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Pioneers (1958-2003) Pioneer | Mariner | Viking | Voyager | Magellan | Pathfinder | Galileo | Mars Global Surveyor
Overview Almost everyone has heard of Pioneer 10 and 11, the two spacecraft that were the first to visit the outer solar system. But very few people have ever known that there were earlier and later Pioneer craft that visited the inner solar system. There were over a dozen Pioneer missions, and they helped scientists to learn more about spacecraft operations and the environments of interplanetary space. The Terran and Lunar Pioneers Pioneer 0
This spacecraft was the first U.S. attempt at a lunar mission. The Pioneer 0 probe was designed to go into orbit around the moon and carried a TV camera and other instruments as part of the first International Geophysical Year (IGY) science payload. The spacecraft was destroyed by an explosion of the first (Thor booster) stage 77 seconds after launch at 16 km altitude, 16 km downrange over the Atlantic. Failure was suspected to be due to a ruptured fuel or oxygen line. Erratic telemetry signals were received from the payload and upper stages for 123 seconds after the explosion, and the upper stages were tracked to impact in the ocean. Pioneer 1
The error that caused the craft not to reach the moon was due to a programming error in the upper stage that caused a slight error in burnout velocity and angle (3.5°). This resulted in a ballistic trajectory with a peak altitude of 113,800 km around 13:00 local time. The real-time transmission was obtained for about 75% of the flight, but the percentage of data recorded for each experiment was variable. Except for the first hour of flight, the signal to noise ratio was good. The spacecraft ended transmission when it reentered Earth's atmosphere after 43 hours of flight on October 13, 1958, at 03:46 UT over the South Pacific Ocean. A small quantity of useful scientific information was returned, showing the radiation surrounding Earth was in the form of bands, measuring the extent of the bands, mapping the total ionizing flux, making the first observations of hydromagnetic oscillations of the magnetic field, and taking the first measurements of the density of micrometeorites and the interplanetary magnetic field. Pioneer 2
Pioneer 2 was the last of the three project Able space probes designed to probe lunar and cislunar space, and it was identical in design to Pioneer 1. Shortly after launch, the third stage of the launch vehicle separated but failed to ignite, and Pioneer 2 did not achieve its intended lunar orbit. The craft attained a maximum altitude of 1550 km before reentering Earth's atmosphere at 28.7° N, 1.9° E over NW Africa. A small amount of data was obtained during the short flight, including evidence that the equatorial region around Earth has higher flux and higher energy radiation than previously considered and that the micrometeorite density is higher around Earth than in space. Pioneer 3
The flight plan called for the Pioneer 3 probe to pass close to the moon after 33.75 hours and then go into solar orbit. However, depletion of propellant caused the first stage engine to shut down 3.7 seconds early preventing the spacecraft from reaching escape velocity. The injection angle was also about 71°instead of the planned 68°. The probe reentered Earth's atmosphere and burned up over Africa on December 7 at approximately 19:51 UT at an estimated location of 16.4° N, 18.6° E. The probe returned telemetry for about 25 hours of its 38 hour 6 minute journey. The other 13 hours were blackout periods due to the location of the two tracking stations. The returned information showed that the internal temperature remained at about 43 °C over most of the period. The data obtained were of particular value since they indicated the existence of two distinct radiation belts. Pioneer 4
Pioneer 4 was the first American spacecraft to escape Earth's gravitational pull as it passed within 58,983 km (36,650 miles) of the moon on March 4 at 22:25 UT at a speed of 7230 km/hr. The spacecraft returned data on the moon's radiation environment, although the desire to be the first man-made vehicle to fly past the moon was lost when the Soviet Union's Luna 1 passed by the moon several weeks before Pioneer 4. Pioneer 4 was a spin stabilized spacecraft launched on a lunar flyby trajectory and into a heliocentric orbit. It carried a payload similar to Pioneer 3: A lunar radiation environment experiment using a Geiger-Mueller tube detector and a lunar photography experiment. Despite how close it came to the moon, Pioneer 4 did not come close enough to trigger the photoelectric sensor. No lunar radiation was detected. The probe was tracked for 82 hours to a distance of 655,000 km and reached perihelion on March 18, 1959 at 01:00 UT. The cylindrical fourth stage casing (173 cm long, 15 cm diameter, 4.65 kg) went into orbit with the probe. The spacecraft was still in solar orbit as of 1969. Pioneer P-3
