Picture of Pioneer SpacecraftThe Pioneer 10 & 11 Spacecraft

This is an artist's drawing of one of the twin Pioneer spacecraft.

This page was last revised 7 February 2003.

The Pioneers are managed by the Ames Research Center, Mountain View, Calif., for NASA's Office of Space Science. The spacecraft were built by TRW Space & Technology Group, Redondo Beach, Calif. under contract with NASA, Ames Research Center.

Mission History

Pioneer 10 was launched on 2 March 1972 on top of an Atlas/Centaur/TE364-4 launch vehicle. The launch marked the first use of the Atlas-Centaur as a three-stage launch vehicle. The third stage was required to rocket Pioneer 10 to the speed of 51,810 kilometers per hour (32,400 mph) needed for the flight to Jupiter. This made Pioneer the fastest manmade object to leave the Earth, fast enough to pass the Moon in 11 hours and to cross the Mars orbit, about 80 million kilometers (50 million miles) away, in just 12 weeks.

On 15 July 1972 Pioneer 10 entered the Asteroid Belt, a doughnut shaped area which measures some 280 million kilometers wide and 80 million kilometers thick. The material in the belts travels at speed about 20 km/sec. and ranges in size from dust particles to rock chunks as big as Alaska.

After safely traversing the Asteroid Belt, Pioneer 10 headed toward Jupiter. Accelerated by the massive giant to a speed of 132,000 km/hr (82,000 mph), Pioneer 10 passed by Jupiter within 130,354 km (81,000 miles) of the cloudtops on December 3, 1973. During the passage by Jupiter, Pioneer 10 obtained the first close-up images of the planet, charted Jupiter's intense radiation belts, located the planet's magnetic field, and discovered that Jupiter is predominantly a liquid planet.

Following its encounter with Jupiter, Pioneer 10 explored the outer regions of the Solar system, studying energetic particles from the �Sun (Solar Wind), and cosmic rays entering our portion of the Milky Way. The spacecraft continued to make valuable scientific investigations in the outer regions of the solar system until its science mission ended on March 31, 1997. Since that time, Pioneer 10�s weak signal has been tracked by the DSN as part of an advanced concept study of communication technology in support of NASA's future interstellar probe mission. The spacecraft had also been used to help train flight controllers how to acquire radio signals from space during the Lunar Prospector mission. The power source on Pioneer 10 finally degraded to the point where the signal to Earth dropped below the threshold for detection in its latest contact attempt on 7 February, 2003. The previous three contacts had very faint signals with no telemetry received. The last time a Pioneer 10 contact returned telemetry data was on 27 April 2002.

Pioneer 11 was launched on 5 April 1973, like Pioneer 10, on top of an Atlas/Centaur/TE364-4 launch vehicle. After safe passage through the Asteroid belt on 19 April 1974, the Pioneer 11 thrusters were fired to add another 63.7 m/sec (210 ft/sec) to the spacecraft's velocity. This adjusted the aiming point at Jupiter to 43,000 km (26,725 miles) above the cloudtops. The close approach also allowed the spacecraft to be accelerated by Jupiter to a velocity 55 times that of the muzzle velocity of a high speed rifle bullet - 173,000 km/hr (108,000 mph) - so that it would be carried across the Solar System some 2.4 billion kilometers (1.5 billion miles) to Saturn.

During its flyby of Jupiter on 2 December 1974, Pioneer 11 obtained dramatic images of the Great Red Spot, made the first observation of the immense polar regions, and determined the mass of Jupiter's moon, Callisto.

Looping high above the ecliptic plane and across the Solar System, Pioneer 11 raced toward its appointment with Saturn on 1 September 1979. Pioneer 11 flew to within 13,000 miles of Saturn and took the first close-up pictures of the planet. Instruments located two previously undiscovered small moons and an additional ring, charted Saturn's magnetosphere and magnetic field and found its planet-size moon, Titan, to be too cold for life. Hurtling underneath the ring plane, Pioneer 11 sent back amazing pictures of Saturn's rings. The rings, which normally seem bright when observed from Earth, appeared dark in the Pioneer pictures, and the dark gaps in the rings seen from Earth appeared as bright rings.

