Space probe

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Abandoned 1974 probe, Pioneer H, on display in the National Air and Space Museum Pioneer H.JPG
Abandoned 1974 probe, Pioneer H, on display in the National Air and Space Museum
Diagram of extant Solar System missions (see Reference for most recent version) What's Up in the Solar System, active space probes 2019-07.png
Diagram of extant Solar System missions (see Reference for most recent version)

A space probe is a robotic spacecraft that does not orbit Earth, but instead, explores further into outer space. [2] A space probe may approach the Moon; travel through interplanetary space; flyby, orbit, or land on other planetary bodies; or enter interstellar space.


The space agencies of the USSR (now Russia and Ukraine), the United States, the European Union, Japan, China, India, and Israel have collectively launched probes to several planets and moons of the Solar System, as well as to a number of asteroids and comets. Approximately 15 missions are currently operational. [3]

Interplanetary trajectories

Once a probe has left the vicinity of Earth, its trajectory will likely take it along an orbit around the Sun similar to the Earth's orbit. To reach another planet, the simplest practical method is a Hohmann transfer orbit. More complex techniques, such as gravitational slingshots, can be more fuel-efficient, though they may require the probe to spend more time in transit. Some high Delta-V missions (such as those with high inclination changes) can only be performed, within the limits of modern propulsion, using gravitational slingshots. A technique using very little propulsion, but requiring a considerable amount of time, is to follow a trajectory on the Interplanetary Transport Network. [4]

Some notable probes

Luna 9

First man-made object to soft land on the Moon, or any other extra terrestrial surface. [5]

Luna 3

First mission to photograph the far side of the Moon, launched in 1959.

Luna 16

First robotic sample return probe from the Moon.

Lunokhod 1

First rover on Moon. It was sent to the Moon on November 10, 1970.

Mariner 10

First probe to Mercury.

Venera 4

First successful in-place analysis of another planet. It may have also been the first space probe to impact the surface of another planet, although it is unclear whether it reached Venus' surface. [6]

Venera 7

The Venera 7 probe was the first spacecraft to successfully soft land on another planet (Venus) and to transmit data from there back to Earth.

Mariner 9

Upon its arrival at Mars on November 13, 1971, Mariner 9 became the first space probe to maintain orbit around another planet. [7]

The Huygens landing site on Titan Huygens surface color.jpg
The Huygens landing site on Titan

Mars 3

First soft landing on Mars (December 2, 1971 [8] ) The lander began transmitting to the Mars 3 orbiter 90 seconds after landing. After 20 seconds, transmission stopped for unknown reasons. [8]


First successful rover on Mars. [9]

Spirit and Opportunity

The Mars Exploration Rovers, Spirit and Opportunity landed on Mars to explore the Martian surface and geology, and searched for clues to past water activity on Mars. They were each launched in 2003 and landed in 2004. Communication with Spirit stopped on sol 2210 (March 22, 2010). [10] [11] JPL continued to attempt to regain contact until May 24, 2011, when NASA announced that efforts to communicate with the unresponsive rover had ended. [12] [13] [14] Opportunity arrived at Endeavour crater on 9 August 2011, at a landmark called Spirit Point named after its rover twin, after traversing 13 miles (21 km) from Victoria crater, over a three-year period. [15] After a planet wide dust storm in June 2018, the final communication was received on June 10, 2018, and Opportunity was declared dead on February 13, 2019. The rover lasted for almost fifteen years on Mars although the rover was intended to last only three months. [16]

Halley Armada

The first dedicated missions to a comet; in this case, to Halley's Comet during its 1985–86 journey through the inner Solar System. It was also the first massive international coordination of space probes on an interplanetary mission, with probes specifically launched by the Soviet (now Russian) Space Agency, European Space Agency, and Japan's ISAS (now integrated with NASA to JAXA).


Originally a solar observatory in the International Sun-Earth Explorer series, it was sent into solar orbit to make the first close observations of a comet, Comet Giacobini–Zinner, in 1985 as a prelude to studies of Halley's Comet.


Two Russian/French spacecraft. They dropped landers and balloons (first weather balloons deployed on another planet) at Venus before their rendezvous with Halley's Comet.


This Japanese probe was the first non-US, non-Soviet interplanetary probe.[ citation needed ]


A second Japanese probe, it made ultraviolet wavelength observations of the comet.[ clarification needed ]


The first space probe to penetrate a comet's coma and take close-up images of its nucleus.