The spacecraft was launched on an Air Force-Convair Atlas intercontinental ballistic missile coupled to Thor-Able upper stages including an Able x 248 rocket third stage. The plastic payload shroud broke away 45 seconds after launch, subjecting the payload and third stage rocket to critical aerodynamic loads. At 104 seconds after launch, communications with the upper stages was lost and the payload was stripped off followed by the third stage. Telemetry indicated the first and second stages continued as programmed. Pioneer 5
Pioneer 5 was a spin-stabilized space probe used to investigate interplanetary space between the orbits of Earth and Venus. The spacecraft measured magnetic field phenomena, solar flare particles, and ionization in the interplanetary region. The digital data were transmitted at 1, 8, and 64 bps, depending on the distance of the spacecraft from Earth and the size of the receiving antenna. Weight limitations on the solar cells prevented continuous operation of the telemetry transmitters. About four operations of 25 minutes duration were scheduled per day with occasional increases during times of special interest. A total of 138.9 hours of operation was completed, and over 3 million binary bits of data were received. The major portion of the data was received at the Manchester and Hawaii tracking stations because their antennas provided grid reception. Pioneer 5 performed normally until April 30, 1960, after which telemetry transmission became too infrequent for any significant addition to the data. The spacecraft established a communications link with Earth from a record distance of 22.5 million miles on June 26, 1960, which was the last day of transmission. Pioneer P-30
Pioneer P-30 was intended to be a lunar orbiter probe, but the mission failed shortly after launch. The objectives were to place a highly instrumented probe in lunar orbit, to investigate the environment between the Earth and Moon, and to develop technology for controlling and maneuvering spacecraft from Earth. It was equipped to estimate the moon's mass and topography of the poles, record the distribution and velocity of micrometeorites, and study radiation, magnetic fields, and low frequency electromagnetic waves in space. A mid-course propulsion system and injection rocket would have been the first U.S. self-contained propulsion system capable of operation many months after launch at great distances from Earth and the first U.S. tests of maneuvering a satellite in space. The spacecraft was launched on an Air Force-Convair Atlas D intercontinental ballistic missile coupled to Thor-Able upper stages including a Hercules ABL solid propellant third stage. The first stage burned normally for 275 seconds, the two Atlas booster engines were jettisoned as planned after ~250 seconds. At an altitude of about 370 km the first stage separated from the second stage. When the second stage was ignited telemetry showed abnormal burning and the stage failed due to a malfunction in the oxidizer system. The vehicle was unable to achieve Earth orbit, re-entered and was believed to have come down somewhere in the Indian Ocean. Signals were returned by the payload for 1020 seconds after launch. The mission was designed to reach the moon approximately 62 hours after launch. Pioneer P-31
The spacecraft was launched on an Air Force-Convair Atlas D intercontinental ballistic missile coupled to Thor-Able upper stages including an Able solid propellant third stage. The vehicle exploded 68 seconds after launch at an altitude of 12 km due to a malfunction in the first stage. The payload fell into the Atlantic Ocean 12 to 20 km from Cape Canaveral in about 20 meter deep water. The Inner Pioneers Pioneers 6 through 9 were of all of the same construction, as they were all designed as tests for spacecraft operation in space. They all weighed about 68 kg (150 lbs), and were 94x88.9 cm (37x35 in.). The spacecraft were stabilized by spinning (at about once per second) and designed to last at least six months. Pioneers 6-9 demonstrated that spacecraft could be stabilized by rotation. They supplied much information about interplanetary conditions, solar activity on Earth, the solar wind, cosmic rays, the sun's plasma and magnetic fields, physics of particles in space, and the nature of sun storms which produce solar flares. By ground command, one of five bit rates, one of four data formats, and one of four operating modes could be selected. The five bit rates were 512, 256, 64, 16, and 8 bps. Three of the four data formats contained primarily scientific data and consisted of 32 seven-bit words per frame. One scientific data format was used for the two highest bit rates. Another was used for the three lowest bit rates. The third contained data from only the radio propagation