The Type M-17 Photon Turret was a series of static defense platform present on colonies belonging to the United Federation of Planets.
These highly effective automated weapon systems were only capable of being construction when photon shell production began on a colony. Though it may seem to go against Federation principles of non-violent actions, its generally accepted that the more remote frontier colonies face a greater number of threats which can only be countered through the use of force or at very least, the appearance of force. These circumstance allow this class of photon turret to be deployed.
The turret fired fired self propelled photon artillery shells at targets that are identified by the colony's sensor net or by other mobile units within sensor range. However, before deployment of the system, a colony commander must accept the production costs of photon artillery and accept the consequences such production has on the colonial economy. (TOS video game: New Worlds)