Jet Force were some form of galactic law enforcement, formed by the hardly known Earth Empire. It is unknown who led this force, or how big it was, but were known to have engaged Mizar's forces at the cost of their near-extinction except for a few individuals who had escaped the terrible battles, that had claimed their former soldiers.
Juno, Vela and Lupus are part of a team known as "Gemini Squadron"; a group of soldiers who help maintain order within the systems.
Their equipment seems to make them on par with Mizar's brutality of his forces specialising from rocket launchers, to sniper rifles and armor able to endure intolerable thermal heat (i.e lava)