Co-Op: When you reach the gravity lift, both players go back to the
shade and melee attack it all the way round to the overshield. This will
take a while. Once done, collect grenades and kill each other one at a time
to create a pile of grenades next the shade. Then pick one up, throw it into
the pile, then quickly pick up the overshield and get inside the shade.
You'll be launched off the map where you can explore the whole area. The
other player can kill themself and respawn up the top of the map.