space probes

Nakayla Blount

What is space probe?



  • space probes are in space floating around and tell the the people what is going on in space.


  • Sputnik 1 was the first probe to go into space. It was launched on Oct. 4, 1957, by the former Soviet Union. On Jan. 31, 1958, the United States sent a probe called Explorer 1 into space. These first probes studied Earth from space. They also learned what it's like to be in space. This was the beginning of the Space Race between the United States and Soviet Union.

    Once probes could reach space, the two countries started sending probes to fly past the moon and other planets. Mariner 2 was the first probe to study another planet. On Dec. 14, 1962, Mariner 2 flew past the planet Venus. It confirmed that Venus is very hot.

    A different probe, called Mariner 4, was the first probe to snap a picture of a planet. On July 14, 1965, Mariner 4 flew past Mars. Its images of Mars showed a cold, cratered, moon-like surface.

    • closest encounter (flybys)
    • impact (impactors)
    • orbital insertion to end of mission, whether planned or premature (orbiters)
    • landing to end of mission, whether planned or premature (landers)
    • launch (missions that never got underway due to failure at or soon after launch)
    In cases which do not fit any of the above, the event to which the date refers is stated. Note that as a result of this scheme missions are not always listed in order of launch.
    • Some of the terms used under Type:
    • Flyby: The probe flies by an astronomical body, but does not orbit it
    • Orbiter: Part of a probe that orbits an astronomical body
    • Lander: Part of a probe that descend to the surface of an astronomical body
    • Rover: Part of a probe that acts as a vehicle to move on the solid-surface of an astronomical body
    • Penetrator: Part of a probe that impacts an astronomical body
    • Atmospheric probe or balloon: Part of a probe that descend through or floats in the atmosphere of an astronomical body
    • Sample return: Parts of the probe return back to Earth with physical samples
    • Under Status, in the case of flybys (such as gravity assists) that are incidental to the main mission, "success" indicates the successful completion of the flyby, not necessarily that of the main mission.

    In 1971, Mariner 9 arrived at Mars and became the first probe to orbit, or circle, another planet. Mariner 9 took a picture of Mars that showed the largest volcano in the solar system.

    Probes Over Time

    Many probes study Earth or measure properties of space. Other probes use telescopes or other instruments to study planets, stars, and galaxies that are far away. Probes that travel to other planets have changed from simple machines that could study a few features of a planet to sophisticated probes that travel great distances to study a wide range of features on planets, moons, asteroids and comets. We tend to call these more sophisticated probes spacecraft, orbiters, landers and rovers.

    One of the most famous probes is Voyager 1. It has traveled further in space than any human-made object. It launched into space in 1977. Voyager 1 flew past Jupiter and Saturn and then headed for the edge of our solar system. As of Feb. 1, 2010, the spacecraft was 16.8 billion kilometers (about 10.4 billion miles) from Earth.

    For more information about JPL probes and missions go to http://www.jpl.nasa.gov/missions/index.cfm .

    For a timeline of robotic exploration, go to http://sse.jpl.nasa.gov/history/index.cfm .

    More research topics:

    Explorer 1
    Sputnik 1
    Voyager Mission
    Mariner 9

    Have a Quest

    Mariner 2the first successful probe to flyby Venus in December of 1962, and it returned information which confirmed that Venus is a very hot (800 degrees Fahrenheit, now revised to 900 degrees F.) world with a cloud-covered atmosphere composed primarily of carbon dioxide.

    (more info from NASA Spacelink)


    Mariner 3launched on November 5, 1964, was lost when its protective shroud failed to eject as the craft was placed into interplanetary space. Unable to collect the Sun's energy for power from its solar panels, the probe soon died when its batteries ran out and is now in solar orbit. It was intended for a Marsflyby with Mariner 4.


    Mariner 4the sister probe to Mariner 3, did reach Mars in 1965 and took the first close-up images of the Martian surface (22 in all) as it flew by the planet. The probe found a cratered world with an atmosphere much thinner than previously thought. Many scientists concluded from this preliminary scan that Mars was a "dead" world in both the geological and biological sense.


    Mariner 9Mariner 9, the sister probe to Mariner 8 which failed on launch, became the first craft to orbit Mars in 1971. It returned information on the Red Planet that no other probe had done before, revealing huge volcanoes on the Martian surface, as well as giant canyon systems, and evidence that water once flowed across the planet. The probe also took the first detailed closeup images of Mars' two small moons, Phobos and Deimos.


