https://hackaday.com/2015/06/05/building-your-own-sdr-based-passive-radar-on-a-shoestring/

Use the SatCom traffic as your illumination.

On Wed, Feb 21, 2018 at 9:41 PM, shadow at shadowgard.com (via tml
list) <xxxxxx@simplelists.com> wrote:
> I've been noodling with an idea for some time, and I figured I'd ask
> this list for some info.
>
> Basic idea is somebody who claimed a big section of land on a
> frontier world. Or maybe it's long settled, but low pop.
>
> I'm assuming that on a place like this you can claim a fairly large
> hunk of land. Multiple km on a side.
>
> He's quite a bit paranoid, and likes his privacy. So he worries about
> getting tracked to various places on his property.
>
> I'm assuming a satellite net for communications, S&R, weather and
> some limited mapping purposes.
>
> Anyway, I've been thinking about ways you can detect an air raft of
> similar vehicle.
>
> Anything active will be a dead giveaway that someone is looking. So
> radar/lidar are mostly out.
>
> Visual from orbit can be dealt with in various ways, (like flying
> thru narrow canyons/valleys when the angle is wrong for satellites.
> Ditto for flying (carefully) under the cover of trees (virgin forest
> is good for that sort of thing. :-)
>
> So visual & IR aren't too bad to deal with.
>
> With "civilian" grade sensors (as opposed to military or ISS grade)
> an air raft or larger "truck"/RV type vehicle doesn't emit enough EM
> to track easily.
>
> That leaves the CG & propulsion. What Piper called "lift & drive".
> They are probably detectable to some extent with grav sensors of some
> sort.
>
> Question is, how detectable and at what range.
>
> I'm gonna go with "speed of plot" in the end, but I'm interested in
> how "reasonable" folks think my ideas are.
>
> So, I figure that from orbit, the best you can do is "yeah, there's a
> grav vehicle operating in [large area]". Tens of miles or more.
> (gravity is a fairly weak force after all)
>
> Get closer and there are probably "home on grav" missiles and the
> like, but you'd have to be within a few miles.
>
> So I'm planning on assuming that absent a tail, or IN/ISS sensors he
> can in fact count on it being hard to tell where on his property he's
> going if he takes some fairly simple precautions.
>
> Anybody see a problem with that?
>
> --
> Leonard Erickson (aka shadow)
> shadow at shadowgard dot com
>
>
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