The links to the specific missions on the wikipedia page have some expert conjecture, based on observations by amateur skywatchers, so we have a good idea that it's being used to launch military surveillance and communications satellites, as well as being used to test new hardware. Which is all rather broad and generic, but if it were aliens, it's not like they'd tell us anyway.

Even if it were actually confirmed that OTV-1 launched a military surveillance satellite, we still wouldn't know how good it is at that other than some hard limits due to physics (mirror size and atmospheric interference).