Juno (mission)
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''Juno'' is a
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
space probe Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...
orbiting the planet
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
. Built by
Lockheed Martin The Lockheed Martin Corporation is an American Arms industry, defense and aerospace manufacturer with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta on March 15, 1995. It is headquartered in North ...
and operated by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center (FFRDC) in La Cañada Flintridge, California, Crescenta Valley, United States. Founded in 1936 by Cali ...
, the spacecraft was launched from
Cape Canaveral Air Force Station Cape Canaveral Space Force Station (CCSFS) is an installation of the United States Space Force's Space Launch Delta 45, located on Cape Canaveral in Brevard County, Florida. Headquartered at the nearby Patrick Space Force Base, the sta ...
on August 5, 2011
UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...
, as part of the
New Frontiers program The New Frontiers program is a series of space exploration missions being conducted by NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the ...
. ''Juno'' entered a
polar orbit A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of abo ...
of Jupiter on July 5, 2016, UTC, to begin a scientific investigation of the planet. After completing its mission, ''Juno'' was originally planned to be intentionally deorbited into Jupiter's atmosphere, but has since been approved to continue orbiting until contact is lost with the spacecraft. ''Juno'' mission is to measure Jupiter's composition,
gravitational field In physics, a gravitational field or gravitational acceleration field is a vector field used to explain the influences that a body extends into the space around itself. A gravitational field is used to explain gravitational phenomena, such as ...
,
magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
, and polar magnetosphere. It also searches for clues about how the planet formed, including whether it has a rocky core, the amount of water present within the deep atmosphere,
mass distribution In physics and mechanics, mass distribution is the spatial distribution of mass within a solid body. In principle, it is relevant also for gases or liquids, but on Earth their mass distribution is almost homogeneous. Astronomy In astronomy mass ...
, and its deep winds, which can reach speeds up to . ''Juno'' is the second spacecraft to orbit Jupiter, after the nuclear powered ''Galileo'' orbiter, which orbited from 1995 to 2003. Unlike all earlier spacecraft sent to the
outer Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sol ...
and beyond—which used
radioisotope thermoelectric generator A radioisotope thermoelectric generator (RTG, RITEG), or radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the Decay heat, heat released by the decay of a suitable radioactive material i ...
s for power—''Juno'' is powered by
solar panel A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...
s, more commonly used by satellites orbiting Earth and working in the
inner Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sol ...
. Accordingly, ''Juno'' required the three largest solar panel wings ever deployed on a planetary probe (at the time of launching). These play an integral role in stabilizing the spacecraft as well as generating power.


Naming

A NASA compilation of mission names and acronyms referred to the mission by the
backronym A backronym is an acronym formed from an already existing word by expanding its letters into the words of a phrase. Backronyms may be invented with either serious or humorous intent, or they may be a type of false etymology or folk etymology. The ...
''Jupiter Near-polar Orbiter''. However the project itself has consistently described it as a name with mythological associations and not an acronym. The spacecraft's current name is in reference to the Roman goddess
Juno Juno commonly refers to: *Juno (mythology), the Roman goddess of marriage and queen of the gods * ''Juno'' (film), the 2007 film Juno may also refer to: Arts, entertainment and media Fictional characters *Juno, a character in the book ''Juno of ...
. ''Juno'' is sometimes called the ''New Frontiers 2'' as the second mission in the New Frontiers program, but is not to be confused with
New Horizons 2 ''New Horizons 2'' (also ''New Horizons II'', NHII, or NH2) was a proposed mission to the trans-Neptunian objects by NASA. It was conceived as a planetary flyby mission in 2002, based on the ''New Horizons'' spacecraft, which was in developmen ...
, a proposed but unselected New Frontiers mission.