Following its encounter with Saturn, Pioneer 11 explored the outer regions of our Solar system, studying energetic particles from our Sun (Solar Wind) and cosmic rays entering our portion of the Milky Way. In September 1995, Pioneer 11 was at a distance of 6.5 billion km (4 billion miles) from Earth. At that distance, it takes over 6 hours for the radio signal (which is traveling at the speed of light) to reach Earth. However, by September 1995, Pioneer 11 could no longer make any scientific observations. On 30 September 1995, routine daily mission operations were stopped. Intermittent contact continued until November 1995, at which time the last communication with Pioneer 11 took place. There have been no communications with Pioneer 11 since. The Earth's motion has carried it out of the view of the spacecraft antenna. The spacecraft cannot be maneuvered to point back at the Earth. It is not known whether the spacecraft is still transmitting a signal. No further tracks of Pioneer 11 are scheduled.

Description of the Spacecraft

Measured from its farthest ends, from the horn of the medium-gain antenna to the tip of the omnidirectional antenna, the Pioneer spacecraft is 2.9 meters (9 1/2 feet) long. Its widest cross-wise dimension, exclusive of the booms, is the 2.7-meter (9-foot) diameter high gain antenna. Pioneer weighs 270 kilograms (570 pounds). The spacecraft is spin-stabilized, spinning about the axis of the high gain dish antenna at approximately 5 rpm. Six Hydrazine thrusters provide velocity, attitude and spin-rate control.

Electrical power is provided by four radioisotope thermoelectric generators (RTG), each providing 40 watts of power at launch. Two three-rod trusses, 120 degrees apart, project from the equipment compartment to deploy the RTG power sources about 10 feet from the center of the spacecraft. A third boom, 120 degrees from the others, projects from the experiments compartment and positions the helium vector magnetometer sensor 20 feet from the spacecraft center.

Pioneer 10 carries 11 instruments, and Pioneer 11 carries 12.

As the first two spacecraft to leave our solar system, Pioneer 10 & 11 carry a graphic message in the form of a 6- by 9-inch gold anodized plaque bolted to the spacecraft's main frame.

About the Launch Vehicle

Picture of Launch VehicleLaunch of Pioneer 10

The Atlas vehicle has a total thrust of 411,353 pounds, consisting of two 174,841-pound-thrust booster engines; one 60,317-pound thrust sustainer engine, and two vernier engines, each developing 676 pounds thrust. Propellants are liquid oxygen and RP1.

The Centaur second stage has two engines having a total thrust of 29,200 pounds. This engine carries insulation panels which are jettisoned just before the vehicle leaves the Earth's atmosphere and are used to prevent heat or air friction from causing boil-off of liquid hydrogen during flight through the atmosphere. Propellant is liquid hydrogen and liquid oxygen.

The solid-fueled TE364-4 third stage develops approximately 15,000 pounds of thrust. This stage also spins the spacecraft up to 60 rpm.

For further launch information, see NASA Lewis Pioneer 10 Silver Anniversary.

Scientific Instruments

The following is a list of scientific instruments on board the Pioneer 10 & 11 spacecraft. Some instruments eventually failed (F) or were only used during Jupiter or Saturn encounter (ENC).

Pioneer 10 Instruments

Helium Vector Magnetometer (F)

Plasma Analyzer

Charged Particle Instrument

Cosmic Ray Telescope

Geiger Tube Telescope

Trapped Radiation Detector

Meteoroid Detector (ENC)(F)

Asteroid-Meteoroid Experiment (ENC)(F)

Ultraviolet Photometer

Imaging Photopolarimeter (ENC)

Infrared Radiometer (F)

Pioneer 11 Instruments

The Pioneer 11 instruments are the same as the Pioneer 10 instruments, except that a Flux-Gate Magnetometer was added. As the spacecraft power continued to decline, instruments had to be turned off. By October 1995, none of the instruments could be operated, and the scientific investigations by Pioneer 11 came to an end. Sometime in late 1996, its transmitter will fall silent altogether, and Pioneer 11 will travel forever as a ghost ship in our galaxy. See Current Spacecraft Status.

Pioneer Plaque

Picture of Plaque

On the plaque a man and woman stand before an outline of the spacecraft. The man's hand is raised in a gesture of good will. The physical makeup of the man and woman were determined from results of a computerized analysis of the average person in our civilization.

The key to translating the plaque lies in understanding the breakdown of the most common element in the universe - hydrogen. This element is illustrated in the left-hand corner of the plaque in schematic form showing the hyperfine transition of neutral atomic hydrogen. Anyone from a scientifically educated civilization having enough knowledge of hydrogen would be able to translate the message. The plaque was designed by Dr. Carl Sagan and Dr. Frank Drake and drawn by Linda Salzman Sagan.

Return to Pioneer Home Page