The mission parameters are set by Sector Commander Queen T, her experience in combat operations has led her to the conclusion of certain short comings in Combat Unit Capability.
She has re purposed some of her higher performing units to SDU's (Skirm Development Units) to increase the skills of the units she commands.
The SDU pictured was the first in this rotunda to be assigned the role of SDU.
After target accuracy assessment is complete then the highest scoring unit will be re-purposed to squad commander & will train the squad to improve weapons handling.
When on training missions the SDU's take command of the units, using local command control systems to operate their Combatants.
Rather than perform the training in the safety of the Base, QT seen it fit to send the units out to abandoned infrastructure for a number of days to practice with the real & actual threat of enemy encounters.
Ofcourse there are units on guard & they are all quite capable of performing combat operations with most of them being involved in some sort of skirmish already.
Queen T wants their shots to be as accurate as possible. Less shots missed means more dead CPD.