Editing Installation 04

{{Era|Forerunner|HCW}}

<center>'''''Installation 04''' redirects here. For other uses, see [[Installation 04 (disambiguation)]]''</center>

|image=[[File:H2A-AlphaHaloDiscovery.jpg|350px]]

|location=[[Soell|Soell system]], in orbit around [[Threshold]]<ref name="VIS">'''[[Halo: The Essential Visual Guide]]''', ''page 6''</ref>

|anchor=Threshold/[[Basis]]<ref name="VIS"/>

|function=Galactic sterilization/Flood containment and research

|caretaker=[[343 Guilty Spark]]

|constructed=Before c. [[100,000 BCE]]

|destroyed=[[2552#September|September 23, 2552]]

|diameter={{Convert|10000|km|mi}}<ref name="VIS"/>

|surface width={{Convert|318|km|mi}}<ref name="VIS"/>

|gravity=.992G (approx)<ref name="VIS"/>

|surface temperature=-23°C to 40°C (-9°F to 104°F) (controlled)<ref name="VIS"/>

|atmosphere=1 ([[Wikipedia:Nitrogen|N₂]], [[Oxygen|O₂]])<ref name="VIS"/>

'''Installation 04''', also known as '''Alpha Halo''', was one of a series of gigantic ring worlds, the [[Halo Array]], left behind by the enigmatic, technologically advanced, and apparently extinct [[Forerunner]]s.

The [[Covenant]] reverentially described Installation 04 as either the '''First Holy Ring''' or the '''First Sacred Ring'''. After its destruction at the end of the [[Battle of Installation 04]], [[Installation 00|the Ark]] started to construct [[Installation 04B|a replacement for Installation 04]].  

The climate of Installation 04 was very similar to [[Earth]]'s climate. There have been hurricanes over the oceans on the ring.<ref>'''[[Halo: The Flood]]''', ''page 14''</ref> The weather was, however, extremely unpredictable - rain and snowfall could occur at random, leading [[Cortana]] to wonder if the weather was intentionally irregular, or if it followed a pattern such as snow being deliberately made at the control room to slow the Flood.<ref>'''Halo: The Flood''', ''page 107''</ref><ref>'''Halo: Combat Evolved''', campaign level ''[[Assault on the Control Room (level)|Assault on the Control Room]]''</ref>

With a diameter of 10,000km and a surface width of 318km, the ring has a surface area of 3,180,000km².

===Ancient history===

Installation 04 was built by [[Installation 00]]'s [[Foundry]] before [[100,000 BCE]].<ref group="note">In ''Halo: The Flood'', 343 Guilty Spark states that the ring was 101,217 years old in 2552. However, this was measured in the Soell system's local time.</ref><ref>'''Halo: The Flood''', ''page 238''</ref> When the [[IsoDidact]] activated the Array at the [[Forerunner-Flood war]]'s conclusion, ending the centuries-long conflict, Installation 04 was the first to fire,<ref>'''Halo: Silentium''', ''String 38''</ref> followed shortly after by the other six Halo rings. Installation 04 lay dormant for a hundred thousand years, with [[343 Guilty Spark]] and his [[Sentinel]]s ready to keep the [[Flood]] confined in the [[Flood containment facility|Flood containment facilities]] and keeping the infrastructure of the Halo in perfect working order.

After eons of uneventful existence on Installation 04, 343 Guilty Spark eventually found himself bored. For his own amusement, Spark began an experiment in which he evacuated entire sections of the Installation into space; according to Spark, these were experiments to measure the geologic effects of exposure to the vacuum of space and the eventual biological recovery of the evacuated sections, in order to gain insight into emergency response scenarios.<ref>'''Halo: Combat Evolved Anniversary''' - ''[[Terminal/Halo: Combat Evolved Anniversary#Terminal 4|Terminal 4]]''</ref>