experiment. The fourth data format contained mainly engineering data. The four operating modes were (1) real time, (2) telemetry store, (3) duty cycle store, and (4) memory readout. In the real-time mode, data were sampled and transmitted directly (without storage) as specified by the data format and bit rate selected. In the telemetry store mode, data were stored and transmitted simultaneously in the format and at the bit rate selected. In the duty cycle store mode, a single frame of scientific data was collected and stored at a rate of 512 bps. The time interval between the collection and storage of successive frames could be varied by ground command between 2 and 17 minutes to provide partial data coverage for periods up to 19 hours, as limited by the bit storage capacity. In the memory readout mode, data were read out at whatever bit rate was appropriate to the satellite distance from the Earth. Pioneer 6
Pioneer 6 was the first in a series of solar-orbiting, spin-stabilized, solar-cell and battery-powered satellites designed to obtain measurements on a continuing basis of interplanetary phenomena from widely separated points in space. Its experiments studied the positive ions and electrons in the solar wind, the interplanetary electron density (radio propagation experiment), solar and galactic cosmic rays, and the interplanetary magnetic field. Although the spacecraft has not been regularly tracked for science data return in recent years, a successful telemetry contact was made on December 8, 2000, to celebrate 35 years of continuous operation since launch. Pioneer 7
Pioneer 7 was the second in a series of solar-orbiting, spin-stabilized, solar-cell and battery-powered satellites designed to obtain measurements of interplanetary phenomena from widely separated points in space on a continuing basis. The spacecraft carried experiments to study positive ions and electrons in the solar wind, the interplanetary electron density (radio propagation experiment), solar and galactic cosmic rays, and the interplanetary magnetic field. The craft was last tracked successfully in March of 1995. Pioneer 8
The craft was last tracked successfully on August 22, 1996, and was commanded to its backup TWT. Pioneer 9
Pioneer 9 was the fourth in a series of solar-orbiting, spin-stabilized, and solar-cell and battery-powered satellites designed to obtain measurements of interplanetary phenomena from widely separated points in space on a continuing basis. The spacecraft carried experiments to study the positive ions and electrons in the solar wind, the interplanetary electron density (radio propagation experiment), solar and galactic cosmic rays, the interplanetary magnetic field, cosmic dust, and electric fields. Also, a new coding process was implemented for Pioneer 9. The craft circled the sun at 0.8 A.U., and it failed in 1983. Pioneer-E
Pioneer E was the fifth in a series of solar-orbiting, spin stabilized, solar-cell and battery powered satellites designed to obtain measurements of interplanetary phenomena from widely separated points on a continuing basis. Its experiments were to study the positive ions and electrons in the solar wind, the interplanetary electron density (radio propagation experiment), solar and galactic cosmic rays, the interplanetary magnetic field, cosmic dust, and electric fields. Due to a booster malfunction, the spacecraft was never put into orbit. The Outer Pioneers Pioneer 10 and 11 were designed to test the environment in the Outer Solar System, see if the asteroid belt was navigable, and to discover if the magnetic and radiation fields around Jupiter could be withstood by spacecraft. The Pioneer craft survived the asteroid belt easily. However, the ions trapped in Jupiter's magnetic field nearly fried the crafts. This was no surprise to scientists, for the radiation around Jupiter is about 1000 times the lethal dose for humans. Before their power supplies died (or nearly died), the Pioneers made valuable contributions to science. Some were proving that spacecraft could actually go this far. Others were in studying Jupiter and Saturn. Also, while they could, they studied parts of the heliopause (border of the sun's influence). They will become the first craft to head into interstellar (between stars) space (besides Voyager 1, which recently passed Pioneer 1). Pioneer 10 and 11 carry six by nine inch gold plaques which hold a graphic message on them (below). The plaques are bolted to the spacecrafts' main frame. Pioneer 10 is headed towards the constellation of Taurus (The Bull) at a speed of 12.24 km/sec (7.6 miles/sec). It will take Pioneer 10 over 2 million years to pass by Aldebran, the red star that forms the eye of the Bull. Pioneer 11 is headed toward the constellation of Aquila (The Eagle), northwest of the constellation of Sagittarius. It may pass near one of the stars in the constellation in about 4 million years. Pioneer 10
