My thoughts on this are that the UAs are like an early warning system. They site in a shell around Merope and when they detect a ship they scan it and transmit its image back to Merope (hence, why they point at Merope).
The UPs however, wait for a ship to scan them first and then send it a message. My guess would be that they have been sent out from Merope (why they also align with it) in the direction that ships have been detected by the UAs, i.e. towards the bubble. If they are to be found free-floating I would assume they'd be somewhere on the Merope-facing side of the bubble.
Oh btw.
I did have a theory that they were orbiting somewhere in a radius around sol. If uas ate scanning ships add an early warning, ups could be scanning our home and reporting it back to Merope 5c. Maybe the image is stored from a scan of sol.
Sadly no dice looking in Sol or around in uncolonised systems.