    Apollo6 manned landings on the Moon and sample returns 1969-72. (The seventh landing, Apollo 18, was canceled for political reasons)

    (Apollo "home page"; Apollo Missions)


    Luna 16automated sample return from the Moon 1970 (USSR)


    Pioneer 10 and Pioneer 11Pioneer 10 was the first spacecraft to flyby Jupiter in 1973. Pioneer 11 followed it in 1974, and then went on to become the first probe to study Saturn in 1979. The Pioneers were designed to test the ability of spacecraft to survive passage thru the asteroid belt and Jupiter's magnetosphere. The asteroid belt was easy, but they were nearly fried by ions trapped in Jupiter's magnetic field. This information was crucial to the success of the Voyager missions.

    Pioneer 11's RTG power supply is dead. Its last communication with Earth was in November 1995. Pioneer 10 is still functioning (barely) but is no longer being tracked regularly due to budget cutbacks. The last data was received from it on 1997 March 31. They are heading off into interstellar space, the first craft ever to do so.

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

    (Pioneer Project Home Page and more about Pioneer 10 and Pioneer 11 from NASA Spacelink )


    Mariner 10used Venus as a gravity assist to Mercury in 1974. The probe did return the first close-up images of the Venusian atmosphere in ultraviolet, revealing previously unseen details in the cloud cover, plus the fact that the entire cloud system circles the planet in four Earth days. Mariner 10 eventually made three flybys of Mercury from 1974 to 1975 before running out of attitude control gas. The probe revealed Mercury as a heavily cratered world with a mass much greater than thought. This would seem to indicate that Mercury has an iron core which makes up 75 percent of the entire planet.

    (more from JPL and JPL)


    Venera 7First probe to return data from the surface of another planet (Venus) in 1970.


    Venera 9soft landing on Venus, pictures of the surface 1975. (USSR) This was the first spacecraft to land on the surface of another planet.


    Pioneer Venus1978; orbiter and four atmospheric probes; made the first high-quality map of the surface of Venus.

    (more info from NASA Spacelink; and NSSDC a tutorial from UCLA)


    Viking 1Viking 1 was launched from Cape Canaveral, Florida on August 20, 1975 on a TITAN 3E-CENTAUR D1 rocket. The probe went into Martian orbit on June 19, 1976, and the lander set down on the western slopes of Chryse Planitia on July 20, 1976. It soon began its programmed search for Martian micro-organisms (there is still debate as to whether the probes found life there or not), and sent back incredible color panoramas of its surroundings. One thing scientists learned was that Mars' sky was pinkish in color, not dark blue as they originally thought (the sky is pink due to sunlight reflecting off the reddish dust particles in the thin atmosphere). The lander set down among a field of red sand and boulders stretching out as far as its cameras could image.


    Viking 2Viking 2 was launched on September 9, 1975, and arrived in Martian orbit on August 7, 1976. The lander touched down on September 3, 1976 in Utopia Planitia. It accomplished essentially the same tasks as its sister lander, with the exception that its seismometer worked, recording one marsquake.

    The last data from Viking (Lander 1) made its final transmission to Earth Nov. 11, 1982. Controllers at JPL tried unsuccessfully for another six and one-half months to regain contact with Viking Lander 1. The overall mission came to an end May 21, 1983.

    An interesting side note: Viking 1's lander has been designated the Thomas A. Mutch Memorial Station in honor of the late leader of the lander imaging team. The National Air and Space Museum in Washington, DC is entrusted with the safekeeping of the Mutch Station Plaque until it can be attached to the lander by a manned expedition.

    (more info (pdf) and an web page from JPL)


    Voyager 1Voyager 1 (image at top) was launched September 5, 1977, and flew past Jupiter on March 5, 1979 and by Saturn on November 13, 1980. Voyager 2 was launched August 20, 1977 (before Voyager 1), and flew by Jupiter on August 7, 1979, by Saturn on August 26, 1981, by Uranus on January 24, 1986, and by Neptune on August 8, 1989. Voyager 2 took advantage of a rare once-every-189-years alignment to slingshot its way from outer planet to outer planet. Voyager 1 could, in principle, have headed towards Pluto, but JPL opted for the sure thing of a Titan close up.

