The above image shows the orbit layer in Prebuild with one Hovertruck.  When the Prebuild phase is complete, the player will have several new options available on the Hovertruck Toolbar including the ability to build solar panels.  Solar panels are a great source of energy and should be build in every available place on an asteroid, but don't forget to defend them!  The other object that appears is an Outpost.  Outposts are used to "tightbeam" units from one Outpost to another or "Launch" them from one layer to another.