Again some free floating thoughts...
I was thinking about the UAs this morning and i guess one of the biggest problems is that we don't know its intention in the game.
How should we find someting without knowing for what to search?
Maybe we should focus some more on the UA and its purpose again. I'm sure there were lots of discussions about it in the older threads, but maybe some new ideas might pop up?
So here is my try for an explanation:
What is the purpose of the UA?
Since there is a massive amount of UAs, you can assume that they are on a "mission" and not just some random probes. They are sent by someone!
They are not here to entertain us, they are doing/preparing something.
From what we know, they are scanning things around them and then sending out this information again.
This could be for two reasons, first searching for any military information, or second for explorational reasons (or both of course).
They always point to Merope, so maybe they are sending these information back to Merope.
It is also possible that they scan the environment for something "suitable" where they can plant down.
They also seem to harm ships and stations, but it is not clear if this is hostile behaviour.
Currently, they are mostly found within the Merope shell. Well, the game spawns them just there, but how did they actually get there?
I don't think that they just appear there, but been brought there.
Ok, now lets assume these UAs are the precursor to a Thargoid invasion (which is totally speculative of course).
Of course, the Thargoids would want to gather as much data as possible from human space, so they are sending out these UA probes.
According to the wiki, the Thargoids have some link to Merope (couldn't verify this), so this might be a good starting point for them.
So first, they are shooting out some probes from Merope to see if there is anything at all (this would be around patch 1.2, where they rarely appeared).
They got a positive feedback and thus prepared something with larger scale. Having thousands of probes (UAs) floating around Merope star might be a bit suspicious, so they sent them to that shell around Merope where they are gahtering and waiting now for further commands (patch 1.4).
Seeing it from this side, the UAs might not be pointing to Merope, but away from it, since they were sent from there.
And maybe, the free floating UAs found in the shell are already aligned to their destination and pointing from Merope to their target (anyone checked this already?). So it might be possible to bring the UA to its destination "by hand" and see what happens?
Also, the glowing symbols on the UA seem to point in 2 directions.
Another thing that bothers me are the Thargoids themselves. Unfortunatly, FD didn't gave us any information about the current human-thargoid situation (which is a big miss in my opinion, since they are a significant part of the lore). The last official thing we actually know about is that they declared peace and even exchanging technological and cultural ideas (3255). Since then, they were never mentioned again... Maybe they are the guys who magically fill up my ship at a station?