Re: How many satellites are in geosynchronous orbit by now?

(Stuffie is normally in my killfile, but every now and then it's worth
a brief rebuttal anyway...)

In article <1133966629.878320.139070@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Stuf4 <tdadamemd-spamblock-@xxxxxxxxxx> wrote:
> It is the round trip taken together, and not the echo itself, that
>will have a power drop off that tends to decay as the inverse of
>distance to the fourth power.

Which means that the echo *as received* decays that way, barring the
special cases that I mentioned. Which is, of course, what matters for
practical use of radar.

>The problem, as I understand it, is an issue of beam width and angular
>resolution because the same advantage these orbits have in station
>keeping works against you in the tracking task. It is because of the
>lack of relative motion with respect to a ground station that other
>methods are sought.

Nope. The problem exists even when there is relative motion. And
relative motion or lack thereof is pretty much irrelevant to radar
tracking, unless you're using Doppler techniques to pick moving targets
out of stationary clutter... which is important for aircraft tracking on
Earth, especially for airborne radars looking down, but is irrelevant to
space tracking systems looking up.

(I say "pretty much" because there are some space tracking systems that
point in fixed directions and rely on spacecraft to pass over them... but
those are LEO-only, irrelevant to high-altitude tracking.)

>A simple way to invalidate the original statement at issue is to
>consider all of the objects that have been radar tracked at distances
>far greater than GSO.

This stops looking so simple when you consider the resources that are
needed to track them. There have been a *few* quite impressive feats of
spacecraft tracking, notably when it was possible to use Arecibo and
Goldstone in combination. Those facilities are not available for routine
spacecraft tracking, or even mildly unusual spacecraft tracking, and
Arecibo in particular can point at only quite limited areas of the sky.

Note that when Contour was silent after its departure burn, its pieces
were found optically, not by radar.

As it happens, this is a subject I've been professionally involved in, in
a small way. Optical tracking is the method of choice for high-altitude
objects, because radar works poorly at such distances and the resources
needed to make it work halfway well are not routinely available for
spacecraft tracking.
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