The Pioneer programs were two series of

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

lunar and planetary

space probe Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...

s. The first program, which ran from 1958 to 1960, unsuccessfully attempted to send spacecraft to orbit the Moon, successfully sent one spacecraft to fly by the Moon, and successfully sent one spacecraft to investigate interplanetary space between the orbits of Earth and Venus. The second program, which ran from 1965 to 1992, sent four spacecraft to measure interplanetary space weather, two to explore

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

and

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

, and two to explore

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

. The two outer planet probes, ''

Pioneer 10 ''Pioneer 10'' (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. ''Pioneer 10'' became the first of five artificial objects to achieve the escape velocity needed ...

'' and ''

Pioneer 11 ''Pioneer 11'' (also known as ''Pioneer G'') is a NASA robotic space probe launched on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, the solar wind, and cosmic rays. It was the first probe to Exploration ...

'', became the first two of five artificial objects to achieve the

escape velocity In celestial mechanics, escape velocity or escape speed is the minimum speed needed for an object to escape from contact with or orbit of a primary body, assuming: * Ballistic trajectory – no other forces are acting on the object, such as ...

that will allow them to leave the Solar System, and carried a golden plaque each depicting a man and a woman and information about the origin and the creators of the probes, in case any extraterrestrials find them someday.

Naming

Credit for naming the first probe has been attributed to Stephen A. Saliga, who had been assigned to the Air Force Orientation Group, Wright-Patterson AFB, as chief designer of Air Force exhibits. While he was at a briefing, the spacecraft was described to him, as, a "lunar-orbiting vehicle, with an infrared scanning device." Saliga thought the title too long, and lacked theme for an exhibit design. He suggested, "Pioneer", as the name of the probe, since "the Army had already launched and orbited the Explorer satellite, and their Public Information Office was identifying the Army, as, 'Pioneers in Space,'" and, by adopting the name, the Air Force would "make a 'quantum jump' as to who, really, erethe 'Pioneers' in space.'"

Early missions

The earliest missions were attempts to achieve Earth's

, simply to show it was feasible and to study the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

. This included the first launch by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

which was formed from the old

NACA The National Advisory Committee for Aeronautics (NACA) was a United States federal agency that was founded on March 3, 1915, to undertake, promote, and institutionalize aeronautical research. On October 1, 1958, the agency was dissolved and its ...

. These missions were carried out by the Air Force Ballistic Missile Division,

Army An army, ground force or land force is an armed force that fights primarily on land. In the broadest sense, it is the land-based military branch, service branch or armed service of a nation or country. It may also include aviation assets by ...

, and NASA.

Able space probes (1958–1960)

Juno II lunar probes (1958–1959)

* Pioneer 3 – Lunar flyby, missed Moon due to launcher failure December 6, 1958 * Pioneer 4 – Lunar flyby, achieved Earth

, launched March 3, 1959

Later missions (1965–1978)

Five years after the early Able space probe missions ended, NASA Ames Research Center used the Pioneer name for a new series of missions, initially aimed at the inner Solar System, before the flyby missions to

and

. While successful, the missions returned much poorer images than the Voyager program probes would five years later. In 1978, the end of the program saw a return to the inner Solar System, with the

Pioneer Venus Orbiter The ''Pioneer Venus Orbiter'', also known as ''Pioneer Venus 1'' or ''Pioneer 12'', was a mission to Venus conducted by NASA as part of the Pioneer Venus project. Launched in May 1978 atop an Atlas-Centaur rocket, the spacecraft was inserted into ...

and Multiprobe, this time using orbital insertion rather than flyby missions. The new missions were numbered beginning with Pioneer 6 (alternate names in parentheses).

Interplanetary weather

The spacecraft in Pioneer missions 6, 7, 8, and 9 comprised a new interplanetary space weather network: * Pioneer 6 (Pioneer A) – launched December 1965 * Pioneer 7 (Pioneer B) – launched August 1966 * Pioneer 8 (Pioneer C) – launched December 1967 * Pioneer 9 (Pioneer D) – launched November 1968 (''inactive since 1983'') * Pioneer E – lost in launcher failure August 1969 Pioneer 6 and Pioneer 9 are in solar orbits with 0.8 AU distance to the Sun. Their orbital periods are therefore slightly shorter than Earth's. Pioneer 7 and Pioneer 8 are in solar orbits with 1.1 AU distance to the Sun. Their orbital periods are therefore slightly longer than Earth's. Since the probes' orbital periods differ from that of the Earth, from time to time, they face a side of the Sun that cannot be seen from Earth. The probes can sense parts of the Sun several days before the Sun's rotation reveals it to ground-based Earth orbiting observatories.

Outer Solar System missions

* ''

'' (Pioneer F) –

interstellar medium The interstellar medium (ISM) is the matter and radiation that exists in the outer space, space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as cosmic dust, dust and cosmic rays. It f ...

, launched March 1972 * ''

'' (Pioneer G) –

, launched April 1973 * Pioneer H – proposed out-of-

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

mission for 1974, never launched. Would have used flight spare for Pioneers 10 and 11.

Venus project

(Pioneer Venus 1, Pioneer 12) – launched May 1978 * Pioneer Venus Multiprobe (Pioneer Venus 2, Pioneer 13) – launched August 1978 ** Pioneer Venus Probe Bus – transport vehicle and upper atmosphere probe ** Pioneer Venus Large Probe – 300 kg parachuted probe ** Pioneer Venus North Probe – 75 kg impactor probe ** Pioneer Venus Night Probe – 75 kg impactor probe ** Pioneer Venus Day Probe – 75 kg impactor probe

References

External links

Pioneer (Moon) Program Page
b
NASA's Solar System Exploration

Mark Wolverton's ''The Depths of Space'' online

Space Technology Laboratories Documents Archive

{{DEFAULTSORT:Pioneer Program 1958 in spaceflight NASA programs