- Pioneer 11 Jupiter encounter
- Approach on Jupiter
- The Great Red Spot imaged by Pioneer 11
- The Great Red Spot prior to closest approach
An artist's impression of a Pioneer spacecraft on its way to interstellar space.
|Mission type||Planetary and heliosphere exploration|
|Operator||NASA / ARC|
|Website|| Pioneer Project website (archived)|
NASA Archive page
|Mission duration||22 years, 5 months, 25 days|
|Launch mass||259 kilograms (571 lb)|
|Power||155 watts (at launch)|
|Start of mission|
|Launch date||April 6, 1973, 02:11:00 UTC|
|Rocket||Atlas SLV-3D Centaur-D1A Star-37E|
|Launch site||Cape Canaveral LC-36B|
|End of mission|
|Last contact||September 30, 1995|
|Flyby of Jupiter|
|Closest approach||December 3, 1974|
|Distance||43,000 kilometers (27,000 miles)|
|Flyby of Saturn|
|Closest approach||September 1, 1979|
|Distance||21,000 kilometers (13,000 miles)|
Pioneer 11 (also known as Pioneer G) is a 259-kilogram (571 lb) robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind and cosmic rays. It was the first probe to encounter Saturn and the second to fly through the asteroid belt and by Jupiter. Thereafter, Pioneer 11 became the second of five artificial objects to achieve the escape velocity that will allow them to leave the Solar System. Due to power constraints and the vast distance to the probe, the last routine contact with the spacecraft was on September 30, 1995, and the last good engineering data was received on November 24, 1995.
A robotic spacecraft is an uncrewed spacecraft, 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 lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spacecraft technology, so telerobotic probes are the only way to explore them.
A space probe is a robotic spacecraft that does not orbit Earth, but instead, explores further into outer space. A space probe may approach the Moon; travel through interplanetary space; flyby, orbit, or land on other planetary bodies; or enter interstellar space.
The National Aeronautics and Space Administration is an independent agency of the United States Federal Government responsible for the civilian space program, as well as aeronautics and aerospace research.
Approved in February 1969, Pioneer 11 and its twin probe, Pioneer 10 , were the first to be designed for exploring the outer Solar System. Yielding to multiple proposals throughout the 1960s, early mission objectives were defined as:
Pioneer 10 is an American space probe, launched in 1972 and weighing 258 kilograms, that completed the first mission to the planet Jupiter. Thereafter, Pioneer 10 became the first of five artificial objects to achieve the escape velocity that will allow them 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.
The interplanetary medium (IPM) is the material which fills the Solar System, and through which all the larger Solar System bodies, such as planets, dwarf planets, asteroids, and comets, move.
The atmosphere of Jupiter is the largest planetary atmosphere in the Solar System. It is mostly made of molecular hydrogen and helium in roughly solar proportions; other chemical compounds are present only in small amounts and include methane, ammonia, hydrogen sulfide and water. Although water is thought to reside deep in the atmosphere, its directly measured concentration is very low. The nitrogen, sulfur, and noble gas abundances in Jupiter's atmosphere exceed solar values by a factor of about three.
Subsequent planning for an encounter with Saturn added many more goals:
The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma consists of mostly electrons, protons and alpha particles with kinetic energy between 0.5 and 10 keV. Embedded within the solar-wind plasma is the interplanetary magnetic field. The solar wind varies in density, temperature and speed over time and over solar latitude and longitude. Its particles can escape the Sun's gravity because of their high energy resulting from the high temperature of the corona, which in turn is a result of the coronal magnetic field.
Radio occultation (RO) is a remote sensing technique used for measuring the physical properties of a planetary atmosphere or ring system.
Pioneer 11 was built by TRW and managed as part of the Pioneer program by NASA Ames Research Center. 266–8A backup unit, Pioneer H, is currently on display in the "Milestones of Flight" exhibit at the National Air and Space Museum in Washington, D.C.. Many elements of the mission proved to be critical in the planning of the Voyager program. :
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, including Pioneer 1, Pioneer 10, and several space-based observatories. It was #57 on the 1986 Fortune 500 list, and had 122,258 employees. In 1958 the company was called Thompson Ramo Wooldridge, after three prominent leaders. This was later shortened to TRW.
