Pioneer 10

Pioneer 10

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Pioneer 10 is a 258-kilogram robotic
Robotic spacecraft
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 space probe
Space probe
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 that completed the first interplanetary mission to Jupiter, and became the first spacecraft to achieve escape velocity
Escape velocity
In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...

 from the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

. The project was managed by the NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 Ames Research Center and the contract for the construction of the spacecraft was awarded to TRW
TRW
TRW Inc. was an American corporation involved in a variety of businesses, mainly aerospace, automotive, and credit reporting. It was a pioneer in multiple fields including electronic components, integrated circuits, computers, software and systems engineering. TRW built many spacecraft,...

 Inc. The spacecraft was assembled around a hexagonal bus
Satellite bus
A satellite bus or spacecraft bus is the general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of a spacecraft, usually providing locations for the payload .They are most commonly used for geosynchronous satellites, particularly...

 with a 2.74 m parabolic dish high-gain antenna oriented along the spin axis. Power was supplied by four radioisotope thermoelectric generators that provided a combined 155 W at the start of the mission.

Pioneer 10 was launched on March 2, 1972 by an Atlas-Centaur
Atlas-Centaur
The Atlas-Centaur was an American expendable launch system designed and built by General Dynamics Convair Division in San Diego, CA. It was derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was used for 61 orbital launches between 1962 and 1983. It was...

 expendable vehicle from Cape Canaveral, Florida. Between July 15, 1972, and February 15, 1973, it became the first spacecraft to traverse the asteroid belt. Imaging of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

 began November 6, 1973, at a range of 25 million km, and a total of more than 500 images were transmitted. The closest approach to the planet was on December 4, 1973, at a range of 132,252 km. During the mission, the on-board instruments were used to study the asteroid belt, the environment around Jupiter, solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

, cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

s, and eventually the far reaches of the solar system and heliosphere
Heliosphere
The heliosphere is a bubble in space "blown" into the interstellar medium by the solar wind. Although electrically neutral atoms from interstellar volume can penetrate this bubble, virtually all of the material in the heliosphere emanates from the Sun itself...

. Communication has been lost since January 23, 2003 because of power constraints, with the probe at a distance of 12 billion-kilometers (80 AU) from Earth.

History



In the 1960s, American aerospace engineer Gary Flandro
Gary Flandro
Gary Flandro, PhD is an American aerospace engineer who currently holds the Boling Chair of Excellence in Space Propulsion at the University of Tennessee Space Institute. He is also the Vice President and Chief Engineer at Gloyer-Taylor Laboratories . Flandro is an 11th generation pupil of Euler...

 of the NASA Jet Propulsion Laboratory
Jet Propulsion Laboratory
Jet Propulsion Laboratory is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. The facility is headquartered in the city of Pasadena on the border of La Cañada Flintridge and Pasadena...

 conceived of a mission, known as the Planetary Grand Tour
Planetary Grand Tour
The Planetary Grand Tour was an ambitious plan to send unmanned probes to the planets of the outer solar system. Conceived by Gary Flandro of the Jet Propulsion Laboratory in the late 1960s, the Grand Tour would have exploited the alignment of Jupiter, Saturn, Uranus, Neptune, and Pluto, an event...

, that would exploit a rare alignment of the outer planets of the Solar System
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

. To prepare for this mission, in 1964 NASA decided to launch 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. Goddard
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...

 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
Pioneer 11
Pioneer 11 is a 259-kilogram robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind, cosmic rays, and eventually the far reaches of the solar system and heliosphere...

. They formed part of the Pioneer program
Pioneer program
The Pioneer program is a series of United States unmanned space missions that was designed for planetary exploration. There were a number of such missions in the program, but the most notable were Pioneer 10 and Pioneer 11, which explored the outer planets and left the solar system...

, 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 this mission. 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
Polarimetry
Polarimetry is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves...

 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
Zodiacal light
Zodiacal light is a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic or zodiac. Caused by sunlight scattered by space dust in the zodiacal cloud, it is so faint that either moonlight or light pollution renders...

.

