This character is second in command after the Starbase CO. He/she is responsible for assisting in the command of the Starbase and overseeing the SIM in the CO's absence. SIM administrative duties may be delegated to the XO by the CO as needs arise. The Executive Officer should be the right hand man to the Commanding Officer and capable of stepping in to run the SIM. The qualities that make a good CO apply to this position as well. Executive Officers are selected by the CO.

The XO plays mainly in the Command Center, but can be used all throughout the facility and on any away missions. He is also primarily responsible for the operation and implementation of the support ship, if the base has one.

Examples from Star Trek are Mr. Spock, Cmdr. Riker, Major Kira, and Cmdr. Chakotay.

This is a command position that is heavily featured in nearly all missions and will see many opportunities for activity.