The Pioneer program was a series of United States unmanned space missions that were 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. Pioneer 10 and Pioneer 11 carry a golden plaque, depicting a man and a woman and information about the origin and the creators of the probes, should any extraterrestrials find them someday.
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 Pioneer 11 bus measured 36 centimeters (14 in) deep and with six 76-centimeter-long (30 in) panels forming the hexagonal structure. The bus housed propellant to control the orientation of the probe and eight of the twelve scientific instruments. The spacecraft had a mass of 260 kilograms. :42
Pioneer had one additional instrument more than Pioneer 10, a flux-gate magnetometer.
|Helium Vector Magnetometer (HVM)|
|Measured the fine structure of the interplanetary magnetic field, mapped the Jovian magnetic field, and provided magnetic field measurements to evaluate solar wind interaction with Jupiter.|
|Quadrispherical Plasma Analyzer|
|Peered through a hole in the large dish-shaped antenna to detect particles of the solar wind originating from the Sun.|
|Charged Particle Instrument (CPI)|
|Detected cosmic rays in the Solar System.|
|Cosmic Ray Telescope (CRT)|
|Collected data on the composition of the cosmic ray particles and their energy ranges.|
|Geiger Tube Telescope (GTT)|
|Surveyed the intensities, energy spectra, and angular distributions of electrons and protons along the spacecraft's path through the radiation belts of Jupiter and Saturn.|
|Trapped Radiation Detector (TRD)|
Included an unfocused Cerenkov counter that detected the light emitted in a particular direction as particles passed 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 measured minimum ionizing particles (<3 MeV) and protons in the range of 50 to 350 MeV.
|Twelve panels of pressurized cell detectors mounted on the back of the main dish antenna recorded penetrating impacts of small meteoroids. |
|Asteroid/Meteoroid Detector (AMD)|
|Meteoroid-asteroid detector looked into space with four non-imaging telescopes to track particles ranging from close-by bits of dust to distant large asteroids. |
|Ultraviolet light was sensed to determine the quantities of hydrogen and helium in space and on Jupiter and Saturn.|
|Imaging Photopolarimeter (IPP)|
|The imaging experiment relied 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.|
|Provided information on cloud temperature and the output of heat from Jupiter and Saturn.|
|Triaxial Fluxgate Magnetometer|
|Measured the magnetic fields of both Jupiter and Saturn. This instrument was not carried on Pioneer 10. |
|Timeline of travel|
The Pioneer 11 probe was launched on April 6, 1973 at 02:11:00 UTC, by the National Aeronautics and Space Administration from Space Launch Complex 36A at Cape Canaveral, Florida aboard an Atlas-Centaur launch vehicle. Its twin probe, Pioneer 10 , had launched a year earlier on March 3, 1972. Pioneer 11 was launched on a trajectory directly aimed at Jupiter without any prior gravitational assists. km/h. It also made two mid-course corrections, on April 11, 1973 and November 7, 1974.In May 1974, Pioneer was retargeted to fly past Jupiter on a north-south trajectory enabling a Saturn flyby in 1979. The maneuver used 17 pounds of propellant, lasted 42 minutes and 36 seconds and increased Pioneer 11's speed by 230
Pioneer 11 flew past Jupiter in November and December 1974. During its closest approach, on December 2, it passed 42,828 kilometers (26,612 mi) above the cloud tops. The probe obtained detailed images of the Great Red Spot, transmitted the first images of the immense polar regions, and determined the mass of Jupiter's moon Callisto. Using the gravitational pull of Jupiter, a gravity assist was used to alter the trajectory of the probe towards Saturn. On April 16, 1975, following the Jupiter encounter, the micrometer detector was turned off.
Pioneer 11 passed by Saturn on September 1, 1979, at a distance of 21,000 km from Saturn's cloud tops.
By this time Voyager 1 and Voyager 2 had already passed Jupiter and were also en route to Saturn, so it was decided to target Pioneer 11 to pass through the Saturn ring plane at the same position that the soon-to-come Voyager probes would use in order to test the route before the Voyagers arrived. If there were faint ring particles that could damage a probe in that area, mission planners felt it was better to learn about it via Pioneer. Thus, Pioneer 11 was acting as a "pioneer" in a true sense of the word; if danger were detected, then the Voyager probes could be rerouted further away from the rings, but missing the opportunity to visit Uranus and Neptune in the process.