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
NASA Ames Research Center
The Ames Research Center , is one of the United States of America's National Aeronautics and Space Administration 10 major field centers.The centre is located in Moffett Field in California's Silicon Valley, near the high-tech companies, entrepreneurial ventures, universities, and other...

, rather than Goddard, was selected to manage the project as part of the Pioneer program
Pioneer program
The Pioneer program is a series of United States unmanned space missions that was designed for planetary exploration. There were a number of such missions in the program, but the most notable were Pioneer 10 and Pioneer 11, which explored the outer planets and left the solar system...

. Ames, under the management of Charles F. Hall, was chosen because of their previous experience with spin-stabilized spacecraft. The requirements called for a small, lightweight spacecraft that was magnetically clean and could perform an interplanetary mission. It was to use spacecraft modules that had already been proven in the Pioneer 6 through 9 missions.

In February 1970, Ames awarded a combined $380 million contract to TRW
TRW
TRW Inc. was an American corporation involved in a variety of businesses, mainly aerospace, automotive, and credit reporting. It was a pioneer in multiple fields including electronic components, integrated circuits, computers, software and systems engineering. TRW built many spacecraft,...

 for building both the Pioneer 10 and Pioneer 11 vehicles, bypassing the 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 person-hours.

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
Deep Space Network
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...

 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 deep and with six 76-centimeters 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 lies within an aluminium honeycomb structure to provide protection from meteoroids. A layer of insulation, consisting of aluminized mylar and kapton
Kapton
Kapton is a polyimide film developed by DuPont which can remain stable in a wide range of temperatures, from -273 to +400 °C...

 blankets, provides passive thermal control. Heat is generated by the dissipation of 70 to 120 watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

s (W) from the electrical components inside the compartment. The heat range is maintained within the operating limits of the equipment by means of louvers located below the mounting platform. The spacecraft had a launch mass of 260-kilograms.

At launch, the spacecraft carried 36 kg of liquid hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...

 monopropellant
Monopropellant rocket
A monopropellant rocket is a rocket that uses a single chemical as its propellant.-Chemical-reaction monopropellant rockets:...

 in a 42 cm diameter spherical tank. Orientation of the spacecraft was 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 last pair were fired in precise coordination with the rotation of the spacecraft in order to precess the rotation axis to the required direction. Orientation information was provided by a star sensor able to reference Canopus
Canopus
Canopus |Alpha]] Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.Canopus is a supergiant of spectral...

, and two sun sensors.

Power and communications



Pioneer 10 used four SNAP-19 radioisotope thermoelectric generator
Radioisotope thermoelectric generator
A radioisotope thermoelectric generator is an electrical generator that obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples.RTGs can be...

s (RTG). They were positioned on 2 three-rod trusses, each 3 meters (10 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. The generators were powered by the radioisotope fuel plutonium-238
Plutonium-238
-External links:**...

, which was 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
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

 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
Thermocouple
A thermocouple is a device consisting of two different conductors that produce a voltage proportional to a temperature difference between either end of the pair of conductors. Thermocouples are a widely used type of temperature sensor for measurement and control and can also be used to convert a...

 junctions led to a more rapid decay in electrical power generation, and by 2005 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 transceiver
Transceiver
A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...

s, one attached to the narrow-beam, high-gain antenna
High-gain antenna
A high-gain antenna is an antenna with a focused, narrow radiowave beam width. This narrow beam width allows more precise targeting of the radio signal - also known as a directional antenna...

, the other to an omni-antenna and medium-gain antenna. The parabolic dish for the high-gain antenna is 2.74 m in diameter and made from an aluminium honeycomb sandwich material. The spacecraft is spun about an axis that is parallel to the axis of this antenna so that it can remain oriented toward the Earth. Each transceiver is 8 W 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
Deep Space Network
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...

 tracking the signal. Data to be transmitted was passed through a convolutional encoder so that most communication errors could be corrected
Error detection and correction
In information theory and coding theory with applications in computer science and telecommunication, error detection and correction or error control are techniques that enable reliable delivery of digital data over unreliable communication channels...

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

Scientific instruments

Helium Vector Magnetometer
Magnetometer
A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...

