Pioneer 10 (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. It was the first spacecraft to traverse the asteroid belt and the first of five artificial objects to achieve the escape velocity needed to leave the Solar System. The mission was managed by NASA Ames Research Center in California, and the spacecraft was built by TRW Inc. The spacecraft was built around a hexagonal satellite bus with a 2.74 m (9.0 ft) diameter parabolic high-gain antenna and was spin-stabilized about the antenna axis. Electrical power was supplied by four radioisotope thermoelectric generators (RTGs), which produced a combined 155 watts at launch. Pioneer 10 was launched on March 3, 1972, at 01:49:00 UTC (March 2 local time), aboard an Atlas-Centaur rocket from Cape Canaveral Launch Complex 36A. Between July 15, 1972, and February 15, 1973, it became the first spacecraft to pass through the asteroid belt. Imaging of Jupiter began on November 6, 1973, from a distance of 25 million km (16 million mi), and the spacecraft returned more than 500 images. Its closest approach to Jupiter was on December 3, 1973, passing within 132,252 km (82,178 mi) of the planet. During the mission, its scientific instruments investigated the asteroid belt, the environment of Jupiter, the solar wind, cosmic rays, and the outer heliosphere. The last signal from Pioneer 10 was received on January 23, 2003, after declining electrical power from its RTGs left the spacecraft unable to operate its radio transmitter. At that time, it was about 80 AU (12 billion km; 7.4 billion mi) from Earth.
Mission background
History In the 1960s, aerospace engineer Gary Flandro of NASA's Jet Propulsion Laboratory proposed the Planetary Grand Tour, a mission concept that would take advantage of a rare alignment of the Solar System's outer planets. Although the concept was ultimately realized in the late 1970s by the Voyager program, NASA decided in 1964 to test key elements of the mission by sending two probes to the outer Solar System. An advocacy group, the Outer Space Panel, chaired by James A. Van Allen, developed the scientific rationale for exploring the outer planets. NASA's Goddard Space Flight Center proposed a pair of "Galactic Jupiter Probes" that would pass through the asteroid belt and explore Jupiter. The spacecraft were planned for launch in 1972 and 1973 during launch windows that occurred for only a few weeks every 13 months; launching outside those windows would have required significantly more propellant. NASA approved the mission in February 1969. Before launch, the two spacecraft were designated Pioneer F and Pioneer G; they were later renamed Pioneer 10 and Pioneer 11, respectively. They formed part of the Pioneer program, a series of uncrewed U.S. space missions launched between 1958 and 1978. Pioneer 10 and Pioneer 11 were the first spacecraft in the program designed to explore the outer Solar System. Their primary objectives were to investigate the interplanetary medium beyond Mars, study the asteroid belt, assess potential hazards to spacecraft passing through it, and explore Jupiter and its environment. More than 150 scientific experiments were proposed for the missions. The final instrument payload, selected through a series of planning meetings during the 1960s and completed by early 1970, was designed to image and perform polarimetric observations of Jupiter and several of its moons, conduct infrared and ultraviolet observations of Jupiter, detect asteroids and meteoroids, determine the composition of charged particles, and measure magnetic fields, plasma, cosmic rays, and zodiacal light. Radio tracking during the spacecraft's occultation by Jupiter would provide measurements of the planet's atmosphere, while precision tracking data would improve estimates of the masses of Jupiter and its moons. NASA Ames Research Center, rather than Goddard, was selected to manage the project as part of the Pioneer program. Ames, under the direction of Charles F. Hall, was chosen because of its experience with spin-stabilized spacecraft. The mission required a small, lightweight, magnetically clean spacecraft capable of operating in interplanetary space, and its design incorporated hardware previously proven on Pioneer 6 through Pioneer 9. In February 1970, NASA awarded TRW Inc. a US$380 million contract to build both spacecraft without a competitive bidding process in order to meet the mission schedule. B. J. O'Brien and Herb Lassen led the team responsible for assembling the spacecraft. Their design and construction required an estimated 25 million man-hours. One TRW engineer joked, "This spacecraft is guaranteed for two years of interplanetary flight. If any component fails within that warranty period, just return the spacecraft to our shop and we will repair it free of charge." To meet the original schedule, the first spacecraft would have had to launch between February 29 and March 17 to reach Jupiter in November 1974. The launch plan was later revised to target an arrival in December 1973, avoiding conflicts with other missions using the Deep Space Network and the period when Earth and Jupiter would be on opposite sides of the Sun. Pioneer 10's flyby trajectory was chosen to maximize scientific observations of Jupiter's radiation environment, even though mission planners expected some spacecraft systems to be damaged by the intense radiation. The planned closest approach, about three Jupiter radii from the planet's center, was considered the minimum safe distance that would still allow the spacecraft to survive the encounter while providing an unobstructed view of the sunlit hemisphere. A backup spacecraft, Pioneer H, is on display in the "Milestones of Flight" gallery at the National Air and Space Museum. Many aspects of the Pioneer 10 mission informed the planning and design of the Voyager program.
Spacecraft design
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