Do you see the security is being provided by Imperial Marines, as I'd assume
a Research Station would have a suitable guard force?
I'm in the "it depends" camp, too.
Obviously, an "Imperial" research station would logically be guarded by Imperial Marines, or Army, personnel. But, the station is also highly secret--even "black"--so, maybe some non-military "black" force is in charge. The equivalent of the Empire's Delta Force, Rainbow (from Tom Clancy), Seal Team Six, Army Rangers or Green Beret.
Or...since we're dealing with research that is highly illegal in the Imperium, maybe the powers that be want to put some distance between themselves and the research station. What if they're using Merc? Corporate Security types. Hired Guns.
Or...maybe the Empire shut this research station down a long, long time ago, and it's been reactivated by the Zhodani? The zho's are operating a base within the Imperium, and it's allowed to exist because the previous base was so top secret.
Or...let your imagination run wild.
It really depends on what fits best in your game? If you're not running an on-going game,then what appeals to you most? What do you want to play?
Take the adventure as a base and mold it into what you want/need to play.