 (HVM)

This instrument measures the fine structure of the interplanetary magnetic field, maps the Jovian magnetic field, and provides magnetic field measurements to evaluate solar wind interaction with Jupiter. The magnetometer consists of a helium-filled cell mounted on a 6.6–m boom to partly isolate the instrument from the spacecraft's magnetic field.
  • Principal investigator: Edward Smith / JPL
  • Data: PDS/PPI data catalog, [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/mag/ NSSDC data archive]

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Quadrispherical Plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...

 Analyzer

Peers through a hole in the large dish-shaped antenna to detect particles of the solar wind originating from the Sun.
  • Principal investigator: Aaron Barnes / NASA Ames Research Center (archived website)
  • Data: PDS/PPI data catalog, [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/plasma/ NSSDC data archive]

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Charged Particle
Charged particle
In physics, a charged particle is a particle with an electric charge. It may be either a subatomic particle or an ion. A collection of charged particles, or even a gas containing a proportion of charged particles, is called a plasma, which is called the fourth state of matter because its...

 Instrument (CPI)

Detects cosmic rays in the Solar System.
  • Principal investigator: John Simpson / University of Chicago
  • Data: [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/particle/cpi/ NSSDC data archive]

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Cosmic Ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

 Telescope (CRT)

Collects data on the composition of the cosmic ray particles and their energy ranges.
  • Principal investigator: Frank McDonald / NASA Goddard Space Flight Center
  • Data: PDS/PPI data catalog, [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/particle/crt/ NSSDC data archive]

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Geiger Tube Telescope
Geiger tube telescope
The Geiger Tube Telescope is a scientific instrument that measures the intensities, energy spectra, and angular distribution of energetic electrons and protons in interplanetary space and near Jupiter and Saturn....

 (GTT)

Surveys the intensities, energy spectra, and angular distributions of electrons and protons along the spacecraft's path through the radiation belts of Jupiter.
  • Principal investigator: James Van Allen / University of Iowa (website)
  • Data: PDS/PPI data catalog, [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/particle/gtt/ NSSDC data archive]

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Trapped Radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 Detector (TRD)

Includes an unfocused Cerenkov counter that detects the light emitted in a particular direction as particles pass through it recording electrons of energy, 0.5 to 12 MeV, an electron scatter detector for electrons of energy, 100 to 400 keV, and a minimum ionizing detector consisting of a solid-state diode that measures minimum ionizing particles (<3 MeV) and protons in the range of 50 to 350 MeV.
  • Principal investigator: R. Fillius / University of California San Diego
  • Data: [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/particle/trd/ NSSDC data archive]

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Meteoroid
Meteoroid
A meteoroid is a sand- to boulder-sized particle of debris in the Solar System. The visible path of a meteoroid that enters Earth's atmosphere is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite...

 Detectors

Twelve panels of pressurized cell detectors mounted on the back of the main dish antenna record penetrating impacts of small meteoroids.

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Asteroid/Meteoroid Detector (AMD)

Meteoroid-asteroid detector looks into space with four non-imaging telescopes to track particles ranging from close-by bits of dust to distant large asteroids.
  • Principal investigator: Robert Soberman / General Electric Company
  • Data: [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/asteroid_meteoroid_astronomy/ NSSDC data archive]

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Ultraviolet Photometer
Photometer
In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...


Ultraviolet light is sensed to determine the quantities of hydrogen and helium in space and on Jupiter.
  • Principal investigator: Darrell Judge / University of Southern California
  • Data: PDS/PPI data catalog, [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/pioneer/pioneer10/uv/ NSSDC data archive]

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Imaging Photopolarimeter
Polarimeter
A polarimeter is a scientific instrument used to measure the angle of rotation caused by passing polarized light through an optically active substance....

 (IPP)

The imaging experiment relies upon the spin of the spacecraft to sweep a small telescope across the planet in narrow strips only 0.03 degrees wide, looking at the planet in red and blue light. These strips were then processed to build up a visual image of the planet.

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Infrared Radiometer
Radiometer
A radiometer is a device for measuring the radiant flux of electromagnetic radiation. Generally, the term radiometer denotes an infrared radiation detector, yet it also includes detectors operating on any electromagnetic wavelength....


