| sat_alight@yahoo.com 2006-09-30, 12:33 pm |
| I agree with Tom. Although I think it was good to publish their paper,
it's not a "armageddon" sort of thing for GPS. The press has gone a
little over-the-top on it.
And admittedly he says their data from the '03 storm doesn't
differeniate between right or left HCP. GPS is RHCP so any LHCP
activity has no effect on it.
>
> Sam,
>
> The extrapolation of a 3 to 6 dB C/No dip for a short period this past
> solar peak to "all receivers on the sunny side of the earth will fail
> for hours" is bad pseudo science at its worst. It would have been
> more honest for them to have said that the 3 to 6 dB dip could happen
> more often than once or twice every 11 years or that the dip could get
> a couple dB deeper during the next cycle. But extrapolating predicted
> (and somewhat speculative) estimates that say that the next solar peak
> may be a little more active to there is going to be armageddon level
> radio wave flares is bunk.
>
> In addition, the statement about life-critical systems, implying a
> direct hazard to life impact is not correct and demonstrates that the
> authors are completely unaware of the hazard analyses associated with
> aviation navigation. The critical safety aspect of WAAS is that the
> system will not direct airplanes to fly into the ground. The hazard
> that a WAAS approach becomes unavailable as it is being flown is a
> "minor" hazard that would result in the execution of a missed approach
> procedure if the weather is below the visual minimums. If weather is
> below minimums and there isn't a non-GPS approach at that airport, the
> pilot goes to his alternate airport. Not really any different than if
> the weather falls below the precision approach minimums.
>
> However, the author's point that GPS is vulnerable to interference and
> solar storm effects does reinforce the recommendations that; a subset
> of the existing ground based navigation aids need to be retained as a
> backup, the transmit power on the GPS satellites should be increased,
> and the number of satellites should be increased to provide a more
> robust system.
>
>
> Tom
|