You'll immediately find the Declassify Skull ahead. For this challenge, you'll have to stop the Locust from destroying the Nasssar Embry's Armor. This is the armor sitting on top of the Declassify Skull.
(Declassified Mission) Deploy the three auto-turrets near the armor and prepare to defend it. The armor has a life-bar that will go down as it takes damage. Just stay close to your auto-turrets and prepare to reload them when they're dry. Be careful of the boomers and tickers as well.
Before regrouping with your team mates and pressing the UP button to complete the section, you should check the small room to the right of the area's exit door. You'll find a corpse with a COG tag there.