First solar wind sample return probe from sun-earth L1. [17]


First sample return probe from a comet tail.

NEAR Shoemaker

First probe to land on an asteroid.


First sample return probe to launch from an asteroid.


The Rosetta space probe flew by two asteroids and made a rendezvous and orbited comet 67P/Churyumov-Gerasimenko in November 2014. [18]

Pioneer 10

First probe to Jupiter. Radio communications were lost with Pioneer 10 on January 23, 2003, because of the loss of electric power for its radio transmitter, with the probe at a distance of 12 billion kilometers (80 AU) from Earth.

Pioneer 11

First probe to fly by Saturn. (Communications were later lost due to power constraints and vast distance.)

Voyager 1

Voyager 1's view of Solar System (artist's impression). Voyager 1's view of Solar System (artist's impression).jpg
Voyager 1's view of Solar System (artist's impression).

Voyager 1 is a 733-kilogram probe launched September 5, 1977. It visited Jupiter and Saturn and was the first probe to provide detailed images of the moons of these planets.

Voyager 1 is the farthest human-made object from Earth, traveling away from both the Earth and the Sun at a relatively faster speed than any other probe. [20] As of September 12, 2013, Voyager 1 is about 12 billion miles (19 billion kilometers) from the Sun. [21]

On August 25, 2012, Voyager 1 became the first human made object to enter interstellar space. [22] Voyager 1 has not had a functioning plasma sensor since 1980, but a solar flare in 2012 allowed scientists from NASA to measure vibrations of the plasma surrounding the craft. The vibrations allowed scientists to measure the plasma to be much denser than measurements taken in the far layers of our heliosphere, thus concluding the craft had broken beyond the heliopause.

Voyager 2

Voyager 2 was launched by NASA on August 20, 1977. The probe's primary mission was to visit the ice giants, Uranus and Neptune, which it completed on October 2, 1989. It is currently the only probe to have visited the ice giants. It is the fourth of five spacecraft to have left the solar system. It has been operational for 41 years and 2 months as of October 20, 2018.


Cassini–Huygens was a 5,712-kg (12,593-lb) space probe designed to study gas giant Saturn, along with its ringed system and moons. The NASA probe was launched with ESA lander Huygens on October 1, 1997 from Cape Canaveral. The Cassini probe entered Saturn orbit on July 1, 2004, and Huygens landed on Titan, Saturn's largest moon, on January 14, 2005. [23] On September 15, 2017, the probe was de-orbited and burned up in Saturn's atmosphere, after almost 20 years in space.

New Horizons

First probe to be launched to Pluto. Launched on January 19, 2006, it flew by the Pluto–Charon system on July 14, 2015. [24]


First spacecraft to visit and orbit a protoplanet (4 Vesta), entering orbit on July 16, 2011. [25] [26] Entered orbit around dwarf planet Ceres in early 2015. Currently orbiting Ceres as of February 2017.


First probe to Jupiter without atomic batteries, [27] launched August 8, 2011.

Chang'e 2

Chang'e 2 was deployed to orbit the Moon, visit Sun–Earth L2 Lagrangian point, and make a flyby of asteroid 4179 Toutatis.[ citation needed ]

Beyond the Solar System

Along with Pioneer 10 , Pioneer 11 , and its sister space probe Voyager 2 , Voyager 1 is now an interstellar probe. Voyager 1 and 2 have both achieved solar escape velocity, meaning that their trajectories will not return them to the Solar System. [28] [29]

Probe imagers

Examples of space probe imaging telescope/cameras (focused on visible spectrum).

