Installation 00

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Installation 00, also known as The Ark, is an enigmatic Forerunner installation from which all the Halo Installations across the galaxy can be activated simultaneously. In addition, it functions as a safe haven from the Halo network's strategic pulse, and as a facility to construct replacement Halos. It was first mentioned by 343 Guilty Spark at the conclusion of Halo 2, where he explains the fail-safe protocol of Installation 05 and the standby modes of the seven rings after its unexpected shutdown. The Ark is about 218 (exactly 262,144) light years from the galactic center. In comparison, Earth is 25,000 light years from the galactic center.

History
Installation 00 is a part of the Forerunner construct designed to wipe the Flood from the Galaxy. Located about 262,144 light-years outside the Milky Way galaxy center. Installation 00 is safe from the Halo effect (as it is referred to by the Forerunners in the terminal transcripts) that kills all sentient lifeforms; the main Forerunner behind its use was Didact. The purpose of the installation is to remotely activate every Halo ring, from outside the blast radius. This is a fail-safe system that is only activated by an aborted firing such as the one that occurred at the end of Halo 2. In addition, Installation 00 can also function as an automated factory to construct replacement Halo installations, thereby insuring that the Halo array is always ready to fire.

"Every vessel we can fill, we send to the Ark. I dare not cease the mission. Not now, not until I've done all I can. Each one of these souls is finite and precious."

- --Transcript of a message from the Librarian to Didact, interpreted post-cataclysm and retrieved from the first Terminal on the level "The Ark"

Apparently, while the rest of the Forerunners attempted to defeat the Flood through any military way possible, a plan B was also approved to be put into the works, which included the construction of the Halos, Shield Worlds like Onyx, and The Ark.

In this final resort plan, the Librarian was to index every sentient species in the Galaxy, and bring some to the Ark, and then presumably some Forerunners, and these last sentient species would hide in the Ark's secret location, until the Flood starved and they could go back to the Milky Way.

However, things did not go as planned, as the Forerunner military AI Mendicant Bias turned on the Forerunners, and began assisting the Flood. Mendicant Bias knew of the Ark, and how to access it through the Key Ships, but did not know of its exact location. The Forerunners then constructed another military AI, Offensive Bias, in order to devise the best possible defense against Mendicant Bias and his fleet. The Librarian detonated all of the Key Ships in her command, and spent her last days upon a mountain near the site of the portal to the Ark, for aesthetic reasons.

Layout and Function
Installation 00 resembles a massive wheel with a series of eight curved arms, similar to an octopus or squid. The Ark Core is the stripped remnant of a material-rich planetoid, asteroid, or other celestial body used for the construction of the Halos, which the Ark constructs. The entire upper surface is terraformed, with oceans, forests and even a large desert, where Master Chief first makes landfall. The structure is the largest Forerunner construct seen in the series, possibly a hyper-structure knowing that fortress worlds are 10,000 kilometers in diameter approximately. A simple inspection of the holographic representation reveals it to be anywhere from 90,000 to 100,000 kilometers (55,890 to 62,100 miles) in diameter.

The two shown primary functions of Installation 00, are as a remote for activating the entire Halo network with safety of being out of the Halos' range, and as an automated construction facility for the creation of replacement Halo installations (ensuring that the network continues to operate even if any rings are destroyed).

Most interestingly, the Ark is not actually in the Milky Way as noted by a stunned ODST soldier at the start of the level The Ark. As such, it's outside the believed range of any Halo installation. The Ark also has an artificial sun floating above it. An observer can see this more clearly on the level Halo when looking up at the sky.

The Foundry
The Strip Mining Moon is the open area at the heart of Installation 00, which is surrounded by a void, and is the automated factory for replacement Halo installations. This void conceals the Halo Foundry, which constructs the Halo Rings and sends them to their orbital destinations. Raw materials for the process are supplied by a planetoid roughly 1/3 the size of Earth. The moon is large enough to make several replacement installations, as seen in Halo 3 when it produced a replacement for Installation 04.

