The Archer Combat Drone is an autonomous ground unit in use by the European Federation.
The Archer is the most advanced sentry drone in the world. It is equipped with state-of-the-art sensors and a single minigun, though Archers are often upgraded to carry a THEL (Thermal High-Energy Laser) instead. This is not always a good thing. The THEL has greater firepower than the minigun, but only half the range. This makes THEL upgraded Archers much less effective against gunships - they have to be directly underneath them to fire. THEL Archers are often destroyed by their targets (gunships as well as others) while they are closing the distance to fire their lasers. Minigun equipped drones can begin delivering damage much sooner. In practical usage, the THEL is only an advantage against infantry running in the open, where the drones can win the damage race.
The drone is battery powered, and while the actual battery life is a strictly-guarded secret, it has been rumored that they can operate for days on a single charge. Archers will often be deployed as escorts for Charlemagne Command Vehicles or as sentries.
However, don't expect this quartet of sentry drones be able to win against enemy armor. Archers will easily take down any gunships in their paths, easily making them a necessity to fend off against aerial assaults.