Provides information on cloud temperature and the output of heat from Jupiter.
  • Principal investigator: Andrew Ingersoll / California Institute of Technology

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Pioneer plaque


At the behest of Carl Sagan
Carl Sagan
Carl Edward Sagan was an American astronomer, astrophysicist, cosmologist, author, science popularizer and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books...

, Pioneer 10 and Pioneer 11 carry a 152 millimetre gold-anodized aluminium plaque
Commemorative plaque
A commemorative plaque, or simply plaque, is a plate of metal, ceramic, stone, wood, or other material, typically attached to a wall, stone, or other vertical surface, and bearing text in memory of an important figure or event...

 in case either spacecraft is ever found by intelligent life-forms from another planetary system. The plaques feature the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft. The plaque is attached to the antenna support struts to provide some shielding from interstellar dust.

Launch and trajectory


The Pioneer 10 probe was launched on March 3, 1972 at 01:49:00 UTC (March 2 local time) by the National Aeronautics and Space Administration from Space Launch Complex 36A at Cape Canaveral
Cape Canaveral Air Force Station
Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...

, Florida aboard an Atlas/Centaur
Atlas-Centaur
The Atlas-Centaur was an American expendable launch system designed and built by General Dynamics Convair Division in San Diego, CA. It was derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was used for 61 orbital launches between 1962 and 1983. It was...

 launch vehicle. The third stage consisted of a solid fuel TE364-4 developed specifically for the Pioneer missions. This stage provided about 15,000 pounds of thrust and spun up the spacecraft. The spacecraft had an initial spin rate of 30 revolutions per minute. Twenty minutes following the launch, the vehicle's three booms were extended, which slowed the rotation rate to 4.8 per minute. This rate was maintained throughout the voyage. The launch vehicle accelerated the probe for net interval of 17 minutes, reaching a velocity of 51,682 kilometers/hour (32,114 miles/hour).

After the high-gain antenna was contacted, several of the instruments were activated for testing while Pioneer 10 was moving through the Earth's radiation belts. Ninety minutes after launch, the spacecraft reached interplanetary space. Pioneer 10 passed by the Moon in 11 hours and become the fastest man-made object at that time. Two days after launch, the scientific instruments were turned on, beginning with the cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...

 telescope. After ten days, all of the instruments were active.

During the first seven months of the journey, the spacecraft made three course corrections. The on-board instruments underwent checkouts, with the photometer
Photometer
In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...

s examining Jupiter and the Zodiacal light
Zodiacal light
Zodiacal light is a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic or zodiac. Caused by sunlight scattered by space dust in the zodiacal cloud, it is so faint that either moonlight or light pollution renders...

, and experiment packages being used to measure cosmic rays, magnetic fields and the solar wind. The only anomaly during this interval was the failure of the star sensor, which instead required the spacecraft to maintain its orientation using the two sun sensors.

While passing through interplanetary space, Pioneer 10 became the first mission to detect interplanetary atoms of helium. It also observed high-energy ions of aluminium and sodium in the solar wind. On July 15, 1972, Pioneer 10 was the first spacecraft to enter the asteroid belt, located between the orbits of Mars and Jupiter. The project planners expected a safe passage through the belt, and the closest the trajectory would take Pioneer 10 to any of the known asteroids was . One of the nearest approaches was to the asteroid 307 Nike on December 2, 1972.

The on-board experiments demonstrated a deficiency of particles below a micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

 (μm) in the belt, as compared to the vicinity of the Earth. The density of dust particles between 10–100 μm did not vary significantly during the trip from the Earth to the outer edge of the belt. Only for particles with a diameter of 100 μm to 1.0 mm did the density show an increase, by a factor of three-fold in the region of the belt. No fragments larger than a millimetre were observed in the belt, indicating these are likely rare; certainly much less common than anticipated. As the spacecraft did not collide with any particles of substantial size, it passed safely through the belt, emerging on the other side about February 15, 1973.

Encounter with Jupiter


On November 6, 1973, the Pioneer 10 spacecraft was at a distance of 25 million km from Jupiter. Testing of the imaging system began, and the data was successfully received back at the Deep Space Network
Deep Space Network
The Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...

