往程 outbound leg (of a bus or train journey etc) 往复 to go and come back; to make a return trip; to reciprocate (of machine part) 往复运动 reciprocating motion ..
If you're living in a country where you have to walk for several hours or even a day to get toa clinic it's extremely unlikely you would bother tomake the returntripa week later to get the result of a check-up.
Plaything for our future robot overlords? (Let's hope it's not the last one.) The success of the mission will depend on a couple things, namely: how the returntrip goes (it should make it back to California's Vandenberg Air Force Base via autopilot... sometime) and whether the thing can be re-launched quickly enough.