Overview

''Juno'' was selected on June 9, 2005, as the next New Frontiers mission after ''
New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...
''. The desire for a Jupiter probe was strong in the years prior to this, but there had not been any approved missions. The
Discovery Program The Discovery Program is a series of Solar System exploration missions funded by the U.S. National Aeronautics and Space Administration (NASA) through its Planetary Missions Program Office. The cost of each mission is capped at a lower level t ...
had passed over the somewhat similar but more limited Interior Structure and Internal Dynamical Evolution of Jupiter (INSIDE Jupiter) proposal, and the turn-of-the-century era
Europa Orbiter The Europa Orbiter was a planned NASA mission to Jupiter's Moon Europa, that was cancelled in 2002. Its main objectives included determining the presence or absence of a subsurface ocean and identifying candidate sites for future lander mis ...
was canceled in 2002. The flagship-level
Europa Jupiter System Mission Europa may refer to: Places * Europa (Roman province), a province within the Diocese of Thrace * Europa (Seville Metro), Seville, Spain; a station on the Seville Metro * Europa City, Paris, France; a planned development * Europa Cliffs, Alexan ...
was in the works in the early 2000s, but funding issues resulted in it evolving into ESA's
Jupiter Icy Moons Explorer The Jupiter Icy Moons Explorer (Juice, formerly JUICE) is an interplanetary spacecraft on its way to orbit and study three icy moons of Jupiter (planet), Jupiter: Ganymede (moon), Ganymede, Callisto (moon), Callisto, and Europa (moon), Europa ...
. ''Juno'' completed a five-year cruise to Jupiter, arriving on July 5, 2016. The spacecraft traveled a total distance of roughly to reach Jupiter. The spacecraft was designed to orbit Jupiter 37 times over the course of its mission. This was originally planned to take 20 months. ''Juno'' trajectory used a
gravity assist A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational slingshot in orbital mechanics, is a type of spaceflight flyby (spaceflight), flyby which makes use of the relative movement (e.g. orbit around the Sun) and gra ...
speed boost from Earth, accomplished by an Earth flyby in October 2013, two years after its launch on August 5, 2011. The spacecraft performed an orbit insertion burn to slow it enough to allow capture. It was expected to make three 53-day orbits before performing another burn on December 11, 2016, that would bring it into a 14-day
polar orbit A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of abo ...
called the Science Orbit. Because of a suspected problem in ''Juno'' main engine, the burn scheduled on December 11, 2016, was cancelled and ''Juno'' remained in its 53-day orbit until the first Ganymede encounter of its Extended Mission. This extended mission began with a flyby of Ganymede on June 7, 2021. Subsequent flybys of Europa and then Io decreased the orbital period to 33 days by February 2024. During the science mission,
infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
and
microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...
instruments will measure the thermal radiation emanating from deep within
Jupiter's atmosphere 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, am ...
. These observations will complement previous studies of its composition by assessing the abundance and distribution of water, and therefore oxygen. This data will provide insight into Jupiter's origins. ''Juno'' will also investigate the
convection Convection is single or Multiphase flow, multiphase fluid flow that occurs Spontaneous process, spontaneously through the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoy ...
that drives natural circulation patterns in Jupiter's atmosphere. Other instruments aboard ''Juno'' will gather data about its gravitational field and polar
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
. The ''Juno'' mission was planned to conclude in February 2018 after completing 37 orbits of Jupiter, but now has been commissioned through 2025 to do a further 42 additional orbits of Jupiter as well as close flybys of Ganymede, Europa and Io. The probe was then intended to be deorbited and burnt up in Jupiter's outer atmosphere to avoid any possibility of impact and biological contamination of one of its moons.


Flight trajectory


Launch

''Juno'' was launched atop an
Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to ...
( 551 configuration) at
Cape Canaveral Air Force Station Cape Canaveral Space Force Station (CCSFS) is an installation of the United States Space Force's Space Launch Delta 45, located on Cape Canaveral in Brevard County, Florida. Headquartered at the nearby Patrick Space Force Base, the sta ...
(CCAFS),
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
on August 5, 2011, 16:25:00 UTC. The Atlas V (AV-029) used a Russian-built
RD-180 The RD-180 () is a rocket engine that was designed and built in Russia. It features a dual combustion chamber, dual-nozzle design and is fueled by a RP-1/ LOX mixture. The RD-180 is derived from the RD-170 line of rocket engines, which were use ...
main engine, powered by
kerosene Kerosene, or paraffin, is a combustibility, combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in Aviation fuel, aviation as well as households. Its name derives from the Greek (''kērós'') meaning " ...
and
liquid oxygen Liquid oxygen, sometimes abbreviated as LOX or LOXygen, is a clear cyan liquid form of dioxygen . It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an application which is ongoing. Physical ...
. The main engine ignited and underwent checkout then, 3.8 seconds later, the five strap-on
solid rocket booster A solid rocket booster (SRB) is a solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and Space Shuttle, have used SRBs to give laun ...
s (SRBs) ignited. Following the SRB burnout, about 93 seconds into the flight, two of the spent boosters fell away from the vehicle, followed 1.5 seconds later by the remaining three. When heating levels had dropped below predetermined limits, the
payload fairing A payload fairing or nose fairing is a nose cone used to protect a launch vehicle, spacecraft payload (air and space craft), payload against the impact of dynamic pressure and aerodynamic heating during launch through an atmosphere. An additiona ...
that protected ''Juno'' during launch and transit through the thickest part of the atmosphere separated, about 3 minutes 24 seconds into the flight. The Atlas V main engine cut off 4 minutes 26 seconds after liftoff. Sixteen seconds later, the Centaur second stage ignited, and it burned for about 6 minutes, putting the satellite into an initial
parking orbit A parking orbit is a temporary orbit used during the launch of a spacecraft. A launch vehicle follows a trajectory to the parking orbit, then coasts for a while, then engines fire again to enter the final desired trajectory. An alternative trajec ...
. The vehicle coasted for about 30 minutes, and then the Centaur was reignited for a second firing of 9 minutes, placing the spacecraft on an
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
escape trajectory in a
heliocentric orbit A heliocentric orbit (also called circumsolar orbit) is an orbit around the barycenter of the Solar System, which is usually located within or very near the surface of the Sun. All planets, comets, and asteroids in the Solar System, and the Sun ...
. Prior to separation, the Centaur stage used onboard
reaction engine A reaction engine is an engine, engine or motor that produces thrust by expelling reaction mass (reaction propulsion), in accordance with Newton's third law of motion. This law of motion is commonly paraphrased as: "For every action force there ...
s to spin ''Juno'' up to 1.4 r.p.m. About 54 minutes after launch, the spacecraft separated from the Centaur and began to extend its
solar panel A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...
s. Following the full deployment and locking of the solar panels, ''Juno'' batteries began to recharge. Deployment of the solar panels reduced ''Juno'' spin rate by two-thirds. The probe is spun to ensure stability during the voyage and so that all instruments on the probe are able to observe Jupiter.Juno Mission Profile & Timeline
The voyage to Jupiter took five years, and included two orbital maneuvers in August and September 2012 and a flyby of the Earth on October 9, 2013. When it reached the
Jovian system There are 97 moons of Jupiter with confirmed orbits . This number does not include a number of meter-sized moonlets thought to be shed from the inner moons, nor hundreds of possible kilometer-sized outer irregular moons that were only briefl ...
, ''Juno'' had traveled approximately . File:Atlas V with Juno on CCAFS SLC-41 (PIA14416).jpg, Atlas V on launch pad File:Juno Lifts Off.jpg, Lift-off File:Launch of Juno 2011.ogv, Launch video


