Installation 03 (Earth-2042)

Installation 03, also known as Gamma Halo, is one of the seven ring-shaped superweapons that comprise the Forerunners' Halo Array. Located in the Khaphrae system in the Unknown Territories, Installation 03's monitor droid was 049 Abject Testament. The ring has a red and cracked surface, indicating the presence of vast deserts and volcanic activity, but it also features jungles.

Although Installation 03 was originally anchored in orbit around a gas giant for the firing of the Array, by the time of its discovery by the New Galactic Republic in 12 ABY, it orbited a rocky planet, the face of which had been shattered as a result of a fairly recent impact event; the debris from the impact, still aglow as of modern times, has collected to form a dense asteroid field in orbit over the planet as well as the Halo.

Source

 * https://www.halopedia.org/Installation_03