An Asteroid Mining Unit was a stationary utility station used to extract minerals from asteroids, then eject the extracted material out of the interior of an asteroid field. Slightly smaller than a Strike Cruiser, they were unarmed, but were equipped with shield generators. These stations were unmanned, and had no internal docking facilities.
The Asteroid Mining Unit was built by Byblos Drive Yards, one of many products they produced to aid in mining activities. They were used by a variety of organizations. At least one Asteroid Mining Unit was used during the Galactic Civil War to supply the Empire, XP-MU 3376 in the asteroid field of the Kessel system.
Though the station's description in Star Wars: X-Wing Alliance lists them as being in use by "various," only one Asteroid Mining Unit is ever seen, in the "Family Reunion" mission.