Name Aperture
cm (in.)
Type WhereWhen
Mars Reconnaissance Orbiter HiRISE 50 cm (19.7″) R/C Mars orbit2005
Mars Global Surveyor MOC [30] 35 cm (13.8″) R/C Mars orbit1996–2006
New Horizons LORRI[ citation needed ]20.8 cm (8.2″) R/C Space (33+ AU from Earth)2006
Lunar Reconnaissance Orbiter LROC-NAC [31] 19.5 cm (7.68″)ReflectorLunar orbit2009
Cassini ISS-NAC [32] 19 cm (7.5″)ReflectorSaturn orbit2004–2017
Galileo – Solid State Imager [33] 17.65 cm (6.95″) Reflector Jupiter1989–2003
Voyager 1/2, ISS-NAC [34] 17.6 cm (6.92″) Catadioptric Space1977
Mariner 10 – TV Photo Experiment (x2) [35] 15 cm (5.9″) Reflector Space1973–1975
Deep Space 1 MICAS [36] 10 cm ( 3.94″)ReflectorSolar orbit1998–2001
Voyager 1/2, ISS-WAC [34] 6 cm (2.36″)LensSpace1977
Cassini ISS-WAC [32] 5.7 cm (2.2″)LensSaturn orbit2004–2017
MESSENGER MDIS-WAC [37] 3 cm (1.18″) Lens Mercury orbit2004–2015
MESSENGER MDIS-NAC [38] 2.5 cm (0.98″)R/CMercury orbit2004–2015
Dawn Framing Camera (FC1/FC2) [39] 2 cm (0.8″)LensAsteroid belt2007–2018

Image forming systems on space probes typically have a multitude of specifications, but aperture can be useful because it constrains the best diffraction limit and light gathering area.[ citation needed ]

See also

Related Research Articles

Interplanetary spaceflight Spacecraft travel between planets of the Solar System

Interplanetary spaceflight or interplanetary travel is travel between planets, usually within a single planetary system. In practice, spaceflights of this type are confined to travel between the planets of the Solar System.

Space exploration Discovery and exploration of outer space

Space exploration is the use of astronomy and space technology to explore outer space. While the study of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by unmanned robotic space probes and human spaceflight.

<i>Voyager 1</i> Planetary space probe; farthest human-made object from Earth

Voyager 1 is a space probe that was 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 42 years, 6 months and 15 days as of March 21, 2020, the spacecraft still communicates with the Deep Space Network to receive routine commands and to transmit data to Earth. Real-time distance and velocity data is provided by NASA and JPL. At a distance of 148.61 AU from Earth as of March 12, 2020, it is the most distant man-made object from Earth.

<i>Voyager 2</i> Space probe and the second-farthest man-made object from Earth

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. Voyager 2 is the fourth of five spacecraft to achieve the Solar escape velocity, which will allow it to leave the Solar System.

Spacecraft Crewed or uncrewed vehicle designed to fly in outer space

A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle.

Timeline of Solar System astronomy timeline

Timeline of Solar System astronomy

Gravity assist space maneuver

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.

Uncrewed spacecraft spacecraft without people on board

Uncrewed or unmanned spacecraft are spacecraft without people on board, used for robotic spaceflight. Uncrewed spacecraft may have varying levels of autonomy from human input; they may be remote controlled, remote guided or even autonomous, meaning they have a pre-programmed list of operations, which they will execute unless otherwise instructed.

Discovery Program NASAs space exploration missions

The Discovery Program is a series of Solar System exploration missions funded by the US National Aeronautics and Space Administration (NASA) through its Planetary Missions Program Office. Each mission has a cost cap, at a lower level than a mission from NASA's New Frontiers or Flagship Programs. As a result, Discovery missions tend to be more focused on a specific scientific goal.

Mariner Mark II

Mariner Mark II was NASA's planned family of unmanned spacecraft for the exploration of the outer Solar System that were to be developed and operated by JPL between 1990 through the year 2010.

Outline of space exploration Overview of and topical guide to space exploration

The following outline is provided as an overview of and topical guide to space exploration:

Discovery and exploration of the Solar System

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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

Planetary Science Decadal Survey

The Planetary Science Decadal Survey is a publication of the United States National Research Council produced for NASA and other United States Government Agencies such as the National Science Foundation. The document identifies key questions facing planetary science and outlines recommendations for space and ground-based exploration ten years into the future. Missions to gather data to answer these big questions are described and prioritized, where appropriate. Similar Decadal Surveys cover Astronomy and Astrophysics, Earth Science and Heliophysics.

Flyby (spaceflight) flight event at some distance from the object

A flyby is a spaceflight operation in which a spacecraft passes in close proximity to another body, usually a target of its space exploration mission and/or a source of a gravity assist to impel it towards another target. Spacecraft which are specifically designed for this purpose are known as flyby spacecraft, although the term has also been used in regard to asteroid flybys of Earth for example. Important parameters are the time and distance of closest approach.


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Further reading