Installation 04



Installation 04, or Alpha Halo as it is called by humans, is one of the seven massive Halo fortress worlds built by the Forerunner.

Details
Planet of Orbit: Threshold

Monitor: 343 Guilty Spark

Status: Destroyed

History
Installation 04 was built around 98,665 BC (It was 101,217 years old in 2552). It is unclear why Threshold was chosen specifically, but this is likely due to the large number of Forefunner machines already operational in Threshold, namely the network of Gas Mines.

The Installation was activated sometime thereafter, and all Forerunner and Flood (save those in captivity in the Halos) were killed. Installation 04 lay dormait for millenia, with 343 Guilty Spark and his Sentinels keeping the Flood confined in the Flood Containment Facilities and keeping the infastructure of the Halo in perfect working order.

This all changed around August of 2552, when the Covenant discovered the location of Installation 04 after The Battle of Sigma Octanus IV. They sent the Fleet of Particular Justice to secure the Halo in preparation for the arrival of the holy city High Charity. After The Battle of Reach a single UNSC cruiser, the UNSC Pillar of Autumn, arrived at the Installation around September 19, 2552 and was promptly shot down. At the same time, the Covenant accidentally unleashed the Flood from captivity. The ensuing four-day melee that took place all over the ring was called The Battle of Installation 04. Humans, Flood and Covenant fought massive battles against one another as the Forerunner Constructs tried to control the outbreak by activating the Halo. In the end, a single human called the Master Chief detonated the Autumn's fusion reactors, destroying the Halo.

Only a handful of humans and Covenant survived the battle. 343 Guilty Spark floated through space until he met a group of Covenant on Threshold. Inspired by his words, they began a heretic rebellion against the greater Covenant. Installation 04's destruction is seen as the first step in the chain of events that led to the Civil War of the Covenant.

There is now a large field of debris where Installation 04, though a few large chunks of the ring remain, some pieces of the Installation 04 have landed on Basis and burnt up in Threshold's atmosphere.

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 in Threshold's atmosphere. That level is set on a Forerunner gas mining facility.