. A series of 16,000 commands were then uploaded to the spacecraft to control the fly-by operations during next 60 days. The orbit of the outer moon Sinope was crossed on November 8. The bow shock of Jupiter's magnetosphere was reached on November 16, as indicated by a drop in the velocity of the solar wind from 451 km/s to 225 km/s. The magnetopause was passed through a day later. The spacecraft instruments confirmed that the magnetic field of Jupiter was inverted compared to that of Earth. By the 29th, the orbits of all of the outermost moons had been passed and the spacecraft was operating flawlessly.

Red and blue pictures of Jupiter were being generated by the imaging photopolarimeter as the rotation of the spacecraft carried the instrument's field of view past the planet. These red and blue colors were combined to produce a synthetic green image, allowing a three-color combination to produce the rendered image. On November 26, a total of twelve such images were received back on Earth. By December 2, the image quality exceeded the best images made from Earth. These were being displayed in real-time back on Earth, and the Pioneer Program would later receive an Emmy award for this presentation to the media. The motion of the spacecraft produced geometric distortions that later had to be corrected by computer processing. During the encounter, a total of more than 500 images were transmitted.

The trajectory of the spacecraft took it along the magnetic equator of Jupiter, where the ion radiation was concentrated. Peak intensities for these electrons 10,000 times stronger than the maximum around Earth. Starting on December 3, the radiation around Jupiter caused false commands to be generated. Most of these were corrected by contingency commands, but the Io image and a few close ups of Jupiter were lost. Similar false commands would be generated on the way out from the planet.
Nonetheless, Pioneer 10 did succeed in obtaining images of the moons Ganymede and Europa. The image of Ganymede showed low albedo features in the center and near the south pole, while the north pole appeared brighter. Europa was too far away to obtain a detailed image, although some albedo features were apparent.

The trajectory of Pioneer 10 was chosen to take it behind Io, allowing the refractive effect of the moon's atmosphere on the radio transmissions to be measured. This demonstrated that the ionosphere of the moon was about 700 km above the surface on the day side, and the density ranged from 60,000 electrons per cubic centimeter on the day side, down to 9,000 on the night face. An unexpected discovery was that Io was orbiting within a cloud of hydrogen that extended for about 805,000 km, with a width and height of 402,000 km. A smaller, 110,000 km cloud was believed to have been detected about Europa.

At the closest approach, the velocity of the spacecraft reached 132,000 km/hr. The spacecraft came within 132,252 km of the outer atmosphere of Jupiter. Close-in images of the Great Red Spot and the terminator were obtained. Communication with the spacecraft then ceased as it passed behind the planet. The occultation data allowed the temperature structure of the outer atmosphere to be measured, showing a temperature inversion between the altitudes with 10 and 100 mbar pressures. Temperatures at the 10 mbar level ranged from -133° to -113°C, while temperatures at the 100 mbar level were -183° to -163°C. The spacecraft generated an infrared map of the planet, which confirmed the idea that the planet radiated more heat than it received from the Sun.

Crescent images of the planet were then returned as Pioneer 10 moved away from the planet. As the spacecraft headed outward, it again passed the bow shock of Jupiter's magnetosphere. As this front is constantly shifting in space because of dynamic interaction with the solar wind, the vehicle crossed the bow shock a total of 17 times before it escaped completely.

Deep space


Pioneer 10 crossed the orbit of Saturn in 1976 and the orbit of Uranus in 1979. The mission came to an official end on March 31, 1997, when it had reached a distance of 67 AU from the Sun, though the spacecraft was still able to transmit coherent data after this date.

Analysis of the radio tracking data from the Pioneer 10 and 11
Pioneer 11
Pioneer 11 is a 259-kilogram robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind, cosmic rays, and eventually the far reaches of the solar system and heliosphere...

 spacecraft at distances between 20–70 AU from the Sun has consistently indicated the presence of a small but anomalous Doppler
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...

 frequency drift. The drift can be interpreted as due to a constant acceleration of directed towards the Sun. Although it is suspected that there is a systematic origin to the effect, none has been found. As a result, there is sustained interest in the nature of this so-called "Pioneer anomaly
Pioneer anomaly
The Pioneer anomaly or Pioneer effect is the observed deviation from predicted accelerations of the Pioneer 10 and Pioneer 11 spacecraft after they passed about on their trajectories out of the Solar System....

