An Orbital Space Enviorment refers to a multi-player map that takes place in a space enviroment. There are multiple maps that fall into this label, and the name isn't used to describe one map, but a category of maps. It is said that individual space maps do not have their own names as they are in an area around Dust, the main planet and setting for Starhawk.
There is an O.S.E. currently playable in the beta, being one of the first maps playable. It is currently the smallest map, and is very vertical map having mutiple levels over a small area. There are two detached platforms floating away from the main platfrom that overlook each team's home base.