by refraction (which would require a few more sensors aimed at low altitudes).

    By the way, the astro-compass capability of a system like this is genuinely unique. Orientation is one problem that astronomy solves far better than any other system.

    A cloudy day is still a show-stopper!

    -FER

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