Halo Array

''“Installations” redirects here. For other uses, see Installation (disambiguation).'' "Whoever controls Halo controls the fate of the universe."

- Jacob Keyes, quoting his Covenant captors

The Halos (as they are named based on intercepted Covenant transmissions ), alternatively known as the Sacred Rings by the Covenant or Fortress Worlds by their creators, are seven massive ring-shaped installations constructed by the Forerunner throughout the galaxy one hundred thousand years ago as a last resort when combating the parasite known as the Flood. When nothing else could be done, they activated the rings which killed all sentient life within three radii of the galactic center. The Halos are all research facilities and weapons of mass destruction. Each installation was constructed orbiting a gas giant planet, though it is unknown exactly why this was done, but is is speculated that the planet was used as a base for the Forerunners whilst constructing the rings. Once the Halos were activated, the Forerunners also designed a massive shelter called "Shield World" to rescue themselves from the destruction. The seven Halos are designed to be remote controlled from a facility called "The Ark".

Each Halo has a simple designation, consisting of "Installation (01-07)".

Custodial
The installations are designed to be run by advanced Artificial Intelligence constructs specially purposed by the Forerunner. The highest Intelligence on each Installation is a single Monitor. The Monitor's task is to ensure that the Installation runs smoothly, that the Flood stays imprisoned, and that the Installation is ready to fire on demand. They also simulate activation of the Halos regularly. At least one of the Halos has a successful firing record of 1.2 trillion simulated firings, and all seven of the Halos have been fired at least once before as part of the initial purge.

In addition, each Installation contains less intelligent constructs, the Sentinels. The Sentinels serve virtually any purpose necessary to ensure that the Halo works properly; they are also capable of combating small flood outbreaks. Should a major Flood outbreak occur, heavier automations, such as the Enforcers and Sentinel Majors will be created to assist the Sentinels. In the meantime, Constructors are also created to ensure that the Forerunner structures on the Installation are kept in optimal shape, and that they are not damaged by conflict or weather.

Save for the Monitor, all automations can be constructed at specialized Sentinel Production Facilities that float high in the Halo's atmosphere. These Facilities have never been seen (except briefly in the sky above the level Sacred Icon, one can be seen crashing as you exit near the end of the level, you then fight through the remains of it in Quarantine Zone), but they seem to contain limitless materials for constructing any number of automations.

Environment
Each Halo was designed with extraordinarily complex environmental systems and ecosystems. They contain oxygen atmospheres and gravity typical of an Earth-like planet. They also contain complex habitats which include thousands of types of flora as well as various primitive animal life. There are also what appear to be "oceans" on each Halo which house fish and other aquatic life. There was also a desert plateau on the Installation which the Pillar of Autumn crashed on.

The surface of each installation appears to have a "tropical" atmosphere of warm weather and forested mountains and plains. There are naturally occurring weather patterns, including hurricanes and rainstorms. It is unclear how such a complex environmental system was created, let alone how it has remained active for a hundred thousand years.

Dimensions

 * Exterior diameter: 10,000 kilometers (6,210 miles)
 * Exterior circumference: 31,416 kilometers (19,509.336 miles)
 * Interior circumference: 31,275 kilometers (19,421.775 miles)

There seems to be a variation of size and scale in the Halo installations, but the exterior diameter for most appears to be about the dimension mentioned above. All currently presented evidence points to Installation 05 being smaller than this, although the validity of this claim can be disputed. The thickness of Installation 04, from one side to the other, is about 320 kilometers (198.72 miles), so the other Installations probably also waver around that value. The thickness of the Installations is around 22.3 kilometers (13.9 miles) thick.

Technology
Each Halo has a Control Room located somewhere on the ring. The Control room serves as the central chamber for the Ring's activation, and serves to control all functions of the ring. It is the Installation's command center.

Each Installation contains a number of basic Structures, including a "Library" which contains an "Index." The Index is the key to the Installation's activation. They also contain a "Silent Cartographer" which serves as a map to the Installation's Control Room. , as well as numerous Flood Containment Facilities and Flood Research Facilities. Every Halo has live Flood specimens that are kept for study. Any Flood outbreak is caused when these specimens somehow escape containment.

The Installations also contain advanced transportation grids for use by the Monitor. These Grids allow instantaneous transportation to any place on the ring for the Monitor and any other persons or things it chooses. The Installations are also riddled with travel conduits, presumably for the Monitor to move around quickly.