Pioneer 11 imaged and nearly collided with one of Saturn's small moons, passing at a distance of no more than 4,000 kilometers (2,500 mi). The object was tentatively identified as Epimetheus, a moon discovered the previous day from Pioneer's imaging, and suspected from earlier observations by Earth-based telescopes. After the Voyager flybys, it became known that there are two similarly-sized moons (Epimetheus and Janus) in the same orbit, so there is some uncertainty about which one was the object of Pioneer's near-miss. Pioneer 11 encountered Janus on September 1, 1979 at 14:52 UTC at a distance of 2500 km and Mimas at 16:20 UTC the same day at 103000 km.
Besides Epimetheus, instruments located another previously undiscovered small moon 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, the probe sent back 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.
On February 25, 1990, Pioneer 11 became the 4th man-made object to pass beyond the orbit of the planets.
By 1995, Pioneer 11 could no longer power any of its detectors, so the decision was made to shut it down.On September 29, 1995, NASA's Ames Research Center, responsible for managing the project, issued a press release that began, "After nearly 22 years of exploration out to the farthest reaches of the Solar System, one of the most durable and productive space missions in history will come to a close." It indicated NASA would use its Deep Space Network antennas to listen "once or twice a month" for the spacecraft's signal, until "some time in late 1996" when "its transmitter will fall silent altogether." NASA Administrator Daniel Goldin characterized Pioneer 11 as "the little spacecraft that could, a venerable explorer that has taught us a great deal about the Solar System and, in the end, about our own innate drive to learn. Pioneer 11 is what NASA is all about – exploration beyond the frontier." Besides announcing the end of operations, the dispatch provided a historical list of Pioneer 11 mission achievements. NASA terminated routine contact with the spacecraft on September 30, 1995, but continued to make contact for about 2 hours every 2 to 4 weeks. Scientists received a few minutes of good engineering data on 24 November 1995 but then lost final contact once Earth permanently moved out of view of the spacecraft's antenna. Its signal became too faint to hear in 2002.
On January 30, 2019, Pioneer 11 was 100.84 AU (1.5085×1010 km; 9.374×109 mi) from the Earth and 100 AU (1.5×1010 km; 9.3×109 mi) from the Sun; and traveling at 11.241 km/s (40,470 km/h; 25,150 mph) (relative to the Sun) and traveling outward at about 2.37 AU per year. The spacecraft is heading in the direction of the constellation Scutum near the current position (August 2017) RA 18h 50m dec -8° 39.5' (J2000.0) close to Messier 26. In 928,000 years it will pass within 0.25pc of the K dwarf TYC 992-192-1.
Pioneer 11 has now been overtaken by the two Voyager probes, launched in 1977, and Voyager 1 is now the most distant object built by humans.
Analysis of the radio tracking data from the Pioneer 10 and 11 spacecraft at distances between 20–70 AU from the Sun has consistently indicated the presence of a small but anomalous Doppler frequency drift. The drift can be interpreted as due to a constant acceleration of (8.74 ± 1.33) × 10−10 m/s2 directed towards the Sun. Although it is suspected that there is a systematic origin to the effect, none was found. As a result, there is sustained interest in the nature of this so-called "Pioneer anomaly". Extended analysis of mission data by Slava Turyshev and colleagues has determined the source of the anomaly to be asymmetric thermal radiation and the resulting thermal recoil force acting on the face of the Pioneers away from the Sun, and in July 2012 the group of researchers published their results in the Physical Review Letters scientific journal.
Pioneer 10 and 11 both carry a gold-anodized aluminum plaque in the event that either spacecraft is ever found by intelligent lifeforms from other planetary systems. 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.
In 1991, Pioneer 11 was honored on one of 10 United States Postage Service stamps commemorating unmanned spacecraft exploring each of the then nine planets and the Moon. Pioneer 11 was the spacecraft featured with Jupiter. Pluto was listed as "Not yet explored".
Galileo was an American unmanned spacecraft that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989 by Space ShuttleAtlantis. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit Jupiter. It launched the first probe into Jupiter, directly measuring its atmosphere. Despite suffering major antenna problems, Galileo achieved the first asteroid flyby, of 951 Gaspra, and discovered the first asteroid moon, Dactyl, around 243 Ida. In 1994, Galileo observed Comet Shoemaker–Levy 9's collision with Jupiter.