This mission was the first to be sent to the outer solar system and the first to investigate the planet Jupiter, after which it followed an escape trajectory from the solar system. The spacecraft achieved its closest approach to Jupiter on December 3, 1973, when it reached approximately 2.8 Jovian radii (about 200,000 km). As of January 1, 1997, Pioneer 10 was at about 67 A.U. from the sun near the ecliptic plane and heading outward from the sun at 2.6 A.U./year and downstream through the heliomagnetosphere towards the tail region and interstellar space. This solar system escape direction is unique because the Voyager 1 and 2 spacecraft (and Pioneer 11) are heading in the opposite direction towards the nose of the heliosphere in the upstream direction relative to the inflowing interstellar gas. The spacecraft is heading generally towards the red star Aldebran, which forms the eye of Taurus (The Bull). The journey over a distance of 68 light-years to Aldebran will require about two million years to complete. Routine tracking and project data processing operations were terminated on March 31, 1997, for budget reasons. Occasional tracking continued later under support of the Lunar Prospector project at NASA Ames Research Center with retrieval of energetic particle and radio science data. The last successful data acquisitions through NASA's Deep Space Network (DSN) occurred on March 3, 2002, the 30th anniversary of Pioneer 10's launch date, and on April 27, 2002. The spacecraft signal was last detected on January 23, 2003, after an uplink was transmitted to turn off the last operational experiment, the Geiger Tube Telescope (GTT), but lock-on to the sub-carrier signal for data downlink was not achieved. No signal at all was detected during a final attempt on February 6-7, 2003. Pioneer Project staff at NASA Ames then concluded that the spacecraft power level had fallen below that needed to power the onboard transmitter, so no further attempts would be made.
Space experiments mostly continued to operate for planetary or interplanetary measurements until failure or until insufficient spacecraft power from the RTG's was available for operation of all instruments, such that some were turned off permanently and others were cycled on and off in accordance with a power sharing plan implemented in September 1989. The Asteroid/Meteroid Detector failed in December 1973, followed by the Helium Vector Magnetometer (HVM) in November 1975 and the Infrared Radiometer in January 1974. The Meteroid Detector was turned off in October 1980 due to inactive sensors at low temperatures. The spacecraft sun sensors became inoperative in May 1986, and the Imaging Photopolarimeter (IPP) instrument was used to obtain roll phase and spin period information until being turned off in October 1993 to conserve power. The Trapped Radiation Detector (TRD) and Plasma Analyzer (PA) were respectively turned off in November 1993 and September 1995 for the same reason. As of January 1996 the final power cycling plan included part-time operations of the Charged Particle Instrument (CPI), the Cosmic Ray Telescope (CRT), the Geiger Tube Telescope (GTT), and the Ultraviolet Photometer (UV). As of August 2000, only the GTT instrument was still returning data. Various other spacecraft subsystems also either failed or were turned off for power or other reasons, and an account of these may be of interest for engineering design of long duration deep space missions. The primary antenna feed offset bellows failed sometime in 1976, but a redundant unit was available for use thereafter. The Program Storage and Execution (PSE) subsystem was turned off in September 1989 for power conservation, after which spacecraft maneuvers were performed by ground command sequences. A receiver problem in mid-1992 prevented uplink to the high gain antenna, after which uplink commands could only be sent with 70-meter DSN antennas which also supported the 16 bps downlink. The Backup Line Heater experienced a sticking thermostat operation in March 1993 for 30 days but the problem did not reoccur. Undervoltage Protection Logic was turned off in December 1993 to prevent loss of critical spacecraft systems in the event of a transient undervoltage condition. Duration and Steering Logic (DSL) was turned off in February 1995 to conserve power, after which it was turned on again only for spacecraft maneuvers. RTG power levels are low enough that the spacecraft occasionally relies in part on battery power (accumulated during inactive periods) to run experiments and other systems. The total mission cost for Pioneer 10 through the 1997 end of official science operations was about $350 million in FY 2001 U.S. dollars. This included about $200 million for pre-launch design and development, and another $150 million for launch, telemetry tracking, mission operations and data analysis. These estimates were provided by the former Pioneer Project at NASA Ames Research Center. Pioneer 11