    Between the two probes, our knowledge of the 4 giant planets, their satellites, and their rings has become immense. Voyager 1 & 2 discovered that Jupiter has complicated atmospheric dynamics, lightning and aurorae. Three new satellites were discovered. Two of the major surprises were that Jupiter has rings and that Io has active sulfurous volcanoes, with major effects on the Jovian magnetosphere.

    When the two probes reached Saturn, they discovered over 1000 ringlets and 7 satellites, including the predicted shepherd satellites that keep the rings stable. The weather was tame compared with Jupiter: massive jet streams with minimal variance (a 33-year great white spot/band cycle is known).Titan's atmosphere was smoggy. Mimas's appearance was startling: one massive impact crater gave it the Death Star appearance. The big surprise here was the stranger aspects of the rings. Braids, kinks, and spokes were both unexpected and difficult to explain.

    Voyager 2Voyager 2, thanks to heroic engineering and programming efforts, continued the mission to Uranusand Neptune. Uranus itself was highly monochromatic in appearance. One oddity was that its magnetic axis was found to be highly skewed from the already completely skewed rotational axis, giving Uranus a peculiar magnetosphere. Icy channels were found on Ariel, and Miranda was a bizarre patchwork of different terrains. 10 satellites and one more ring were discovered.

    In contrast to Uranus, Neptune was found to have rather active weather, including numerous cloud features. The ring arcs turned out to be bright patches on one ring. Two other rings, and 6 other satellites, were discovered. Neptune's magnetic axis was also skewed. Triton had a canteloupe appearance and geysers. (What's liquid at 38K?)

    If no unforeseen failures occur, we will be able to maintain communications with both spacecraft until at least the year 2030. Both Voyagers have plenty of hydrazine fuel -- Voyager 1 is expected to have enough propellant until 2040 and Voyager 2 until 2034. The limiting factor is the RTGs (radio-isotope thermal generators). The power output from the RTGs is slowly dropping each year. By 2000, there won't be enough power for the UVS (ultraviolet spectrometer) instrument. By 2010, the power will have dropped low enough such that not all of the fields and particles instruments can be powered on at the same time. A power sharing plan will go into effect then, where some of the F & P instruments are powered on, and others off. The spacecraft can last in this mode for about another 10 years, and after that the power will probably be too low to maintain the spacecraft.

    (the Voyager Project Home Page from JPL; another nice "home page" at NSSDC; fact sheets and a web page from JPL )


    VegaInternational project VENUS-HALLEY, launched in 1984, carried a Venus orbiter and lander and did a fly-by of Comet Halley.

    (Vega Mission Home page


    PhobosTwo spacecraft were launched by the USSR in 1988. One failed without a trace. A few images were returned before the second one failed, too.

    (Phobos Mission Home page


    GiottoGiotto was launched by an Ariane-1 by ESA on July 2 1985, and approached within 540 km +/- 40 km of the nucleus of Comet Halley on March 13, 1986. The spacecraft carried 10 instruments including a multicolor camera, and returned data until shortly before closest approach, when the downlink was temporarily lost. Giotto was severely damaged by high-speed dust encounters during the flyby and was placed into hibernation shortly afterwards.

    In April, 1990, Giotto was reactivated. 3 of the instruments proved fully operational, 4 partially damaged but usable, and the remainder, including the camera, were unusable. On July 2, 1990, Giotto made a close encounter with Earth and was retargeted to a successful flyby of comet Grigg-Skjellerup on July 10, 1992.

    (more info from NSSDC)


    Clementinea joint mission of the Ballistic Missile Defense Organization (formerly SDIO) and NASA to flight test sensors developed by Lawrence Livermore for BMDO. The spacecraft, built by the Naval Research Lab, was launched on January 25 1994 to a 425 km by 2950 km orbit of the Moon for a 2 month mapping mission. Instruments onboard include UV to mid-IR imagers, including an imaging lidar that may be able to also obtain altimetric data for the middle latitudes of the Moon. In early May the spacecraft was to have been sent out of lunar orbit toward a flyby of the asteroid 1620 Geographos but a failure prevented the attempt.

    Ground controllers have regained control of the spacecraft, however. Its potential future mission is being considered.