Voyager 1 is a space probe launched by NASA on September 5, 1977. Part of the Voyager program to study the outer Solar System, Voyager 1 was launched 16 days after its twin, Voyager 2. Having operated for 41 years, 7 months and 6 days as of April 11, 2019, the spacecraft still communicates with the Deep Space Network to receive routine commands and to transmit data to Earth. At a distance of 145 AU from Earth as of February 22, 2019, it is the most distant from Earth of all known human-made objects.
Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets.
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth. It has only one-eighth the average density of Earth, but with its larger volume Saturn is over 95 times more massive. Saturn is named after the Roman god of agriculture; its astronomical symbol (♄) represents the god's sickle.
The Voyager program is an American scientific program that employs two robotic probes, Voyager 1 and Voyager 2, to study the outer Solar System. The probes were launched in 1977 to take advantage of a favorable alignment of Jupiter, Saturn, Uranus and Neptune. Although their original mission was to study only the planetary systems of Jupiter and Saturn, Voyager 2 continued on to Uranus and Neptune. The Voyagers now explore the outer boundary of the heliosphere in interstellar space; their mission has been extended three times and they continue to transmit useful scientific data. Neither Uranus nor Neptune has been visited by a probe other than Voyager 2.
The Cassini–Huygens mission, commonly called Cassini, was a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a probe to study the planet Saturn and its system, including its rings and natural satellites. The Flagship-class robotic spacecraft comprised both NASA's Cassini probe, and ESA's Huygens lander which landed on Saturn's largest moon, Titan. Cassini was the fourth space probe to visit Saturn and the first to enter its orbit. The craft were named after astronomers Giovanni Cassini and Christiaan Huygens.
In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft, typically to save propellant and reduce expense.
The outer planets are those planets in the Solar System beyond the asteroid belt, and hence refers to the gas giants and ice giants, which are in order of their distance from the Sun:
The exploration of Jupiter has been conducted via close observations by automated spacecraft. It began with the arrival of Pioneer 10 into the Jovian system in 1973, and, as of 2016, has continued with eight further spacecraft missions. All of these missions were undertaken by the National Aeronautics and Space Administration (NASA), and all but two have been flybys that take detailed observations without the probe landing or entering orbit. These probes make Jupiter the most visited of the Solar System's outer planets as all missions to the outer Solar System have used Jupiter flybys to reduce fuel requirements and travel time. On 5 July 2016, spacecraft Juno arrived and entered the planet's orbit—the second craft ever to do so. Sending a craft to Jupiter entails many technical difficulties, especially due to the probes' large fuel requirements and the effects of the planet's harsh radiation environment.
The exploration of Uranus has, to date, been solely through telescopes and NASA's Voyager 2 spacecraft, which made its closest approach to Uranus on January 24, 1986. Voyager 2 discovered 10 moons, studied the planet's cold atmosphere, and examined its ring system, discovering two new rings. It also imaged Uranus' five large moons, revealing that their surfaces are covered with impact craters and canyons.
The exploration of Saturn has been solely performed by crewless probes. Three missions were flybys, which formed an extended foundation of knowledge about the system. The Cassini–Huygens spacecraft, launched in 1997, was in orbit from 2004 to 2017.
Discovery and exploration of the Solar System is observation, visitation, and increase in knowledge and understanding of Earth's "cosmic neighborhood". This includes the Sun, Earth and the Moon, the major planets including Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune, their satellites, as well as smaller bodies including comets, asteroids, and dust.
The Solar System — our Sun’s system of planets, moons, and smaller debris — is humankind’s cosmic backyard. Small by factors of millions compared to interstellar distances, the spaces between the planets are daunting, but technologically surmountable
JunoCam is the visible-light camera/telescope of the Juno Jupiter orbiter, a NASA space probe launched to the planet Jupiter on 5 August 2011. It was built by Malin Space Science Systems. The telescope/camera has a field of view of 58 degrees with four filters. The camera is run by the JunoCam Digital Electronics Assembly (JDEA) also made by MSSS. It takes a swath of imaging as the spacecraft rotates; the camera is fixed to the spacecraft so as it rotates, it gets one sweep of observation.
The discrepancy caused by the anomaly amounts to about 248,500 miles (399,900 kilometres), or roughly the distance between Earth and the Moon. That's how much farther the probes should have traveled in their 34 years, if our understanding of gravity is correct.
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