1. Destroy control console: easy, medium, hard 
2. Settle the score with Trevelyan: easy, medium, hard 

The main principles of beating this level are rather simple, ol' chap. 1. Find the computer console that controls the satellite dish and destroy it. 2. Follow closely behind Trevelyan once you find him. He will run from you the entire level, occasionally stopping to shoot or double back. By staying as close to him, you'll reach your goal faster, which to settle the score (i.e. kill him, difficult to guess that one, wasn't it?). 

You start off on a cul-de-sac wing. Back up to your left and pick up a piece of body armor and then run forward along the hanging bridge in front of you. Pick the center of the path with your PP7 and, without using the site, start shooting. You will hit an enemy soldier running toward you. Pick up his two ZMGs and keep running, because at the top of the wing are at least three more soldiers just like him. Kill them and grab their guns. Turn left, run to the staircase to the center platform, and descend. Half way to the first descending staircase you'll discover Trevelyan has set the auto destruct to explode. You have three minutes to turn it off. 

That at least helps to set your priorities straight. So, go to the first platform, making sure to kill the single guard, take the staircase on the left down to the lower platform, and you'll see two shacks. Go left; the computer console is in it. The door will be open. There are at least two guards, each packing. 

Be careful not to enter right away. Trick the soldiers to come out by running in front of the door and then getting out of the way. An automatic machine gun is aimed at the door. When you are ready, point your gun up, target, and blast away. Another auto machine gun is inside. It won't set be set off until you're more than half way in. Step in about three steps and shoot the remaining guys, if there are any. Always check your back, too. New soldiers will run down the steps when you're not looking. 

A giant piece of machinery is to your left; behind it is the computer console. You should have more than a minute left. Blow the second turret up and then hustle to the other side of the machine. You'll see the computer console. Shoot it to stop the antennae and the cradle from blowing up. Objective A is achieved. 

Trevelyan is next. A few more guards will approach you from the door you entered. Kill them, and get used to taking a little bit of damage. You now need a body vest. Leave the shack from he door you entered and go to the other shack, which is nearly identical inside. Swing around the machine and pick up the body armor. 

Head back to the other shack. Settling the score with Trevelyan means that you chase him across the entire cradle at least once. The biggest trick to this chase is to stay as close as possible to him. He'll run around the cradle at least twice if you're decent. He stops inside the shack, at the bottom of the staircase beneath the shack, and at the top of the cradle to shoot at you. 

He will eventually run to the very bottom of the cradle, to the antennae. He'll drop down to the antennae platform, a mere 10 feet across, and then sneak up on you. Get out your biggest, fastest gun (duh, the ZMG), and make sure it's fully loaded before you jump down. He'll immediately start shooting. Reply with as many shots as fast as possible. You'll have to knock him off the antennae to win this battle (or settle the score, as the game says). If you're left standing and he falls off, you win the battle and beat the game. Yahoo! 

Now you can beat the game on the medium and hard levels if you dare. By beating the 18th level in the most difficult mode, you will open up the 19th level. If you beat the 19th level, you will open up the 20th level. If you beat that in the most difficult level, you'll open up the 007 mode, enabling you to modify enemy control, like health, accuracy, etc.