Pioneer 11 was the second mission to investigate Jupiter and
the outer solar system and the first to explore the planet Saturn Instruments studied the interplanetary and planetary magnetic fields; solar wind properties; cosmic rays; transition region of the heliosphere; neutral hydrogen abundance; distribution, size, mass, flux, and velocity of dust particles; Jovian aurorae; Jovian radio waves; the atmospheres of planets and satellites; and the surfaces of Jupiter, Saturn, and some of their satellites. Instruments carried for these experiments were magnetometer, plasma analyzer (for solar wind), charged-particle detector, ionizing detector, non-imaging telescopes with overlapping fields of view to detect sunlight reflected from passing meteoroids, sealed pressurized cells of argon and nitrogen gas for measuring penetration of meteoroids, UV photometer, IR radiometer, and an imaging photopolarimeter, which produced photographs and measured the polarization. Further scientific information was obtained from celestial mechanics and occultation phenomena.
Pioneer 11's power supply died as of September 30, 1995, and the last communication from it was in November, 1995. Both craft cary a plaque that depicted a man and woman, the location of the sun and Earth in the galaxy, the solar system, craft, and hydrogen. The Venus Pioneers Pioneer 12
Pioneer Venus Orbiter measured the detailed structure of the upper atmosphere and ionosphere of Venus, investigated the interaction of the solar wind with the ionosphere and the magnetic field in the vicinity of Venus, determined the characteristics of the atmosphere and surface of Venus on a planetary scale, determined the planet's gravitational field harmonics from perturbations of the spacecraft orbit, and detected gamma-ray bursts. UV observations of comets have also been made. The comets and their date of observation were: Encke April 13 through April 16, 1984; Giacobini-Zinner, September 8 through 15, 1985; Halley, December 27, 1985 to March 9, 1986; Wilson, March 13 to May 2, 1987; NTT, April 8, 1987; and McNaught, November 19 through 24, 1987. The Orbiter's observation of Halley showed that when the comet comes closest to the sun, it releases 40 tons of water vapor per second. From Venus orbit insertion on December 4, 1978, to July 1980, periapsis was held between 142 and 253 km to facilitate radar and ionospheric measurements. Thereafter, the periapsis was allowed to rise (to 2290 km at maximum) and then fall, to conserve fuel. In 1991, the Radar Mapper was reactivated to investigate previously inaccessible southern portions of the planet. In May 1992, Pioneer Venus began the final phase of its mission, in which the periapsis was held between 150 and 250 km until the fuel ran out and the Orbiter ended its mission as a meteor flaming through the dense atmosphere of Venus. The orbiter cost $125 million to build and operate for the first 10 years. Pioneer 13
Pioneer 13 was commonly and collectively called the Pioneer Venus Multiprobe Mission. On August 8, 1978, slightly less than three months after Pioneer 12 left Earth, the Multiprobe spacecraft was launched from the Kennedy Space Center. Its mission was to deploy four probes into the Venusian atmosphere. On November 16, 1978, the Large Probe was released from the Bus toward an entry near the equator on the day side of Venus. Four days later, on November 20, 1978, the three Small Probes were released from the Bus. Two of the probes were targeted to enter on the night side and one was targeted to enter on the Venus day side. On December 9, 1978 the Bus with its instruments was re-targeted to enter Venus' day side. When the probes separated from the Multiprobe Bus, they went "off the air" because they did not have sufficient on-board power or solar cells to replenish their batteries. Preprogrammed instructions were wired into them and their timers had been set before they separated from the Bus. The on-board countdown timers were scheduled to bring each probe into operation again three hours before the probes began their descent through the Venusian atmosphere. On December 9, 1978, just 22 minutes before entry, the Large Probe began to transmit radio signals to Earth. Only 17 minutes before hurtling into the Venusian atmosphere at almost 42,000 km/hr (26,099 miles/hr) did all of the Small Probes started transmitting. All four probes were designed for a descent time of approximately 55 minutes before impacting the surface. None were designed to withstand the impact. However one Small Probe (the Day Probe) did survive and sent data from the surface for 67 minutes. Engineering data radioed back from the Day Probe showed that its internal temperature climbed steadily to a high of 126 °C (260 °F). Then its batteries were depleted, and its radio became silent. 