Function
The Halo system is complex, but the Halo's main weapons can be activated individually from within itself, or all of them simultaneously from a control center known as The Ark. In the event of a major flood crisis, the Installation's Monitor will seek out a "Reclaimer" who they will immediately transport to the Library. They must navigate to the Index Chamber, and then retrieve the Index. The Monitor then stores the Index for safe keeping, and they immediately proceed to the Control Center. Once at the Control Center, the Reclaimer must insert the Index into The Core of the Installation (protocol does not allow the monitor to activate the ring itself, it can only be activated by a reclaimer). Once this happens, the main weapon fires. The Main weapon is then amplified by the Phase Pulse Generators built into the ring, and the weapon expands in an unknown form of energy (possibly a gamma ray burst). The particular form of energy of at least one Halo (Installation 04) has an effective radius of approximately 25,000 light years (147,000,000,000,000,000 miles/147 quadrillion miles). The activation also triggers the other six installations, and their systematic activations cause a chain reaction which affects the entire galaxy, eradicating all forms of sentient life.

History
The Halos were created a few hundred years after the Flood was discovered by the Forerunners, because their builders saw that their current isolation and containment procedures were not adequate to stop the spread of the Flood. Little is known of their extensive history, (At least one was functional for 101,217 Local years) but after exhausting every other tactical option, their creators had no choice but to activate the Halos' main weapon, and destroy all sentient life in the galaxy.

The seven halos then remained relatively dormant for one hundred thousand years (Though at least one of them experienced a major Flood outbreak) until one of them, Installation 04 (known amongst fans as Alpha Halo), was discovered by the theocratic alien superpower, the Covenant. The Covenant, who revered the Forerunner as gods, believed that the Halo's main weapon was actually a "divine wind" meant to propel them on a path they called the "Great Journey". This idea caused them to recklessly release the Flood of the installation, an act further complicated by the arrival of the human vessel UNSC Pillar of Autumn. A massive four way melee ensued between the Covenant, the Forerunner Constructs, the Flood, and the Humans. This finally culminated when the Human Spartan known as the Master Chief detonated the fusion engines of the Pillar of Autumn on the surface of the Installation, destroying it completely.

Later, a second Halo, Installation 05 (known amongst fans as Delta Halo), was discovered. On this Halo, the Flood had already been released somehow, and a similar conflict erupted. This conflict has yet to be resolved. However, the Installation was almost activated, and now the six remaining Halos are on "Standby mode".

Unknown Halos


Installation 04 and 05 are the only two Fortress Worlds yet discovered in the Halo Universe but when we look at the Monitor naming scheme, they offer more proof as to the existence of other Halo's.

Looking at the number in the Monitor's name, 343 Guilty Spark, 343 is seven to the third power. Seven being a number seen frequently in Bungie games and mythology. The number "2401", from 2401 Penitent Tangent the Monitor of Installation 05, is seven to the fourth power.

When the numbers of each Monitor are examined, a pattern emerges: each seems to be seven raised to the power of the installation number minus one; therefore this table to the right can be established.

Astronomy
The "Ringworld" of Halo is much smaller than Larry Niven's Ringworld. While the diameter of Niven's ringworld is close to the diameter of Earth's orbital of 300,000,000 km, the 10,000 km diameter of Halo is much closer to the diameter of Earth itself, which is 12,756 km. Ringworld has a star similar to our sun in its center, and Halo is orbiting a planet, but does not encircle it.



Besides the very beautifully sculpted landscape on Halo's surface, the sky is also worthy of attention. Depending on the viewpoint, you can see the star, a moon (called Basis), a gas giant (called Threshold), and the band of Halo itself, which looks like a street into the sky.

In the course of Halo 1, neither Threshold nor Basis is reachable, all action takes place on or in the Halo. In Halo 2 there is a multiplayer level on Basis, and there is a campaign level on a gas mining facility in Threshold's atmosphere.

Trivia

 * On Halo PC, on the menu, look closely at the Halo before it starts moving. somewhere on it can be seen the letters Gny Sgt Marcus, referring to Marcus R. Lehto.
 * The Halo textures for both Halo 1 and 2 are the same, and are both symmetrical. Thus, when you look straight up, a shape in the clouds of the Halo resembles a Grey alien. It could have been put in there on purpose, although it might be a coincidence.
 * Halo: Ghosts of Onyx describes the Halos as being the "sword" of the Forerunner, as Shield World was their "Shield." This description is mysteriously similar to the lines Cortana says on the Halo 3 Announcement Trailer; "I am your shield, I am your sword."
 * In the clouds of Halo, on every level, you can see the face of a human (presumed to be Frank O'Connor, the Bungie Update Author).

Related Links
Installation 04
 * Control Room
 * The Silent Cartographer
 * Alpha Base
 * The Library
 * Flood Containment Facilities

Installation 05
 * Control Room
 * The Library
 * Quarantine Zone
 * Sentinel Wall
 * The Temple
 * Flood Research Facilities
 * Relay Station
 * Sentinel Production Facility