Pioneer 10 (originally designated Pioneer F) is an American space probe, launched in 1972 and weighing 258 kilograms (569 pounds), that completed the first mission to the planet Jupiter. Thereafter, Pioneer 10 became the first of five artificial objects to achieve the escape velocity needed to leave the Solar System. This space exploration project was conducted by the NASA Ames Research Center in California, and the space probe was manufactured by TRW Inc.

Pioneer 10 was assembled around a hexagonal bus with a 2.74-meter (9 ft 0 in) diameter parabolic dish high-gain antenna, and the spacecraft was spin stabilized around the axis of the antenna. Its electric power was supplied by four radioisotope thermoelectric generators that provided a combined 155 watts at launch.

It was launched on March 2, 1972, by an Atlas-Centaur expendable vehicle from Cape Canaveral, Florida. Between July 15, 1972, and February 15, 1973, it became the first spacecraft to traverse the asteroid belt. Photography of Jupiter began November 6, 1973, at a range of 25,000,000 kilometers (16,000,000 mi), and about 500 images were transmitted. The closest approach to the planet was on December 4, 1973, at a range of 132,252 kilometers (82,178 mi). During the mission, the on-board instruments were used to study the asteroid belt, the environment around Jupiter, the solar wind, cosmic rays, and eventually the far reaches of the Solar System and heliosphere.

Radio communications were lost with Pioneer 10 on January 23, 2003, because of the loss of electric power for its radio transmitter, with the probe at a distance of 12 billion kilometers (80 AU) from Earth.

Mission background History

In the 1960s, American aerospace engineer Gary Flandro of the NASA Jet Propulsion Laboratory conceived of a mission, known as the Planetary Grand Tour, that would exploit a rare alignment of the outer planets of the Solar System. This mission would ultimately be accomplished in the late 1970s by the two Voyager probes, but in order to prepare for it, NASA decided in 1964 to experiment with launching a pair of probes to the outer Solar System. An advocacy group named the Outer Space Panel and chaired by American space scientist James A. Van Allen, worked out the scientific rationale for exploring the outer planets. NASA Goddard Spaceflight Center put together a proposal for a pair of "Galactic Jupiter Probes" that would pass through the asteroid belt and visit Jupiter. These were to be launched in 1972 and 1973 during favorable windows that occurred only a few weeks every 13 months. Launch during other time intervals would have been more costly in terms of propellant requirements.

Approved by NASA in February 1969, the twin spacecraft were designated Pioneer F and Pioneer G before launch; later they were named Pioneer 10 and Pioneer 11. They formed part of the Pioneer program, a series of United States unmanned space missions launched between 1958 and 1978. This model was the first in the series to be designed for exploring the outer Solar System. Based on multiple proposals issued throughout the 1960s, the early mission objectives were to explore the interplanetary medium past the orbit of Mars, study the asteroid belt and assess the possible hazard to spacecraft traveling through the belt, and explore Jupiter and its environment. Later development-stage objectives included the probe closely approaching Jupiter to provide data on the effect the environmental radiation surrounding Jupiter would have on the spacecraft instruments.

More than 150 scientific experiments were proposed for the missions. The experiments to be carried on the spacecraft were selected in a series of planning sessions during the 1960s, then were finalized by early 1970. These would be to perform imaging and polarimetry of Jupiter and several of its satellites, make infrared and ultraviolet observations of Jupiter, detect asteroids and meteoroids, determine the composition of charged particles, and to measure magnetic fields, plasma, cosmic rays and the zodiacal light. Observation of the spacecraft communications as it passed behind Jupiter would allow measurements of the planetary atmosphere, while tracking data would improve estimates of the mass of Jupiter and its moons.

NASA Ames Research Center, rather than Goddard, was selected to manage the project as part of the Pioneer program. The Ames Research Center, under the direction of Charles F. Hall, was chosen because of its previous experience with spin-stabilized spacecraft. The requirements called for a small, lightweight spacecraft which was magnetically clean and which could perform an interplanetary mission. It was to use spacecraft modules that had already been proven in the Pioneer 6 through 9 missions. Ames commissioned a documentary film by George Van Valkenburg titled "Jupiter Odyssey". It received numerous international awards, and is visible on Van Valkenburg's YouTube channel.

