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Re: AO-40 in one piece



>If it's in orbit, NORAD wants to know about it.  They track and 
>catalog objects as small as a machine screw, because at the relative 

What NORAD can track and catalog depends strongly on range.  Remember
the radar 1/(r^4) equation -- double the target range, and the minimum
visible target size goes up by a factor of 16.

I know that back in AO-10 days, the large L-band radars used for
objects in high orbits like these could see down to about 1 square
meter at geostationary altitude. What they can see while tracking
AO-40 depends on the slant range at the time of the observation, and
also the region of space (azimuth/elevation), doppler and delay that
they searched. These big dishes have *very* narrow beamwidths, so
finding a target in an unknown orbit is nearly impossible.  That's why
it was necessary for AMSAT to develop its own ranging and orbit
determination capability for Phase 3.

NORAD has other sensors that complement the big dish radars. They have
optical cameras that work well on reflective objects at high altitude;
since sunlight provides the illumination, they're only subject to the
1/(r^2) law for the object-to-sensor path. NORAD also has radar
"fences" designed to pick up small objects (previously catalogued or
not) in *low* earth orbit. Whether AO-40 can be seen (or has been
seen) by these other sensors would be interesting to know.

Phil
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