Additional missions assigned by Briggs | Mission 12 - Site F Splinter Cell: Blacklist Guide

You can select missions from Briggs in two different ways - by selecting the appropriate dialogue option during the conversation (for the first time, after you complete the prologue) or by choosing the appropriate category on the World Map. These are the only missions that can be played solely in the co-op mode because, in many places, the important actions to be performed (hacking into the system, opening a door), require the cooperation of two players. When it comes to their characteristic features, in many respects, these are similar to the missions in the single player campaign mode. In some situations, it may be requisite to stay in hiding, whereas in others, it may be a more sound choice to take up open action. The completion of all of the missions without raising the alarm is, of course, possible, but many of these depend on the actual skills and the willingness of both teammates to repeat the failed actions.

I recommend that you take up these missions only after you purchase improved gadgets, with particular focus on the sleeping gas grenades and the crossbow, upgraded to the maximum level. Being dressed in a stealth suit and the better variations of the firearms (no necessarily for killing enemies, but rather for, e.g. destroying sources of light, cameras and drones) also will help.