Dr. Owen was a human scientist stationed at Galileo Base.
When Galileo Base was under attack from the Covenant, she send out a distress call to UNSC forces. So Sarah Palmer dispatched Fireteam Crimson to help defend the base. After the foces were defeated, Owen helped getting the base up and running again.
When the base was under attack for a second time she explained to Fireteam Crimson that base defenses were down due to Dr. Alexander and that he used the power of the defenses to activate his mini-reactor.