Planetary Missions

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay

Lunar Robotic Missions

The five Lunar Orbiter spacecraft, launched in 1966 and 1967, were all successful and obtained photographic coverage of about 99 percent of the Moon.

Luna 17 landed on the Moon on November 17, 1970 and released the rover Lunokhod 1, which operated for 11 lunar months before instruments in its sealed body froze up.

Lunokhod 2, an improved version, landed in 1973. It lasted four months and travelled 37 kilometers.

Venus and Mercury

Mariner 2 was the first spacecraft to fly by Venus, in 1962. It had no cameras but did record temperature measurements and showed conclusively that Venus was extremely hot.

Apart from the antenna on the base of the spacecraft, necessary because of the long distance back to Earth, Mariner 2 is very similar to the Ranger series of spacecraft sent to the Moon. It was based on the same design.

Venera 9 and 10 became the first Venus orbiters in October, 1975, arriving on the 22nd and 25th, respectively. Upon arrival, they dropped the first landers to return pictures from the surface.

Cometary Missions

Thwarted by inability to get funds for a full-scale mission to Halley's Comet, U.S. space scientists put together a makeshift mission. Since 1978, a spacecraft, the International Sun-Earth Explorer, had been on station between the Earth and the Sun. In 1982, it was nudged out of its orbit, sent on a series of Earth and Moon flybys that set a record for complexity, then launched on a path to intercept Comet Giacobini-Zinner and Comet Halley. Although it lacked cameras, it returned information on dust and gases from the comets as well as how they interacted with the solar magnetic field.

Note that these are anything but neat Keplerian orbits! There are two reasons:

The Japanese Sakigake and Suisei missions to Halley's Comet


Pioneer 10 and 11

Voyager 1 and 2

The Titan III C was the launch vehicle for Voyager 1 and 2.



Cassini is the last of the big-time spenders, at least for a while. Missions that cost $200 million during the 1970's now cost over a billion dollars. The emphasis now is on smaller, cheaper, faster missions. Cassini is seven meters tall, four meters across and weighs 5600 kilograms, about comparable in size and mass to a medium-sized truck. It was launched in 1997 and used several flybys of Venus and Earth to gain enough speed to get to Saturn. Its original launch velocity supplied only one-fifth of the total energy required to get Cassini to its destination; the rest came from planetary encounters. It went into orbit around Saturn in 2004 and dropped a probe named Huygens onto Titan. The Huygens probe is the large circular object visible behind and to the right of the spacecraft. The long boom to the left, 11 meters long, carries a magnetometer for studying Saturn's magnetic field.

Illustrations of Important Rockets and Spacecraft

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Created 23 February 1998, Last Update 14 December 2009

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