Low-priority deployment missions are ground missions (that is, involving battlesuits) that characters can embark on. They are called low-priority deployments because, while important, the tasks are not of any particular urgency.
These missions are taken from a low-priority deployment center typically located within your capital spaceport.
Once you locate the room, type MENU to get a mission, DEPLOY to deploy your battlesuit, and then ENTER. Because these missions are often for newer pilots, technicians there will make sure your battlesuit is ready to go and tell you about anything you seem to have missed. Once you are ready, type LAUNCH to head to the mission.
Each mission has an objective and it's important to read what it is. The most common low-deployment missions are to destroy transmission towers which control Outsider enforcement drones. In this mission, the drones are ultimately unimportant; your only job is to destroy the tower.
Once your mission has been completed, or if you need to return to the facility for any reason, type LAUNCH again.
Your battlesuit will be undeployed whenever you leave the low-priority deployment room.