[ntp:questions] NTP architecture recommendation

Joseph Gwinn joegwinn at comcast.net
Sun Aug 19 21:28:36 UTC 2007


In article <46C89C09.1040902 at comcast.net>,
 "Richard B. Gilbert" <rgilbert88 at comcast.net> wrote:

> David J Taylor wrote:
> > Richard B. Gilbert wrote:
> > []
> > 
> >>I don't think that a 14 channel receiver would be useful!  There
> >>simply are not that many satellites!  The last I knew, there were 27
> >>NavStar (GPS) satellites in orbit.  Of these, about seven are usually
> >>above the horizon at any one time.
> > 
> > 
> > Richard,
> > 
> > There can be more than that - here's an example with 13 visible.
> > 
> >   http://www.david-taylor.myby.co.uk/software/wxtrack-extras.htm
> > 
> > According to this source, there are 31 active satellites:
> > 
> >   http://celestrak.com/NORAD/elements/gps-ops.txt
> > 
> > More in orbit, I expect, now dead.
> > What do they do with decommissioned GPS satellites?
> > 
> > Cheers,
> > David 
> > 
> > 
> 
> I suspect there's not much they can do with decommissioned GPS satellites!
> 
> You could probably launch 27 GPS satellites for the cost of one manned 
> mission to retrieve/repair one.
> 
> If you wait long enough, they will come down by themselves!  It may take 
> a few hundred years. . . .

If I recall, they have a deorbiting system, which is a rocket that fires 
against their orbital motion, causing them to fall out of orbit rather 
more quickly than that.  Of course, if the satellite has completely 
failed, the deorbit system won't be listening for commands, but usually 
things won't get that bad suddenly.

Joe Gwinn




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