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    Re: Star Trackers Harden Ground Targeting Systems from GPS Spoofing
    From: Robert Wyatt
    Date: 2014 Jan 10, 16:55 -0600

    Fascinating technology! Possibly well-suited to finding transient
    "stars" (meaning previously unidentified asteroids) given an appropriate
    observation location, such as a small satellite.
    --rtw
    
    Frank Reed wrote:
    >  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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