Space Probe

The scores probes launched since 1959 are grouped into families, which usually encompass craft similar by design, mission, or both. The United States National Aeronautics and Space Administration (NASA) has launched a series of interplanetary probes (Pioneer, Voyager, etc.), of lunar probes (Ranger, Surveyor, Lunar Orbiter), of planetary probes (Mariner, Viking, Pioneer Venus). The former Soviet Union's probe families were Luna (Russian for Moon), Mars, and Venera (Russian for Venus). Although all Soviet (and, later, Russian) efforts to land a space probe on Mars have failed, only Soviet spacecraft have landed on the surface of Venus.