Around [[40,000 BCE]], an [[unidentified alien vessel]] crash landed in [[Sector 1215]]. Sometime prior to the crash the ship started broadcasting a distress signal.<ref name="terminal5">'''Halo: Combat Evolved Anniversary''' - ''[[Terminal/Halo: Combat Evolved Anniversary#Terminal 5|Terminal 5]]''</ref><ref name="time">'''Halo: Combat Evolved Anniversary''' - ''[[Terminal/Halo: Combat Evolved Anniversary#Terminal 6|Terminal 6]]'' (343 Guilty Spark: ''"I have now endured 60,000 years without word from outside the Array."'')</ref> After attempting to translate it, [[343 Guilty Spark]] blocked the signal, as no communication revealing the location of any of the Halos was allowed.<ref name="terminal5"/> After no lifeforms exited for several days, Spark had a large sarcophagus constructed around the vessel.<ref name="time"/>

[[File:Autumn Arrival.png|thumb|right|250px|The {{UNSCship|Pillar of Autumn}} arrives at Installation 04.]]

In the conclusion of the battle, John-117 detonated the ''Pillar of Autumn''<nowiki>'</nowiki>s [[Fusion drive|fusion reactors]] in order to destroy the ring. The explosion critically damaged the superstructure below it; the resulting shockwave and damage to the ring's systems destabilized the ring, shattering it into pieces.<ref>'''Halo: Combat Evolved''', campaign level ''[[The Maw]]''</ref><ref group="note">The particulars of Installation 04's destruction differ throughout its various depictions. In ''Halo: Combat Evolved'', ''Combat Evolved Anniversary'' and most [[terminal]] depictions, a portion of the ring next to the ''Autumn''<nowiki>'</nowiki>s explosion is sent flying to the other side where it bisects the ring, further splintering the superstructure. The most noticeable change is in the flashback portion of the level ''[[The Heretic]]'' in ''Halo 2 Anniversary'', where the fragment is no longer propelled to the other side and the ring simply shatters, with the explosions spreading in both directions of the epicenter in a chain reaction. The blue lights on the outer surface are also seen going out in this version. The [[Terminal/Halo 2 Anniversary|''Halo 2 Anniversary'' terminals]] give two versions of the ring's destruction, the first (in Terminal 4) being identical to ''Halo: Combat Evolved Anniversary''<nowiki>'</nowiki>s [[Terminal/Halo: Combat Evolved Anniversary|Terminal 11]], which is closer to the original ''Halo: Combat Evolved'' mechanics, although the ring's shattering is more violent. The second version, shown in Terminal 12, is closer in line with the depiction in ''Halo 2 Anniversary'' version of the flashback in ''The Heretic'' and lacks the shard being blasted to the opposite side.</ref>

Installation 04 was the first Halo installation encountered by humanity, as well as first to be destroyed. Its destruction triggered the activation of a portal leading to [[Trevelyan|Shield World 006]] within [[Onyx]], and also caused [[Installation 00|the Ark]] to start constructing a [[Installation 04B|replacement ring]].

===Post-destruction===

[[File:H2A - Alpha Halo remains.jpg|thumb|right|250px|The burning wreckage of Installation 04, surrounded by vessels of the Covenant armada in the aftermath of the battle.]]

There is now a large field of debris where Installation 04 was, though a few large chunks of the ring remain.<ref>'''[[Halo 2]]''', campaign level ''[[The Heretic]]''</ref> Some smaller pieces of the Installation 04 have landed on Basis, while others have burned up in Threshold's atmosphere upon entry.<ref>'''[[Halo 2]]''', multiplayer map ''[[Burial Mounds]]''</ref>

The UNSC's peace treaty with the Covenant forbids either party from landing on the remains of Installation 04.<ref name="nf1"/>

