Artist depiction of the Cassini-Huygens space craft near Saturn.
A space probe is a robotic spacecraft which does not orbit the Earth, but instead is sent out into outer space, typically to discover information about a planet, or another object. A spaceprobe may approach an object, fly by it, orbit it, or land on it, or enter interstellar space.
Currently, there are 15 missions involving space probes in operation.