Head to the giant UNSC vehicle and talk to the office on the action deck. Grab the jetpack once prompted then wait for the mammoth to move. Man the turret on the left side and clear out the covenant position near the cliff. Next, head to the right and use the turret to clear the position there. You have to recover the target designator by foot so jump down and clear the area then recover the designator. Use it to take out the drop ship. Take out the enemy Wraith that will appear then finally target the particle cannon and watch the fireworks.
Return to the Mammoth or ride the any vehicle you have. Upon reaching the next enemy position, wipe out the enemy forces and destroy the shield generators for the Mammoth to pass through. After destroying all shield generators, return to the Mammoth to proceed.
Wait until you have the second particle cannon in range. Aim for it using the designator then wait for it to be destroyed. More enemies will appear and the Mammoth will be stranded. Jump down to the ground and drive the railgun-mounted Warthog. Destroy several waves of Ghosts and Wraiths until you get the command to board the landing ship on the hill.
Fight your way to the tractor beam and get inside the ship. Kill all enemies inside then destroy the core. Jump off the ship then use the jetpack to break your fall. Once done, return to the Mammoth. Enjoy the ride until a pile of boulders halts your advance. Pick up the sniper rifle then clear the area to the left on foot.
Move carefully as you explore the ridge as there are a lot of enemy snipers here. As you proceed, more will appear on the hills and mountain sides. You can use your jet pack to reach vantage points as well but it may backfire if you're not careful as you'll be visible on higher ground as well.
Continue to the covenant structure and fight your way to the objective point. Enter the structure and follow the sentinel as it leads you to an elevator. Continue following the sentinel until you reach the console controlling the particle cannons.
After the scene, Cortana will disappear. Backtrack a bit and a light bridge will appear to the right. Follow the straightforward path to trigger a scene. After the scene, pick up Cortana and make your way to the elevator. Defeat the enemies and before taking the elevator, turn to the right to find a terminal
Head outside then drive one of the Scorpion tanks there. Be careful of the Wraiths' explosive charges. Continue until you're hampered by a solid shield. Like before, you have to destroy the shield generators to proceed.
Once the shield is down, continue on foot then pick up the designator near the edge of the cliff. Aim for the gravity well and deliver the payload to complete the mission.