A flyby () is a

spaceflight Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in ...

operation in which a

spacecraft 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, ...

passes in proximity to another body, usually a target of its

space exploration Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by uncrewed robo ...

mission and/or a source of a

gravity assist In orbital mechanics and aerospace engineering, a gravitational slingshot, gravity assist maneuver, or swing-by is the use of the relative movement (e.g. orbit around the Sun) and gravity of a planet or other astronomical object to alter the p ...

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 An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

flybys of Earth for example. Important parameters are the time and distance of closest approach.

Spacecraft flyby

Flyby maneuvers can be conducted with a

planet A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...

, a

natural satellite A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are often colloquially referred to as ''moons'' ...

or a non-planetary object such as a

small Solar System body A small Solar System body (SSSB) is an object in the Solar System that is neither a planet, a dwarf planet, nor a natural satellite. The term was first defined in 2006 by the International Astronomical Union (IAU) as follows: "All other obje ...

. Planetary flybys have occurred with

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

for example: *

List of Earth flybys List of Earth flybys is a list of cases where spacecraft incidentally performed Earth flybys, typically for a gravity assist to another body. See also * List of Solar System probes * Gravity assist * Planetary flyby * Mars flyby A Mars flyby ...

* Mars flyby An example of a comet flyby is when

International Cometary Explorer The International Cometary Explorer (ICE) spacecraft (designed and launched as the International Sun-Earth Explorer-3 (ISEE-3) satellite), was launched 12 August 1978, into a heliocentric orbit. It was one of three spacecraft, along with the mo ...

(formerly ISEE-3) passed about from the

nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: * Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucl ...

of Comet Giacobini-Zinner in September 1985. Another application of the flyby is of Earth's Moon, usually called a lunar flyby. The

Apollo 13 Apollo 13 (April 1117, 1970) was the seventh crewed mission in the Apollo space program and the third meant to land on the Moon. The craft was launched from Kennedy Space Center on April 11, 1970, but the lunar landing was aborted aft ...

spacecraft had an exploded oxygen tank, and therefore had to flyby around the Moon. The

Artemis 2 Artemis 2 (officially Artemis II) is the second scheduled mission of NASA's Artemis program, and the first scheduled crewed mission of NASA's Orion spacecraft, currently planned to be launched by the Space Launch System (SLS) in May 2024. The c ...

and ''#

dearMoon project The ''dearMoon'' project is a lunar tourism mission and art project conceived and financed by Japanese billionaire Yusaku Maezawa. It will make use of a SpaceX Starship spacecraft on a private spaceflight flying a single circumlunar trajectory ...

'' will include a lunar flyby.

Mars

In regards to Mars flybys, a related concept is a Mars flyby rendezvous, where a spacecraft does not enter orbit but rendezvous before or after a flyby of the planet with another spacecraft. Mars flyby rendezvous was evaluated at NASA's

Manned Spacecraft Center The Lyndon B. Johnson Space Center (JSC) is NASA's center for human spaceflight (originally named the Manned Spacecraft Center), where human spaceflight training, research, and flight control are conducted. It was renamed in honor of the late U ...

in the 1960s. At that time NASA developed designs for a combination of a Mars lander, short-stay surface habitat, and ascent vehicle called a

Mars Excursion Module The Mars Excursion Module (MEM) was a spacecraft proposed by NASA in the 1960s for use in a human mission to Mars, and this can refer to any number of studies by corporations and spaceflight centers for Mars landers. However, primarily a MEM ref ...

(MEM); the ascent stage performed the rendezvous with a different spacecraft that did a flyby of Mars without entering orbit or landing. Compared to MOR, a flyby rendezvous means one spacecraft does not have to orbit Mars, so the resources needed on a return journey to Earth are not taken in and out of Mars orbit for example. (See also

Mars cycler A Mars cycler (or Earth–Mars cycler) is a kind of spacecraft trajectory that encounters Earth and Mars regularly. The term Mars cycler may also refer to a spacecraft on a Mars cycler trajectory. The Aldrin cycler is an example of a Mars cycle ...

