While other psycommu systems merely read brainwaves and translated them into machine code to control weapons, the Angel Halo harnessed the power of 20000 "Psychickers", all controlled by a single Newtype in the middle, and used them to "devolve" the human mind through the use of "psycho waves". It would literally force an adult mind to think like a baby and even further back. It was used to attempt to mind wipe all inhabitants of Earth. Afterwards, an extraterrestrial pathogen called "Angel Call" would be released to eliminate humanity.
Angel Halo had no outer defenses, it was only guarded by a Zanscare fleet. However, the effects of the structure's systems prevented potential attackers from getting close.
Crossbone Gundam Ghost
According to Curtis Rothko, Angel Halo was originally conceived as a joint effort between the Jupiter Republic and Zanscare Empire to transport 100,000 Jovian immigrants to the Earth Sphere. However the Zanscare Empire quickly seized Angel Halo, and turned it into a weapon.
The Angel Halo was used by the Zanscare Empire in an attempt to mind wipe the inhabitants of Earth. However the interference of the League Militaire prevents this and the Angel Halo is disabled.
Crossbone Gundam Dust
Debris from the Angel Halo still remains in space, as various parts begin to enter the Earth's atmosphere, either burning up on entry or crashing onto Earth.
The wreckage eventually fell onto Earth, creating a large impact zone. Seventy years later, during the events of G-Saviour, the Congressional Armed Forces is using the impact site to hide a secret mobile weapon factory under Project Raven.