Cooling Systems
The intense heat generated by the Ark's Foundry, where the Halo rings are constructed, heats the Ark up so much that multiple cooling stations are needed. At least two systems span a snowy gorge at one point. The systems are long, and they curve up like bridges. Above the systems are small bridges, as well as two stations on each side. An example of a cooling system are the two on the Halo 3 multiplayer map Narrows.

Environment
Along with most Forerunner constructs, the Ark consists of an atmosphere similar to Earth, comprised of oxygen and nitrogen. This makes all Human-Covenant War species able to live on this planet (excluding Grunts who depend on methane tanks to sustain life) and the Flood as well. Also, like Earth and the other Installations, weather radically changes on the Ark.

The Ark has a habitable surface on each of its spokes, and on the majority of the inner circle just outside of the Foundry. The landscapes and biomes are as diverse as those of Earth and even of the Halos; consisting of deserts, taiga and forest as seen on The Covenant, and deciduous forests as seen in Isolation. Several bodies of water are dotted around the area as well. As such, the Ark can sustain its own ecosystem, providing a variety of habitation for many kinds of life. If the Halos were fired, all forms of life could thrive and reproduce in the Ark's highly varied ecosystem, eventually being able to return to the Milky Way to recreate a full food chain on that planet. The diverse locations may also assist in the studies of the Flood in a natural, but isolated, environment.

As the Ark is outside of the galaxy, isolated in a black void of space, there are no nearby natural sources of light to power the Installation and facilitate the survival of biological organisms on its surface. To counter this problem, the Ark is equipped with an artificial structure consisting of a bright, sun-like light, with several metal arms jutting from its center. From aerial pictures of the Installation, it seems the light source "scans" over certain areas to generate day/night cycles, further contributing to the growth of vegetation and controlling weather patterns.

Portal
An important component of the Ark which serves as a medium of transportation, the Portal is a Forerunner creation which is designed to open a Slipspace rift to enable access to Installation 00.

As first seen in the Halo 3 Announcement Trailer and numerous other promotional materials, this construct was originally thought to be the Ark itself; however, this was disproved with the release of Halo 3. The Portal was partly uncovered when Regret's carrier destroyed New Mombasa in Halo 2, and completely excavated by Covenant Loyalist forces later on. In Halo 2, the Prophet of Regret moved his carrier above New Mombasa and deployed a large ground army. UNSC Marines were subsequently able to beat the Covenant to a retreating standstill, apparently causing the Prophet to attempt a dangerous atmospheric Slipspace transition.

By the time of Halo 3, Covenant Loyalists began excavating the portal from the crater and were able to completely uncover it. The Prophet of Truth activated it at the conclusion of the level The Storm. It formed a massive portal, in which the Forerunner ship immediately entered (presumably carrying Truth), followed immediately by the Covenant Loyalist ships. At the end of the level Floodgate human and Covenant Separatists forces resolved to follow Truth's ships through the portal, and ended up at Installation 00. At the end of the game, the damage caused to the Installation caused the portal to collapse, severing the Dawn in half as it passed back through. The forward section, in which Thel 'Vadam had been inside of, made it back to Earth, plunging into an unspecified body of water. Humans soon rescued Thel. The aft section of the Forward Unto Dawn, containing Master Chief and Cortana did not make it through the portal, and were stranded in an unknown location of deep space.

Guilty Spark meets Mendicant Bias
This transcript is taken from the third Terminal which is found in the game. It basically tells that 343 Guilty Spark is being warned for accessing Installation 00's systems and is warned that even though he is the Monitor of Installation 04, he has no right to be accessing systems on the Ark. He also learns that Installation 00 has the capability of constructing another Halo Installation and manages to stop the AI from sending Sentinels after him.

'''Warning: Your intrusion has been logged.

'''04-343 (errant): Excuse me?

