1. Photograph satellite: easy, medium, hard 
2. Obtain telemetric data: medium, hard 
3. Retrieve satellite circuitry: medium, hard 
4. Minimize scientist casualties: easy, medium, hard 
5. Plant bombs in fuel rooms: hard 

In the easy section, there is no time limit, but in the medium and hard difficulty levels, the whole mission is timed and a clock at the bottom of your screen delivers the time. You have 7:30 minutes (in medium, and 8:30 in hard) to meet all of your required objectives. That means a lot running and killing, baby. Also, in every room there is a green card, i.e. the satellite circuitry, and important telemetric data which you'll need to recover. The satellite circuitry lies around on tables, and is pretty easy to spot, while the telemetric card is harder to find. Security cards are in the hands of the scientists. If you run and scare them, they'll drop the cards, otherwise the cards are in their hands. Usually the guy in the deepest corner has it. 

Again, in the easy level, you just need to make it out, keeping a few scientists (and yours truly) alive. But in the hard level, you'll have beat the time limit, collect all the circuitry, take a picture of the satellite, and blow up the fuel rooms. Like the instructions say, concentrate on rooms H4, C3, K2, and A1. In the middle rooms there are two body armor vests, so keep an eye out for them. 

Go to the first room and kill off about three soldiers guarding it. They will be in range and if you're kill them fast enough, and no scientists should get in the way. Pick up the required cards (two green data ones resting sitting on a table on the left) and the security card on the floor. 

After the first room you'll come to a split in the hallway, take a right, and pass along a side bridge, by the rocket. At least two men stand behind the door that leads from the bridge to the hallway, so when you open the door, shoot fast, strafe right. Then strafe left in front of the doorway and finish the other guys off. 

At the end of the hallway that turns left, there are a few barrels. A few soldiers may also appear. Instead of shooting them, shoot at the two explosive barrels in the corner, if done right, all of the nearest barrels will blow. Give yourself a lot of room, like stay at the bottom of the stairs. Approach the corner of the wall without revealing yourself. Lean out and shoot about three or four guys in the distance. Be wary of grenades. Take out one soldier at a time. There are more barrels just around that corner, so if the barrel explosion you caused didn't set them off, make sure the enemy fire doesn't either. 

You're now ready for room two, containing at least three soldiers who hide behind the door on the right. Another will be in your sight as soon as the door is open. One green data card lies on a computer card just on the other side of the door, so grab it. Grab the security card on the floor as well. As many as three more guards may enter the room, so watch out. Go up the stairs and out. 

Another split in the hall appears before you, and you should strafe to the left side of the hallway and kill the guy on the right without exposing yourself to the intersection. Now turn left, press R and Right C, and lean to see a soldier ducking behind a crate. Now turn and go to the right where you'll open a door to a bridge with a load of soldiers on it. More appear on the other side of the door. Strafe and shoot, strafe and shoot. After that, enter the room, follow the corridor that leads up a short set of stairs and then lead to the third room where more soldiers will meet you at the top of the stairs. Don't forget to wave. 

The third room. No soldiers will appear initially. Enter and head right to the bald scientist in the corner. He will have a DAT card, which will complete objective B. Great, now turn around. Go to the far side of the tall computer just next to the door. Another bald scientist is there, so you'll need to grab the security card from him. Objective C has now been completed. You should have no less than 1:40 on your clock if you're half way decent. Three guards will stand in your way as you pass through a T shaped split in the corridor. Turn right, and get ready. 

After the third room, turn right and kill the few soldiers on the bridge. After that, a clan of gunmen are ducking, hiding, and shooting. Follow suit. Crouch down and wait until there is no gunfire, and then stand up and shoot. Kill the first guy on the left and hide behind that crate. Then duck and shoot a few times quickly, before they start tossing grenades. 

Room four has the satellite. It's easy to spot because of the blue side paneling; switch to your camera and take a picture. All objectives are met for easy and medium. Walk up the stairs and prepare for another battle. There are no less than a dozen men, plus Ourumov, who has a brief case behind them all. While it's relatively easy to kill off the soldiers, Ourumov will shoot and not miss until you run toward him. And you're gonna take a few hits, so hopefully you've acquired those vests. Half way through the tunnel he'll run. You're on a time limit, so rush at him as soon as you kill all of the soldiers. 

Chase carefully after him, but slow down before you turn the corner left in the final T-shaped hallway. At least three guardsmen are there. Strafe right and left to avoid their shots. Turn left, go out the door that leads to a bridge, and then to another door. Enter it and pass through a hallway with an oval shaped room. A guard will stand at each side. Shoot one, then the other. More should appear. Go right into the next room and kill the few guards that are in the middle of a giant computer circle. Plant the plastique, ascend the three stairs, and turn left past the room you entered. Don't forget to run like a crazy fiend. Take a right to an elevator, and that's the ball game, spy guy.