    (for more information see the Clementine Mission Home page from USGS and the Clementine page from NASA PDS or The Clementine Mission from LPI.)


    Mars ObserverMars orbiter including 1.5 m/pixel resolution camera. Launched 9/25/92 on a Titan III/TOS booster. Contact was lost with MO on 8/21/93 while it was preparing for entry into Mars orbit. The spacecraft has been written off (postmortem analysis). Mars Global Surveyor, a replacement mission to achieve most of MO's science goals, has been very successful.


    MagellanLaunched in May 1989, Magellan has mapped 98% of the surface of Venus at better than 300 meter resolution and obtained a comprehensive gravity field map for 95 percent of the planet. Magellan recently executed an 80-day aerobraking program to lower and circularize its orbit. Magellan has completed its radar mapping and gravity data collection. In the fall of 1994, just before it would have failed due to deterioration in its solar panels, Magellan was deliberately sent into Venus' atmosphere to further study aerobraking techniques which can make major savings in fuel for future missions.

    (more info (pdf), a web page and another web page from JPL; fact sheet from NSSDC)


    GalileoJupiter orbiter and atmosphere probe. It made extensive surveys of the Jovian moons and the probe descended into Jupiter's atmosphere to provide our first direct evidence of the interior of a gas giant.

    In addition, Galileo has returned the first resolved images of two asteroids, 951 Gaspraand 243 Ida, while in transit to Jupiter. It also returned pictures of the impact of Comet SL9 onto Jupiter from its unique vantage point.

    Galileo was deliberately crashed in to Jupiter in 2003 to prevent any possibility that it might crash into Europa and contaminate any life that might be there.

    (Education and Public Outreach (images!); Galileo Home Page; Galileo Probe Home Page from ARC;web page; NSSDC page; preliminary Galileo Probe Results from JPL and LANL)


    Mars 96a large orbiter with several landers originally known as Mars 94. Launch failed 1996 November 17. (The original Mars 96 was known for a while as Mars 98 and then cancelled.) (more info from MSSS andfrom IKI (Russia))


    PathfinderThe Mars Pathfinder (formerly known as the Mars Environmental Survey, or MESUR, Pathfinder) is the second of NASA's low-cost planetary Discovery missions. The mission consists of a stationary lander and a surface rover known as Sojourner. The mission has the primary objective of demonstrating the feasibility of low-cost landings on and exploration of the Martian surface. This objective will be met by tests of communications between the rover and lander, and the lander and Earth, and tests of the imaging devices and sensors.

    The scientific objectives include atmospheric entry science, long-range and close-up surface imaging, with the general objective being to characterize the Martian environment for further exploration. The spacecraft will enter the Martian atmosphere without going into orbit around the planet and land on Mars with the aid of parachutes, rockets and airbags, taking atmospheric measurements on the way down. Prior to landing, the spacecraft will be enclosed by three triangular solar panels (petals), which will unfold onto the ground after touchdown.

    Mars Pathfinder was launched 1996 December 4 and landed successfully on Mars on 1997 July 4.

    ( MPF Home Page from JPL; more info from NSSDC; images and press releases from MSFC; Mars Watch, Linking Amateur and Professional Mars Observing Communities for Observational Support of the Mars Pathfinder Mission)


    NEARThe Near Earth Asteroid Rendezvous (NEAR) mission promises to answer fundamental questions about the nature of near-Earth objects such as asteroids and comets.

    Launched on 1996 February 17 aboard a Delta 2 rocket, the NEAR spacecraft should arrive in orbit around asteroid 433 Eros in early January 1999. It will then survey the rocky body for a minimum of one year, at altitudes as close as 15 miles (24 kilometers). Eros is one of the largest and best-observed asteroids whose orbits cross Earth's path. These asteroids are closely related to the more numerous "Main Belt" asteroids that orbit the Sun in a vast doughnut-shaped ring between Mars and Jupiter.

