Orbital defense platform

Orbital defense platform (ODP), or orbital weapon platform, is an armed space station designed to defend a planet or other astronomical body, either from enemy attack or asteroids and space debris. Most human colonies maintain basic, coilgun- and missile-based orbital defenses; most of these are operated by the UNSC Aerospace Force or local civilian agencies. Important colonies are defended by arrays of weapon platforms with heavy Magnetic Accelerator Cannons capable of gutting Covenant capital ships.

UNSC ODP types

 * Moncton-class: early to mid-HCW era "workhorse" heavy platform, self-powered but point defense was lacking.
 * Viery-class: Reach-type superheavy MACs, really good but have issues like reliance on power beamed from surface platforms.
 * Manila-class: Moncton predecessor, Earth's first platforms in the Insurrection era; phased out at Earth by 2552 but still found on colonies.
 * Tanais-class: light defense platform, often found on colonies
 * Antioch-class: "off-brand" ODP class often used on lesser colonies, more such classes may exist though colony defenses may even be makeshift
 * Torres Vedras-class: launched c. 2570; Moncton successor as a a heavy all-rounder; better point defense, power and anti-plasma disruptor field generators
 * Civilian/planetary government platforms: miscellaneous models mostly used for meteor defense and against pirates/rebels. Usually missile-based, though some are equipped with light to medium coilguns.
 * Makeshift ODPs: older and/or damaged capital ships stripped of slipspace drives and converted into orbital defenses/system patrol vessels. Some war-era warships were retired this way while the UNSC built up their Navy post-war.

All ODP types (like all space stations) have stationkeeping thrusters, can adjust their orbits and even move about to some extent, but they are very slow and sluggish and most lack the capability to leave orbit.