When ready, fly to, and dock with, the Omega 4 relay to launch the suicide mission.
After the numerous conversations and story scenes, you will find yourself with a pair of your choice in the Cargo Bay looking at one of the Collector defence drones – an Oculus. The Oculus is basically a flying eye that will shoot lasers and zoom all over the place. Use your heavy weapons on it and anything else (biotics or ammo) you have at your disposal that is effective against armor to take it down quickly. At several points it will exit the zone through the holes in the Normandy’s hull and reappear elsewhere so make sure to constantly scan your surroundings until you find it again. After the Oculus has taken sufficient damage, you will be treated to another scene.
Following the scene, you will once again find yourself in the cargohold facing off against a second Oculus. The strategy is the same as before, but this time there is a lot less cover for you to hide behind and the majority of it is destructible. There are a few low-lying platforms on either side of the room you can use, but because the Oculus hovers, it will get behind your cover pretty easily so you will need to keep moving. There are a few crates of Power Cells lying around, so don’t be afraid to use your heavy weapons liberally. When it has taken sufficient damage, a scene will play.