    (NEAR Home Page; more info from NSSDC; more from John Hopkins Univ.; Curriculum materials)


    Lunar ProspectorLunar Prospector, the first NASA mission to the Moon in almost 30 years, was launched Jan 6th, 1998. Within a month it will begin returning answers to long-standing questions about the Moon, its resources, its structure and its origins. (Welcome to the Moon, Lunar Prospector home page); morefrom NSSDC

    Ongoing Missions

    Voyager 1 and 2still operational after more than 15 years in space and are traveling out of the Solar System. The two Voyagers are expected to last until at least the year 2015 when their radioisotope thermoelectric generators (RTG) power supplies are expected for fail. Their trajectories give negative evidence about possible planets beyond Pluto. Their next major scientific discovery should be the location of theheliopause. Low-frequency radio emissions believed to originate at the heliopause have been detected by both Voyagers.

    Both Voyagers are using their ultraviolet spectrometers to map the heliosphere and study the incoming interstellar wind. The cosmic ray detectors are seeing the energy spectra of interstellar cosmic rays in the outer heliosphere

    Voyager 1 has passed the Pioneer 10 spacecraft and is now the most distant human-made object in space.

    (more info from JPL)


    Hubble Space Telescopelaunched April 1990; fixed December 1993. HST can provide pictures and spectra over a long period of time. This provides an important extra dimension to the higher resolution data from the planetary probes. For example, recent HST data show that Mars is colder and drier than during the Viking missions; and HST images of Neptune indicate that its atmospheric features change rapidly.

    Named for the American astronomer Edwin Hubble.

    Much, much more information about HST and HST pictures are available at the Space Telescope Science Institute. HST's latest images are posted regularly. (Here is a brief history of the HST project. There's also some more HST info at JPL.)


    Ulyssesnow investigating the Sun's polar regions (European Space Agency/NASA). Ulysses was launched by the Space Shuttle Discovery in October 1990. In February 1992, it got a gravity boost from Jupiter to take it out of the plane of the ecliptic. It has now completed its main mission of surveying both of the Sun's poles. Its mission has been extended for another orbit so that it can survey the Sun's poles near the maximum of the sunspot cycle, too. Its aphelion is 5.2 AU, and, surprisingly, its perihelion is about 1.5 AU-- that's right, a solar-studies spacecraft that's always further from the Sun than the Earth is! It is expected to provide a much better understanding of the Sun's magnetic field and the solar wind.

    (Ulysses Home Pages from JPL and ESA)


    WindAfter its November 1, 1994, launch, NASA's Wind satellite will take up a vantage point between the Sun and the Earth, giving scientists a unique opportunity to study the enormous flow of energy and momentum known as the solar wind.

    The main scientific goal of the mission is to measure the mass, momentum and energy of the solar wind that somehow is transferred into the space environment around the Earth. Although much has been learned from previous space missions about the general nature of this huge transfer, it is necessary to gather a great deal of detailed information from several strategic regions of space around the Earth before scientists understand the ways in which the planet's atmosphere responds to changes in the solar wind.

    The launch also marks the first time a Russian instrument will fly on an American spacecraft. The Konus Gamma-Ray Spectrometer instrument, provided by the Ioffe Institute, Russia, is one of two instruments on Wind which will study cosmic gamma-ray bursts, rather than the solar wind. A French instruments is also aboard.

    At first, the satellite will have a figure-eight orbit around the Earth with the assistance of the Moon's gravitational field. Its furthest point from the Earth will be up to 990,000 miles (1,600,000 kilometers), and its closest point will be at least 18,000 miles (29,000 kilometers).

    Later in the mission, the Wind spacecraft will be inserted into a special halo orbit in the solar wind upstream from the Earth, at the unique distance which allows Wind to always remain between the Earth and the Sun (about 930,000 to 1,050,000 miles, or 1,500,000 to 1,690,000 kilometers, from the Earth).


    Mars Surveyor ProgramLaunched with a Delta II expendable vehicle from Cape Canaveral, Fla., on November 7 1996, the spacecraft is now in orbit around Mars. The spacecraft circles Mars once every two hours, maintaining a "sun synchronous" orbit that will put the sun at a standard angle above the horizon in each image and allow the mid-afternoon lighting to cast shadows in such a way that surface features will stand out. The spacecraft will carry a portion of the Mars Observer instrument payload and will use these instruments to acquire data of Mars for a full Martian year, the equivalent of about two Earth years. The spacecraft will then be used as a data relay station for signals from U.S. and international landers and low-altitude probes for an additional three years.

