Aliens are building a "space highway" through our solar system. They love our Jupiter, so they decided to put gas pump with bar on its orbit.
After realizing that we cannot do anything about it and if asked, they can fake our agreement, they decided to put such gas pump there without even trying to contact us.
The question is: Who on Earth, and how fast, will realise that something alien is happening around Jupiter?
Background for space highway: It is set of precalculated dimensional jumps which will always throw you out near something with gravitational pull. Then you, as driver of vehicle, can decide if you are going to use gravity of such object for next jump or if you will make a stop here and refuel. (Or take kids for a snack to McJupiters)
Aliens use mixture of FTL communication and normal radio waves. Neither the ships nor gas station try to hide themselves, because they assume "everything is legal"
Such gas pump opened for business half an hour ago. Who can realise something is going on?
And especially, can average space fan with customer level equipment see something there? Assume size of such pump as big as Phobos
This is "local highway" - assume 10 000 vehicles going throught the jump during an Earth day. The gas pump can hold up to 15 space vehicles at a time. Common alien ship is about as big as ISS is. Pump itself has artificial gravity.
The pump has "standard" beam, which you approve in your ship computer and all navigation is done for you. Which means, that most sub-FTL communication is done directionally