)

Mariner IV Mariner 4 (together with Mariner 3 known as Mariner-Mars 1964) was the fourth in a series of spacecraft intended for planetary exploration in a flyby mode. It was designed to conduct closeup scientific observations of Mars and to transmit thes ...

flyby of Mars in July 1965 returned more accurate atmospheric data about Mars and much closer views of its surface then previously. Mariner 6 and Mariner 7 flyby of Mars in 1969 caused another breakthrough in knowledge about the planet. The Mariner 6 & 7 infrared radiometer results from he flyby showed that the

atmosphere of Mars The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...

was composed mostly of carbon dioxide (CO₂), and they were also able to detect trace amounts water on the surface of Mars. In 2018, the twin

Mars Cube One Mars Cube One (or MarCO) was a Mars flyby mission launched on 5 May 2018 alongside NASA's ''InSight'' Mars lander. It consisted of two nanospacecraft, MarCO-A and MarCO-B, that provided real-time communications to Earth for ''InSight'' duri ...

performed a flyby to relay communication for

InSight Insight is the understanding of a specific cause and effect within a particular context. The term insight can have several related meanings: *a piece of information *the act or result of understanding the inner nature of things or of seeing intui ...

lander EDL (they were launched towards Mars with the cruise stage carrying the InSight lander). Both MarCOs reached Mars and successfully relayed data during the Entry, Descent, and Landing phase of Insight on November 26, 2018. Meanwhile, '' Tianwen-1 Deployable Camera'', imaged Tianwen-1 in on its transit to Mars, in September 2020 and made a flyby of Mars around 10 February, 2021 according to its trajectory thought for Mars, before entering the deep space or a solar orbit.

Kuiper belt

The ''

New Horizons ''New Horizons'' is an interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a ...

'' spacecraft was planning to fly by the

Kuiper belt The Kuiper belt () is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 tim ...

object

486958 Arrokoth Arrokoth (minor-planet designation 486958 Arrokoth; provisional designation ), formerly nicknamed Ultima Thule, is a trans-Neptunian object located in the Kuiper belt. Arrokoth became the farthest and most primitive object in the Solar System ...

on New Year's Day 2019, after its successful flyby of the dwarf planet

Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the S ...

in 2015. On the night of December 31, 2018 to the morning of January 1, 2019

performed the most distant flyby to date, of the Kuiper belt object Arrokoth. New Horizons previously did a flyby of Pluto in July 2015, and that was at about 32.9 AU (

astronomical units The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits ...

) from the Sun, while the New Year's Day 2019 flyby of the Kuiper object Arrokoth was at 43.6 AU. New Horizons Pluto approach diagram

''Cassini''

'' Cassini-Huygens'' (launched 1997), which orbited

Saturn 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 of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

(from 2004-2017) performed flybys of many of Saturn's moons including

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...

. ''Cassini-Huygen''s had its first flyby of Titan in October 2004. For further examples of ''Cassini'' flybys of Saturn's moons see Timeline of ''Cassini-Huygens''. Cassini conducted many flybys at various distances of the

moons of Saturn The moons of Saturn are numerous and diverse, ranging from tiny moonlets only tens of meters across to enormous Titan, which is larger than the planet Mercury. Saturn has 83 moons with confirmed orbits that are not embedded in its rings—of ...

. It achieved 126 flybys of Titan, and its final close flyby was on April 22, 2017 prior to its retirement. An animation of the ''Cassini'' spacecraft trajectory around Saturn over 10 years, during which it passed closely by many

, is at right.

Comets

(ISEE-3) passed through the plasma tail of comet Giacobini-Zinner doing a flyby of the distance of of the nucleus on September 11, 1985. In 2010, the Deep Impact spacecraft, on the

EPOXI ''EPOXI'' was a compilation of NASA Discovery program missions led by the University of Maryland and principal investigator Michael A'Hearn, with co-operation from the Jet Propulsion Laboratory and Ball Aerospace. ''EPOXI'' uses the '' Deep Imp ...

mission did a flyby of comet Hartley 2.

Natural flyby

PIA21597 - New Radar Images of Asteroid 2014 JO25 (cropped)

Flyby is also sometimes loosely used to describe when, for example, an asteroid approaches and coasts by the Earth. This was also the term for when a comet did a flyby of Mars in 2014. P/2016 BA14 was radar imaged at distance of from Earth in 2016, during its flyby. This enabled the size of the nucleus to be calculated to about in diameter. On December 16, 2018 the

short period The dynamic stability of an aircraft refers to how the aircraft behaves after it has been disturbed following steady non-oscillating flight. Longitudinal modes Oscillating motions can be described by two parameters, the period of time require ...

comet

46P/Wirtanen 46P/Wirtanen is a small short-period comet with a current orbital period of 5.4 years. It was the original target for close investigation by the ''Rosetta'' spacecraft, planned by the European Space Agency, but an inability to meet the launch ...

had its closest approach of Earth, coming within (one of its closest approaches to Earth).

References

External links

Smithsonian Air and Space- Probes and Fly-by Spacecraft
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