Orbital defense platform

An Orbital Defense Platform was a large UNSC space station used to defend locations of great importance, typically planets. Stations were frequently placed in geosynchronous orbits and deployed in groups, or clusters, of 2 to 5.

The well-equipped and large bridge of an ODP was suitable for directing large-scale engagements. Such was the case when Fleet Admiral Sir Terrence Hood directed UNSC forces from a ODP during the First and Second Battle of Earth.

Facilities
Internally, the stations were remarkably spacious, complete with high ceilinged common areas and a monorail system to move personnel and equipment. In addition to numerous small craft bays there were two docks for larger ships, such as freighters or even frigates. The design incorporated many features against potential hostile boarding action, including security stations and small arms racks situated at strategic locations.

Armament
The primary armament was a Mk. V "Super" MAC gun, capable of causing severe damage to even a shielded Covenant warship with a single hit. As with starship-mounted MACs, a platform's cannon was commonly controlled by an AI.
 * ''Curiously no sources indicate the presence of additional weapons, such as point defense cannon commonly mounted on UNSC warships. However, the possibility cannot be ruled out,

Powerplant
ODPs did not mount the power generation equipment necessary to fire their main armament. Instead, they received power from ground-based generators. A possible strategy to neutralize the formidable ODPs would be to disable the generators via ground assault.

Reach
By August 2552, Reach was protected by twenty ODPs. During the Battle of Reach, marines and Spartans were deployed to protect the orbital platforms' planetside power generators but were ultimately unable to do so against determined enemy assaults. The disabling of the defense platforms was a major factor on the battles outcome.

Earth
The outbreak of the Human-Covenant War prompted a massive expansion of Earth's defenses. Even as late as the Battle of Reach preparations had not yet been completed. By October 2552, some 300 ODPs were operational. Many of Earth's ODPs were named after points of interest that they roughly kept station over.

A portion of the 300 platforms saw action at the First Battle of Earth. Athens Station and Malta Station were each destroyed by an Covenant Bomb placed by Covenant boarding parties, with Cairo Station narrowly avoiding the same fate.

The ODPs were also used in the Second Battle of Earth, but the Covenant might have already destroyed numerous stations when Truth led a second fleet to Earth.

Known ODPs

 * Athens Station UNSCDF-ODA144
 * Cairo Station UNSCDF-ODA142
 * Malta Station UNSCDF-ODA143
 * Nassau Station