Objective 1: Pick Up Laser Cutter From Air Drop
Check you map and run to the air drop location. There are two guards here, equip your weapon of choice (SD for silent killing or SMG for quick kill) and shoot them both. You must be quick here because there are 5 patrolling guards going to your location. After you picked the laser cutter (and the sniper rifle) go find some place to hide, or move around far to your right to avoid encounter. My suggestion is to kill them all with your rifle (you have 15 ammo anyway).
***GRENADE THROWING STRATEGY***
If you are carrying a grenade or two when climbing the hill at the beginning to pick up the airdrop, and can haul ass fast enough to get to the rocks that line the edge of the air-drop clearing before the patrol comes down the hill, then loiter with intent behind the rocks until the patrol has come down to the airdrop spot. A carefully lobbed grenade right into the middle of them makes them turn tail and run for their lives, and if you time it right you get them all. It's fun to watch them fly up into the air. Seven kills with one piece of ordinance; elegant!
Objective 2: Steal Papers From The Safe
***Note*** I suggest to get the third one first because it will be more easier if the security alarm is deactivated. And the guards on the 2nd objective building have EXTRAORDINARY HEARING ABILITIES! So skip down to three first if you feel more comfortable.
Still move quietly and crawl your way outside and head to Building 2. Check the guy at the balcony of Building 3 using your thermal goggles before moving. You can't do the same thing that you did with Building 3 coz there's a guard on the other side of the room here. And what I hate here is that if you're wearing your thermal goggles and JUST switch your weapons he will quickly stare at your direction. That means if you open the door he will definitely see you. So just continue switching your weapons and wait for him to shout and go up to tell the other guys then run to the corner of the room (the space below the stairs). Equip your pistol (by now you already spent most of your sniper's ammo) and wait for them to go down one by one. They will be staring and throwing grenades at the previous room so you can shoot them at the back. Once all of them are dead, get the papers and head to Building 4.
Objective 3: Disable The Security System & Override Airlock...
Now check your map again, there's only one way to get to the next place... and there are lots of guards on that direction.But there's a way to avoid passing that house over the hill and even the 2 guards on the mountain ridge. Walk on the sides of the hill, that's the left side on your map. If you decided to kill the guys on the house you'll be rewarded with a dragunov (from the guy at the balcony) and some grenades. But if you don't want to waste your rifle's ammo (& your health) then move on the slopes of the hill. Continue moving around the sides until you reach the weather station. Be careful though coz you might fall if you stray too much on the sides.
Position yourself on the southwest part of the weather station (E on the map below) and wait for the two patrolling guards to walk near the ridge. Shoot them down with your sniper rifle so you only have 4 guards left patrolling the area of the station. Get a little closer and wait for them to walk far from the compound (they usually go to the southern part) and shoot them with your rifle as fast as you can so they won't react or shout or do anything stupid that might get attention from the men in the buildings. If you do it right you won't hear the sound of the alarm. Now go near Building 3 (building with #3 in it, duh) and crawl as much as possible. Don't crawl on the side where the camera is, coz there's also a guy on the balcony at that side. Crawl on the left side of the generator. Now when you're inside continue crawling until you reach the room with the security system and a security camera on the side of the stairs. Position yourself under the camera and time its rotation. Go into crouch mode and wait for the camera above you to rotate right into the door then move forward to the computer. The camera will beep but only once and will not sound the alarm, by the time it rotates back you've already deactivated the security system.
Objective 4: Steal Prototype EMP Chip From The Lab
Head to the lab and open the door. Still on crouch mode open the first panel of the air lock door and close it with the switch at the back of that same panel. Then hack the second panel and quickly pop the 2 researchers in the head with your SD. Open the safe room and get the EMP chip and head outside.
Objective 5: Raise The Weather Balloon & Await Evacuation
Check your map (sometimes there's one guard left outside looking for you) then head to the weather balloon and raise it.