The GDI Orbital Ion Particle Beam Cannon was a superweapon developed and created by many scientists of the Global Defense Initiative. There were approximately ten in orbit over Earth 2 under the Ion Cannon Control Network.
The exact functionality of the Ion Cannon was revealed towards the end of the third Tiberium War. Utilizing the Ionic Tiberium in the atmosphere, and combining it with cosmic radiation, and varying other factors, the Ion Cannon combined them into a single beam of explosive power. This reaction usually resulted in a blue glow above whatever area was about to get hit, giving 5 seconds for people to move out the way, though usually, seeing this and being under it was too late. Following the end of the Fourth Tiberium War, and the removal of Ionic Tiberium, the Ion Cannons all stopped working.
To be fired at an earth-dwelling target, the Ion cannon first had to link up to the closest ICCC at the closest GDI base. Once it has accomplished this, the Ion cannon could be used within a certain range of the area to cripple hostile attack and defense forces (though should an Ion cannon be turned to aim into space, a control centre is not required).
When activated against anything within the planet's atmosphere, the Ion Cannon shot down eight ionizing beams to the surface. These beams would slowly spin towards each other, damaging anything they cross. Upon colliding, all eight of the beams amassed their energy at the ion cannons firing mechanism, then blasted down to the surface. Upon impact, anything within range of the Ion cannon was absolutely annihilated, people vaporized, vehicles exploded and buildings blown apart, with the force of a 500KT nuclear weapon. Though this was the mode most commonly seen in the battlefield, the secondary mode of the Ion Cannon allowed it to fire a large beam once charged, allowing for a quicker and more immediate response to battlefield threats.
Despite its power however, firing to Earth 2 took approximately seven minutes for the ion cannon to prime, having to locate battlefield co-ordinates, charge itself, and move itself into position to fire. Usually after it had accomplished this it was ready to fire again within three minutes, as moving the ion cannon was the most time consuming process. This was why firing the ion cannon into space took such little time, as it did not require co-ordinates and did not have to move.
Though they weren't the most powerful weapons created, the ion cannons were still superweapons that require special permissions to use. Any commander in the field had to gain special permission from him to utilize the ion cannon as to avoid misuse of the weapon.
The Ion Cannon was most famously used in Destari, where a hidden Liquid Tiberium bomb created by the Brotherhood of Nod under a fake Yuri base was detonated when the beam made contact, spreading tiberium all over the country. Minutes later the Ion Cannon fired again at alien transports approaching Earth 2 from space, though this didn't do much damage to them.
The last ion cannon strike took place during the Fourth Tiberium War, as one fired at an approaching Scrin ship, sending it burning to the ground. When the war ended, the satellites drifted in orbit. They were going to be taken down until Pieboy6000 returned, and converted them into the less powerful, but more maneuverable Laser Uplink Cannons.