Re: Earth orbiting monitoring question.
Suddenly appears in Earth orbit with no energy emission or space-distorting phenomena that would upset sensitive scientific experiments on four continents? That sounds like deliberate stealth technology to me. After all, even if you've been using your wormhole generation system for a couple of centuries and it's totally mature engineering it has to be easier to get it more or less right, then use conventional drive systems to adjust your velocity and position, than get all that precisely right before setting off.
Mind you, "Earth orbit" is a fairly wide term; the moon is in Earth orbit and it would be a darn sight harder to see than Telstar if it weren't so big.
So, you say a "giant UFO" – about how big? 500 metres, five kilometres, five hundred kilometres? And what albedo? If they're deliberately trying to hide it there's no reason why it needs to radiate or reflect anything much in the visual bands, and very few amateur astronomers work in the infra-red (if they're serious about stealthing, since they know where potential observers have to be they could direct their waste energy outwards, away from the planet; in which case they'd only be noticeable when they eclipsed a star, and who's going to suspect that wasn't a beetle flying close to the telescope?).
The larger end of my size range would eventually be detected by gravity measurements (ultimately, if they're not too far out, even by the variation of satellite orbits). However, unless you can get it on visual, calculate its distance and rough size (from how long it occludes a particular star, since you know its speed), just about any explanation for your strange readings is going to be considered before "ruddy great alien spacecraft used not to be there and now is".
Radar (and other active detection systems) nowadays is directional. No more omnidirectional transmissions and see what you get as reflections. It sweeps, certainly, but its aimed. Air traffic control isn't going to scan for loose meteors; it wouldn't know which runway to bring them down on, anyway. Almost all of space is a disappointment to scan, anyway; just the little bit right close to our planet is full of interesting junk that might fall on us. If it were foolish enough to choose geostationary, it would probably be spotted pretty fast (as well as risking a lot of the aforementioned junk)
Obviously all this assumes they don't want to be seen, that they're deliberately sneaking in. If they just happen to achieve perfect synchronisation by coincidence they could well be painted fluorescent orange, with 10kW running lights every twenty metres. Even the aiming scopes on the big reflectors are likely to notice that, and even a post-graduate writing his thesis on nebular formation in the lesser Magellanic dust clouds is likely to report it (as some fool messing around with fireworks and spoiling his observation, to be sure; but mention it nevertheless).
Amateurs tend to find more comets and near Earth objects a) because there are more of them and b) because they scan all the sky, not just the regions they expect something interesting (yes, like a nuclear missile) to come from.