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Pioneer
1, the second and most successful of three project Able space probes and the first
spacecraft launched by the newly formed 
Pioneer
3 was a spin-stabilized spacecraft launched by the U.S. Army Ballistic Missile
agency in conjunction with NASA. The spacecraft failed to go past the moon and
into a heliocentric orbit as planned, but it did reach a maximum altitude of over
102,360 km before falling back to Earth. The revised spacecraft objectives were
to measure radiation in the outer Van Allen belt area using Geiger-Mueller tubes
and to test the trigger mechanism for a lunar photographic experiment.
Fifteen
experiments were carried to study the interplanetary and planetary magnetic fields;
solar wind parameters; cosmic rays; transition region of the heliosphere; neutral
hydrogen abundance; distribution, size, mass, flux, and velocity of dust particles;
Jovian aurorae; Jovian radio waves; atmosphere of Jupiter and some of its satellites,
particularly Io; and to photograph Jupiter and its satellites. Instruments carried
for these experiments were magnetometer, plasma analyzer, charged particle detector,
ionizing detector, non-imaging telescopes with overlapping fields of view to detect
sunlight reflected from passing meteoroids, sealed pressurized cells of argon
and nitrogen gas for measuring the penetration of meteoroids, UV photometer, IR
radiometer, and an imaging photopolarimeter, which produced photographs and measured
polarization. Further scientific information was obtained from the tracking and
occultation data.
and
its main rings. Pioneer 11, like Pioneer 10, used Jupiter's gravitational field
to alter its trajectory radically. It passed close to Saturn and then it followed
an escape trajectory from the solar system.
During
its closest approach, December 4, 1974, Pioneer 11 passed to within 34,000 km
of Jupiter's cloud tops. It passed by Saturn on September 1, 1979, at a distance
of 21,000 km from Saturn's cloud tops. The spacecraft has operated on a backup
transmitter since launch. Instrument power sharing began in February 1985 due
to declining RTG power output. Science operations and daily telemetry ceased on
September 30, 1995, when the RTG power level was insufficient to operate any experiments.
As of the end of 1995 the spacecraft was located at 44.7 A.U. from the sun at
a nearly asymptotic latitude of 17.4° above the solar equatorial plane and
was heading outward at 2.5 A.U./year.
The
Pioneer Venus Orbiter was the first of a two-spacecraft orbiter-probe combination
designed to conduct a comprehensive investigation of the atmosphere of Venus.
The spacecraft was a solar-powered cylinder about 250 cm in diameter with its
spin axis spin-stabilized perpendicular to the ecliptic plane. A high-gain antenna
was mechanically de-spun to remain focused on the earth. The instruments were
mounted on a shelf within the spacecraft except for a magnetometer mounted at
the end of a boom to ensure against magnetic interference from the spacecraft.