'''Your intrusion has been logged. And now it has been halted.

'''04-343 (errant): On whose authority?

'''Advice: Any further attempt to access [insects under stone] will result in your immediate addition to local Sentinels' targeting ledger.

'''04-343 (errant): Vexation! I am the Monitor of --

'''Judgment: Your authority means nothing here.

'''04-343 (errant): Impatience!

'''04-343 (errant): I have told you who I am. Who are you?

'''All our makers once held dear. [Alexandria before the Fire]

'''04-343 (errant): Sincere apology. But how --

'''Explanation: This facility is host to the [Librarians'] final --

'''04-343 (errant): The archive is intact?! Then our makers' plan --

'''But also maintains [bellows, crucible, castings]

'''04-343 (errant): A what?

'''[bellows, crucible] --

'''<font color="#0000cc">04-343 (errant): A Foundry?

'''<font color="#0000cc">04-343 (errant): For what purpose?!

'''<font color="#ff3333">Warning: Your intrusion has been logged.

'''<font color="#ff3333">Advice: Any further attempt to access will result --

'''<font color="#0000cc">04-343 (errant): Indignant!

'''<font color="#ff3333">-- immediate addition to local sentinels' targeting ledger. '''

(terminal gets overridden)

More commands show up, including this somewhat creepy message said by Mendicant Bias:


 * <tt>I. SEE. YOU. RECLAIMER.</tt>

Trivia

 * Within the Halo Graphic Novel, in the short comic Second Sunrise Over New Mombasa, a transmission is intercepted between the Covenant assault forces stating that once the humans were dealt with in the First Battle of Earth, they would start uncovering the Ark. There is also, of course, the strongly supported theory that human life originated in East Africa, usually said as the Great Rift Valley.
 * In the fifth server of the Iris VMC it was stated that the Ark was built to protect humanity from the Flood and the activation of the Halos.
 * In the real world, Ark of the Covenant which according to the old Testament contains the stone tablets of the ten commandments, is the holiest object of the Jewish faith. The Ark of the Covenant is popularly believed to lie somewhere in East Africa, albeit in Ethiopia rather than Kenya.
 * The "Ark" seen in the announcement trailer is structurally identical to the Forerunner sanctuary described in the final chapters of Ghosts of Onyx (albeit on a much grander scale), complete with fourteen metal fins and a brilliant, blue-white portal in the ground. However, it is shown without the thirteen concentric rings rising around the portal, which means that it was either built without them or they will rise as the structure opens.
 * During the level The Ark, 343 Guilty Spark mentions that the Ark is 218 (262,144) light years away from the center of the Milky Way. As the Milky Way is around 100,000-120,000 light years in diameter, the installation is beyond the reaches of galactic space, thereby keeping anyone who is on it safe from the firing of the Halos. This is reinforced in the Halo 3 level The Covenant, by 343 Guilty Spark after the arrival of the Flood on the Ark. He says "The Ark is out of range of all the active installations. Priority: We must contain this outbreak."
 * A member of HBO] estimated the size of the Ark by comparing its size to a Halo installation and [[Earth and estimated its size to be approximately 90,000 to 100,000 kilometers in diameter.
 * In the Art of Halo 3, it showed a picture of a giant firestorm sweeping across the entire Ark as the replacement Halo fired, thus doing "a number on the Ark". Though this outcome is unconfirmed as the Ark's final fate was not seen in Halo 3.
 * The entirety of the Ark is never seen in game; only petals or the center of the Installation are seen. This contrasts the Halo Installations, which were usually given full-bodied debuts for their entrances.
 * The Ark has some similarity to the concept of an Alderson Disk. However, an Alderson disk is much larger and has a star in the center.
 * A thread on Bungie.net theorised that the Ark may spin on its axis to create gravity. It was supported by the fact the Milky Way galaxy is visible in the sky during the campaign level The Ark but not on the multiplayer levels such as Valhalla.