In February 1970, Ames awarded a combined $380 million contract to TRW Inc. for building both of the Pioneer 10 and 11 vehicles, bypassing the usual bidding process to save time. B. J. O'Brien and Herb Lassen led the TRW team that assembled the spacecraft. Design and construction of the spacecraft required an estimated 25 million man-hours. An engineer from TRW said "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 schedule, the first launch would need to take place between February 29 and March 17 so that it could arrive at Jupiter in November 1974. This was later revised to an arrival date of December 1973 in order to avoid conflicts with other missions over the use of the Deep Space Network for communications, and to miss the period when Earth and Jupiter would be at opposite sides of the Sun. The encounter trajectory for Pioneer 10 was selected to maximize the information returned about the radiation environment around Jupiter, even if this caused damage to some systems. It would come within about three times the radius of the planet, which was thought to be the closest it could approach and still survive the radiation. The trajectory chosen would give the spacecraft a good view of the sunlit side.

Spacecraft design

The Pioneer 10 bus measures 36 centimeters (14 in) deep and with six 76-centimeter (30 in) long panels forming the hexagonal structure. The bus houses propellant to control the orientation of the probe and eight of the eleven scientific instruments. The equipment compartment lay within an aluminum honeycomb structure to provide protection from meteoroids. A layer of insulation, consisting of aluminized mylar and kapton blankets, provides passive thermal control. Heat was generated by the dissipation of 70 to 120 watts (W) from the electrical components inside the compartment. The heat range was maintained within the operating limits of the equipment by means of louvers located below the mounting platform. The spacecraft had a launch mass of about 260 kilograms (570 lb).:42

At launch, the spacecraft carried 36 kilograms (79 lb) of liquid hydrazine monopropellant in a 42-centimeter (17 in) diameter spherical tank. Orientation of the spacecraft is maintained with six 4.5 N, hydrazine thrusters mounted in three pairs. Pair one maintained a constant spin-rate of 4.8 rpm, pair two controlled the forward thrust, and pair three controlled the attitude. The attitude pair were used in conical scanning maneuvers to track Earth in its orbit. Orientation information was also provided by a star sensor able to reference Canopus, and two Sun sensors.

Power and communications

Pioneer 10 uses four SNAP-19 radioisotope thermoelectric generators (RTGs). They are positioned on two three-rod trusses, each 3 meters (9.8 ft) in length and 120 degrees apart. This was expected to be a safe distance from the sensitive scientific experiments carried on board. Combined, the RTGs provided 155 W at launch, and decayed to 140 W in transit to Jupiter. The spacecraft required 100 W to power all systems.:44–45 The generators are powered by the radioisotope fuel plutonium-238, which is housed in a multi-layer capsule protected by a graphite heat shield.

The pre-launch requirement for the SNAP-19 was to provide power for two years in space; this was greatly exceeded during the mission. The plutonium-238 has a half-life of 87.74 years, so that after 29 years the radiation being generated by the RTGs was at 80% of its intensity at launch. However, steady deterioration of the thermocouple junctions led to a more rapid decay in electrical power generation, and by 2001 the total power output was 65 W. As a result, later in the mission only selected instruments could be operated at any one time.

The space probe includes a redundant system of transceivers, one attached to the narrow-beam, high-gain antenna, the other to an omni-antenna and medium-gain antenna. The parabolic dish for the high-gain antenna is 2.74 meters (9.0 ft) in diameter and made from an aluminum honeycomb sandwich material. The spacecraft was spun about an axis that is parallel to the axis of this antenna so that it could remain oriented toward the Earth. Each transceiver is an 8 W one and transmits data across the S-band using 2110 MHz for the uplink from Earth and 2292 MHz for the downlink to Earth with the Deep Space Network tracking the signal. Data to be transmitted is passed through a convolutional encoder so that most communication errors could be corrected by the receiving equipment on Earth.:43 The data transmission rate at launch was 256 bit/s, with the rate degrading by about −1.27 millibit/s for each day during the mission.

Much of the computation for the mission is performed on Earth and transmitted to the spacecraft, where it was able to retain in memory up to five commands of the 222 possible entries by ground controllers. The spacecraft includes two command decoders and a command distribution unit, a very limited form of a processor, to direct operations on the spacecraft. This system requires that mission operators prepare commands long in advance of transmitting them to the probe. A data storage unit is included to record up to 6,144 bytes of information gathered by the instruments. The digital telemetry unit is used to prepare the collected data in one of the thirteen possible formats before transmitting it back to Earth.:38

At the CHM celebration of the 35th anniversary of the intel 4004 microprocessor on November 13 2006 Federico Faggin said the 4004 processor was one of the artefacts aboard Pioneer 10. (Wikipedia)