When the ''Pillar of Autumn''<nowiki>'</nowiki>s reactors went critical, Installation 04 attempted to activate a safety measure and make a slipspace jump. However, this self-preservation protocol was only partly successful, and only a small portion of the ring managed to enter slipspace before the ''Autumn''<nowiki>'</nowiki>s reactors overloaded and destroyed the ring. The surviving fragment of the Halo reentered normal space in the vicinity of a red giant star some distance away from the [[Orrichon system]] and was caught in the giant star's orbit.<ref name="wp shard">[https://www.halowaypoint.com/en-us/universe/locations/halo-ring-fragment '''Halo Waypoint - Universe''': ''Alpha Shard'']</ref> This fragment was home to a unique element apparently created by the heat of the ring's explosion and not found elsewhere in the universe. The element was later refined and used in a [[bioweapon]] unleashed in a [[terrorist]] attack on [[Sedra City]].<ref name="nf1">'''Halo: Nightfall''' - ''Chapter One''</ref>

====The ''Mona Lisa''====

{{Main|Skirmish on Mona Lisa}}

[[File:TML - broken_Halo.png|thumb|250px|A segment of the broken ring.]]

Following the return of the survivors from the battle, the Office of Naval Intelligence learned of the Flood lifeform. Section III sought to establish a research laboratory in order to control the Flood parasite and possibly weaponize it against the Covenant. A science team headed by Major [[John Smith]] was authorized to take command of the [[prison ship|prison vessel]] ''[[Mona Lisa]]''. After bringing a group of Covenant prisoners aboard, they jumped to the wreckage of Alpha Halo in the Soell system. Some Flood specimens had survived the ringworld's destruction and were recovered to be experimented on both human and Covenant prisoners. However, the Flood soon broke quarantine and infected the ship. ONI later dispatched a [[prowler]], the {{UNSCShip|Red Horse}}, to assess the status of the ''Mona Lisa'' under the pretenses of investigating Halo's debris field. On October 25, 2552, the prowler was forced to destroy the overrun vessel with a [[Shiva-class nuclear missile]].<ref>'''Halo: Evolution - Essential Tales of the Halo Universe''', ''The Mona Lisa''</ref>

===''Anniversary'' redesign===

While the design of the Halos has stayed largely consistent across all post-''[[Halo: Combat Evolved]]'' media, Installation 04 underwent a significant visual overhaul in ''[[Halo: Combat Evolved Anniversary]]''. The entire superstructure of the ring has been redesigned. To wit, the surface features are completely different and much more pronounced, including additions such as rows of prominent prongs lining the ring's edges and large-scale patterns of bluish light, in contrast to the more subdued original design in which the features on the outer surface appear largely flat due to the immense scale of the ring. This redesign has not been carried over to post-''Anniversary'' media: the prongs are absent from [[Installation 03]] in ''[[Halo 4]]''; [[:File:FUD-HaloRing.jpg|a visual allusion]] to the Halos in ''[[Halo 4: Forward Unto Dawn]]'' follows the original design; in ''[[Halo 2 Anniversary]]'', Installation 04 has received some visual changes (including prominent blue lighting in the circular patterns on the ring's outer surface) but is otherwise closer to the original version than the ''Halo: Combat Evolved Anniversary'' redesign.

*It is possible to see falling debris from Installation 04 on the map [[Burial Mounds]].

File:AlphaHaloview2.jpg|''Pillar of Autumn''<nowiki>'</nowiki>s engines detonate, destroying Installation 04.

File:Halo anniversary menu concept 1.jpg|Concept art of Installation 04 in ''[[Halo: Combat Evolved Anniversary]]''.

File:Installation 04 Terminal.jpg|Installation 04, as seen in a [[Terminal/Halo: Combat Evolved Anniversary|Terminal]].

**''[[Terminal/Halo: Combat Evolved Anniversary|Terminals]]''

*''[[Halo 2 Anniversary]]'' {{C|Flashback}}

**''[[Terminal/Halo 2 Anniversary|Terminals]]''

*''[[Halo 5: Guardians]]'' <small>(Simulation only)</small>

<references group="note"/>

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[[Category:Halos]]

[[Category:Installation 04| ]]