    (MGS Home Page from JPL; Planned Missions from 1996 to 2003)

    CassiniSaturn orbiter and Titan atmosphere probe. Cassini is a joint NASA/ESA project designed to accomplish an exploration of the Saturnian system with its Cassini Saturn Orbiter and Huygens Titan Probe. Cassini was launched aboard a Titan IV/Centaur 1997 Oct 15.

    (Cassini Home Page from JPL; Huygens Home Page; another Cassini page from JPL)


    StardustScheduled for launch in February 1999, Stardust will fly close to a comet and, for the first time ever, bring material from the comets coma back to Earth for analysis by scientists worldwide. Scheduled to fly-by Comet Wild-2 in 2004, return to Earth in 2006.

    (home page)

    (All missions not otherwise labeled are NASA)

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how do space probes work?

  • A space probe is an unpiloted, unmanned device sent to explore space and gather scientific information. A space probe is launched from Earth with a set of scientific instruments and tools used to study the atmosphere and composition of space and other planets, moons, or celestial bodies. A probe may operate far out in space, or it may orbit or land on a planet or a moon. It may make a one-way journey, or it may bring samples and data back to Earth. Most probes transmit data from space by radio. There are different types of space probes because they collect different science information about very different environments. The probes must be able to withstand the various extreme environments to collect data. Humans have been sending space probes into space since the 1950 s. The next generation of probes will study samples taken from comets, asteroids, and eventually Mars.

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the reason we use a space probe


  • the reason we use a space probe is because we have to see what is going on in space.
  • to see what is going on in space.
  • to see what is new in space.

    Space probes carry instruments into space to make measurements that cannot be made on Earth. Temperature, spectrum, magnetic fields and radiation comprise just a few of the types of phenomena measured. Space probes ride atop a rocket and then separate and set a course based on instructions from Earth-based operators and Pre-Programmed instructions on board. On arrival, the instruments start taking measurements and transmitting them back to Earth.

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    • How many miles do you have to go up to get out of the Earth's atmosphere and into space?

    • What equipment is needed for space travel?

    • How long did it take Neil Armstrong to get to the moon?

      Full Answer

      Space probes typically carry an instrument package based on the mission, communication equipment to transmit the data and a guidance system. On-board power comes from batteries or fuel cells for short missions, solar panels for researching the inner planets or a small nuclear reactor for travel to the outer planets. Once launched, space probes travel to their destination on their own momentum. In some cases, a gravitational slingshot can help accelerate the probe by using the attractive force of another body, such as a moon, to pull the probe toward its destination.

      On arrival, space probes can fly by their destination, making observations as they travel, go into orbit or descend to the surface. Sometimes, a probe orbits for a period of time and then, as its mission ends, it crashes into the planet, transmitting data until it is destroyed.

      Because they are unmanned, space probes have some real advantages. They can measure data in very hostile environments, such as the hot surface of Venus or the methane lakes on Titan, Saturn's largest moon. They can make very long voyages without critical life support resources, such as oxygen, water and food.

      Early space probes launched in the 1950s took measurements around the Earth and moon. In the early 1960s, space probes explored Venus and Mars, giving Earth observers their first real data about these planets. Space probes to the large outer planets, launched in the 1970s, made a number of significant discoveries. Voyager 1, launched in 1977, first explored Jupiter and Saturn, and then was guided to explore deep space. It still transmits data as it travels beyond the solar system. In the 1980s, new space probes orbited the outer planets and their moons for extended study, sending back thousands of pictures along with other physical data for analysis.



    After 35 years of space travel, the twin Voyager planetary probes are nearing the very edge of Earth’s solar system. They will become the first man-made objects to travel between the stars. - See more at: http://www.space.com/17458-voyager-spacecraft-explained-solar-system-infographic.html#sthash.9aw4VDbE.dpuf

    After 35 years of space travel, the twin Voyager planetary probes are nearing the very edge of Earth’s solar system. They will become the first man-made objects to travel between the stars. - See more at: http://www.space.com/17458-voyager-spacecraft-explained-solar-system-infographic.html#sthash.9aw4VDbE.dpuf

    After 35 years of space travel, the twin Voyager planetary probes are nearing the very edge of Earth’s solar system. They will become the first man-made objects to travel between the stars. - See more at: http://www.space.com/17458-voyager-spacecraft-explained-solar-system-infographic.html#sthash.9aw4VDbE.dpuf

space probes