Start "The Ark" mission. After entering the first building take a left into another door. You will be in a curved corridor. On the inside is a Terminal.

After activating the bridge in "The Ark" mission to let your friends cross the gap, turn 180 degrees to find the Terminal. Note: It does not open until you activate the bridge/

In the third building after defeating the Scarab in "The Ark" mission, kill the group of sleeping Covenant. Follow the corridor down. You will reach a door in front that is locked. Immediately on the left is an open door. Go through and walk straight off. Turn 180 degrees to find a secret room with the Terminal.

Enter the first tower standing on the lift in "The Covenant" mission. Face the access panel and turn left. Jump over to find the Terminal.

Land your Hornet on the second tower in "The Covenant" mission. Walk towards the entrance. When you see the locked door, turn 180 degrees to find the Terminal.

When in the third tower standing on the lift in "The Covenant" mission, face the access panel then turn right. Jump over to find the Terminal.

After reaching the end of the first cave in the "Halo" mission, hug the right wall. You will see a building. Jump up onto the walkway and turn to the left once you are inside to find the Terminal.