The phrase "unmanned mission" refers to a type of task or operation that is carried out without the presence or involvement of humans. Instead, it is accomplished using machines or technology. Full definition
It will also assist in preparing for further future unmanned missions, including a Mars Sample Return mission, and possible future human exploration. (politics.co.uk)
Anything that could be learned from a manned mission could be learned at far less cost by unmanned missions. (firstthings.com)
While NASA's Johnson Space Center manages monitored debris threats for spacecraft related to U.S. manned missions such as the International Space Station, the responsibility for unmanned missions managed by NASA falls to the Conjunction Assessment Risk Analysis, or CARA, team operating out of NASA Goddard. (sciencedaily.com)