[time-nuts] Timing Distribution in Mountainous Terrain

jimlux jimlux at earthlink.net
Fri Sep 10 14:02:10 UTC 2010

Peter Monta wrote:
>> Aren't pulsars a reliable accurate time source or do they not provide the 30nS over ten days accuracy?
> By using them in common view, though, any absolute error would drop
> out.  I'm not sure pulsar pulses are fast enough to do discrimination
> at 30 ns time scales, though.  VLBI with broadband sources (quasars)
> would be fine here, but large amounts of data would need to be
> exchanged, and the sources are weak, requiring large antennas.
> Satellite laser ranging using LAGEOS and friends?  But the original
> poster said no satellites (not even passive rocks in MEO?), and
> weather is a problem.

Hmm.. here's an idea
look for the 217 MHz signals reflected from LEO satellites and 
NAVSPASUR.. big illuminating fence, fairly easily detectable signals, 
LEO satellite so ionosphere isn't a big deal.  You get many satellites 
per hour crossing the fence.

Actually, if any satellites are available, how about using TV signals 
from GEO relays?  (or is the presumption that everything above 50,000 ft 
MSL has been wiped out?) Some folks at  JPL have used such signals to do 
microwave holography on big antennas (big signal, essentially plane 
wavefront, etc.)

For that matter, LEO satellites aren't that far away, and your Lband 
interrogator for the transponder could probably light them up and 
reflect some power back.  You'd have to run the radar equation and see 
how much power you get back... I have no idea about the RCS of a LEO 
satellite, but I'll bet its "many" square meters  (if you count ISS as a 
candidate.. thousands of square meters RCS)  ISS passes over several 
times a day, and while its orbit isn't particularly well known or 
controlled (at least not to a scale of meters), it might be good enough 
for you.

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