The ship mission Exploration is the default choice of any new or fuelless ship. When performing this mission, the ship's crew concentrates on data from any planet that is being orbited. However, since every ship does this anyway, regardless of mission, it is not necessary to set this in order to get the results. Instead, setting the Exploration mission should be thought of as an easy way to turn off all other missions on a ship.
See also: Out of Fuel.