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    Re: New inovation in astro navigation?
    From: Douglas Denny
    Date: 2010 Aug 3, 04:36 -0700

    Jim Wilson says:
    "Natural catastrophes occur not only on earth but in space as well, and a gigantic solar flare is one of those. None has occurred since we've been monitoring them, but they are lurking. And a single one could knock out all satellites!"
    -------------

    If there is a solar flare _that_ big it would have serious repercussions on all communications systems and on Earth too. Satellites are protected against EMP and solar flares. They are designed to resist EMP of upper atmospheric nuclear explosions. The solar flares are more likely to disrupt the ionosphere to give large variability of propagation affecting position rather than killing the satellites.

    More likely in probability terms is 'selective availability' being a problem: It is entirely possible for the Americans to have the satellites switch off as they pass over selected parts of the globe, or degrade the signals (as they used to do) to reduce positional accuracy, or even move the parameters entirely for position, which would make good sense if you knew a missile was coming your way which was using GPS in a wartime scenario.
    It is for this reason that the Europeans want their own satellite navigation system independent of GPS with 'Galilleo', and the Russians keep 'Glonas'. Even other nations want their own independent systems despite the Americans declaring GPS would be inviolate from now on.

    I think there should be an internationally controlled satellite positional system where every country contributes to an international funding for it through the United Nations, but control would be by the UN. This would remove the duplication and huge costs for each system.

    However .. I agree with you actually about the very valid point of having an independent method available to find position; (as the governments want too). There is no disagreement there. In my opinion it would be foolish not to.
    I personally would never venture offshore without the equipment for astro-navigation at my fingertips.

    Douglas Denny.
    Chichester. England.
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