This will be a Main Mission in the Southwest area just underneath East Mall. The southwest area is for players who are between level 11 and 15. It's recommended that you be at least level 14-15 before attempting this mission if you're going solo.
When you arrive to the mission it's a bit confusing on how to get in. There will be a yellow tarp covered fence that doesn't have barbwire on top that you can jump over to get started. (Next to a white car)
One you've hopped over that you'll be in a courtyard with a few enemies. All level 12 regulars and one purple enemy. Clear them out and then head inside the NOA Headquarters.
As soon as you enter and pass the front desk you'll enter a mall looking area. There will be another handful of enemies here that scale in level with one purple enemy on the 2nd floor who shoots RPGs at you. clear out a couple waves here and then proceed to the 2nd floor to open a door and head up to the 3rd floor.
There will be another group of enemies to kill before pressing on to secure the top floor of the atrium. Once the top floor is secured, press on to the roof where you'll have to manually establish a connection for a computer. You'l have to align 3 satellite dishes while fighting off enemies. Take your time to clear people out before aligning the dishes.
Once all 3 antennas are aligned get to cover because an Elite enemy will appear with a grenade launcher and a ton of armor. I used an LMG to work away at his armor and stayed in cover away from the grenades. Once you kill him you'll need to head back to the lower levels. Another open room with a group of enemies to clear out.
Once the room is clear you'll be told to "Escort a module" of machinery. You don't actually have to stay with it, so kill everyone and stay in cover until the room is clear. Then head to the module to change it's course and get it moving again, which will spawn another group of enemies to clear out.
After this you'll head to a research lab. Once you pull the lever to open the door expect a TON of enemies. Some of them with RPGs again. Once you clear them out you'll have to remove a a component from the machine you were escorting. When you attempt to do this you'll be interrupted by the power going out briefly and an explosion occurring on the upper level. Get to cover because another grenade launcher wielding Elite enemy will be arriving. This one has even more armor and his grenades are incendiary based so the fire can reach you even even behind cover. You'll also have to worry about regular enemies flanking you, so a defensive skill like the turret could help out here.
Once you've killed everything and survived you will need to return to the module you escorted through the mission and remove the component from it. Once you grab it the mission will complete and your achievement will pop.