On 8/12/18 6:36 PM, David I. Emery wrote:
On Sun, Aug 12, 2018 at 07:48:52PM -0400, Bob kb8tq wrote:
Hi
Well???. there???s also the solar flare that vaporizes the planet earth :)
A flare big enough to take out all the sat systems would disrupt a lot more
than just navigation.
But It is much more likely that orbits would be less accurately
known for a while due to atmospheric heating and increased drag and
maybe also due to disturbances in satellite orientation and power and
thermal status during the event that could both change drag and perhaps
even induce slight impulses if gas jets or similar means were required
to recover the bird and make it stable again. And the power and
thermal perturbations in emergency mode shutdown configurations might
well impact the on board clock performance and accuracy (even maybe just
from the extra radiation as the magnetopause moved inside the satellite
orbits in an extreme event).
GPS is up high enough that aerodrag isn't really a problem - if you're
above 1500km, it's negligible, and they're up at 20,000km.
Solar wind pressure will push them around a bit, but not much. I would
think that if you did nothing, they'll be there for a very, very long time.
Their orbit is actually a quite high radiation zone (traversing the
radiation belts as they pass through the polar region), compared to GEO.
So the GPS satellites are pretty robust to this kind of thing.
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