".

After March 31, 1997, Pioneer 10s weak signal continued to be tracked by the Deep Space Network to aid the training of flight controllers in the process of acquiring deep space radio signals. There was an Advanced Concepts
NASA Institute for Advanced Concepts
right|200pxNASA Institute for Advanced Concepts was a NASA-funded program that was operated by the Universities Space Research Association for NASA from 1998 until its closure on 31 August 2007. NIAC sought proposals for revolutionary aeronautics and space concepts that could dramatically impact...

 study applying chaos theory
Chaos theory
Chaos theory is a field of study in mathematics, with applications in several disciplines including physics, economics, biology, and philosophy. Chaos theory studies the behavior of dynamical systems that are highly sensitive to initial conditions, an effect which is popularly referred to as the...

 to extract coherent data from the fading signal.

The last successful reception of telemetry
Telemetry
Telemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...

 was received from Pioneer 10 on April 27, 2002; subsequent signals were barely strong enough to detect, and provided no usable data. The final, very weak signal from Pioneer 10 was received on January 23, 2003 when it was 12 billion-kilometers (80 AU) from Earth. Further attempts to contact the spacecraft were unsuccessful. The final attempt was made on the evening of March 4, 2006, the last time the antenna would be correctly aligned with Earth. No response was received from Pioneer 10. NASA decided that the RTG units had probably fallen below the power threshold needed to operate the transmitter. Hence, no further attempts at contact were made.

Timeline

Timeline of travel
EWLINE
Date Event
Spacecraft launched
Crossed orbit of Mars.
Entered the asteroid belt.
Start Jupiter observation phase.
Begin Pioneer Interstellar Mission.

Legacy


The velocity away from the Sun is now a steady 12.2 km/s, or approximately 2.6 AU per year, which is sufficient to escape the Solar System. If left undisturbed, Pioneer 10 will join the Voyager Spacecraft and will leave the solar system to wander interstellar space. The trajectory into interstellar space
Interstellar Space
Interstellar Space was one of the final studio albums recorded by the saxophonist John Coltrane before his death in 1967, originally-released posthumously by Impulse! Records on LP in 1974.-Composition:...

 is expected to take it in the general direction of the star Aldebaran
Aldebaran
Aldebaran is a red giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky...

, currently located at a distance of about 68 light years. If Aldebaran had zero relative velocity
Relative velocity
In non-relativistic kinematics, relative velocity is the vector difference between the velocities of two objects, as evaluated in terms of a single coordinate system....

, it would require more than 2 million years for the spacecraft to reach the star.

A backup unit, Pioneer H
Pioneer H
Pioneer H is an unlaunched unmanned space mission that was part of the US Pioneer program for a planned 1974 launch. Had this mission and spacecraft been launched, it would have been designated Pioneer 12; that designation was later applied to the Pioneer Venus Orbiter.The probe would have been...

, is currently on display in the "Milestones of Flight" exhibit at the National Air and Space Museum
National Air and Space Museum
The National Air and Space Museum of the Smithsonian Institution holds the largest collection of historic aircraft and spacecraft in the world. It was established in 1976. Located in Washington, D.C., United States, it is a center for research into the history and science of aviation and...

 in Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

. Many elements of the mission proved to be critical in the planning of the Voyager program
Voyager program
The Voyager program is a U.S program that launched two unmanned space missions, scientific probes Voyager 1 and Voyager 2. They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s...

.

See also


  • Exploration of Jupiter
    Exploration of Jupiter
    The exploration of Jupiter has to date been conducted via close observations by automated spacecraft. It began with the arrival of Pioneer 10 into the Jovian system in 1973, and, , has continued with seven further spacecraft missions...

  • Cassini probe
  • S band
    S band
    The S band is defined by an IEEE standard for radio waves with frequencies that range from 2 to 4 GHz, crossing the conventional boundary between UHF and SHF at 3.0 GHz. It is part of the microwave band of the electromagnetic spectrum...

  • Unmanned space missions

External links