Deep Space Maneuvers and flyby of the Earth

After traveling for about a year in an elliptical heliocentric orbit, ''Juno'' performed two Deep Space Maneuvers (DSMs), firing its engine twice near
aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...
(beyond the orbit of
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
) to change its orbit and return to pass by the
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
at a distance of 559 kilometers in October 2013. The combination of the DSMs and the resulting Earth flyby helped Juno slingshot itself toward the Jovian system in a maneuver called a
gravity assist A gravity assist, gravity assist maneuver, swing-by, or generally a gravitational slingshot in orbital mechanics, is a type of spaceflight flyby (spaceflight), flyby which makes use of the relative movement (e.g. orbit around the Sun) and gra ...
. The spacecraft received a boost in speed of more than , and it was set on a course to Jupiter. The flyby was also used as a rehearsal for the ''Juno'' science team to test some instruments and practice certain procedures before the arrival at Jupiter.


Insertion into Jovian orbit

Jupiter's gravity accelerated the approaching spacecraft to around . On July 5, 2016, between 03:18 and 03:53
UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...
Earth-received time Spacecraft Event Time (SCET) is the spacecraft-local time for events that happen at the spacecraft. SCET is used for command programs that control the timing of spacecraft operations and to identify when specific events occur on the spacecraft rel ...
, an insertion burn lasting 2,102 seconds decelerated ''Juno'' by and changed its trajectory from a
hyperbolic Hyperbolic may refer to: * of or pertaining to a hyperbola, a type of smooth curve lying in a plane in mathematics ** Hyperbolic geometry, a non-Euclidean geometry ** Hyperbolic functions, analogues of ordinary trigonometric functions, defined u ...
flyby to an elliptical, polar orbit with a period of about 53.5 days. The spacecraft successfully entered Jovian orbit on July 5, 2016, at 03:53 UTC.


Orbit and environment

''Juno'' highly elliptical initial polar orbit takes it within of the planet and out to , far beyond
Callisto CALLISTO (''Cooperative Action Leading to Launcher Innovation in Stage Toss-back Operations'') is a reusable VTVL Prototype, demonstrator propelled by a small 40 kN Japanese LOX-LH2 rocket engine. It is being developed jointly by the CNES, French ...
's orbit. An
eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...
-reducing burn, called the Period Reduction Maneuver, was planned that would drop the probe into a much shorter 14 day science orbit. Originally, ''Juno'' was expected to complete 37 orbits over 20 months before the end of its mission. Due to problems with helium valves that are important during main engine burns, mission managers announced on February 17, 2017, that ''Juno'' would remain in its original 53-day orbit, since the chance of an engine misfire putting the spacecraft into a bad orbit was too high. ''Juno'' completed only 12 science orbits before the end of its budgeted mission plan, ending July 2018. In June 2018, NASA extended the mission through July 2021, as described below. The orbits were carefully planned in order to minimize contact with Jupiter's dense
radiation belt The Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet's magnetosphere. Earth has two such belts, and sometimes others ma ...
s, which can damage spacecraft electronics and solar panels, by exploiting a gap in the radiation envelope near the planet, passing through a region of minimal radiation. The
Juno Radiation Vault Juno Radiation Vault is a compartment inside the '' Juno'' spacecraft that houses much of the probe's electronics and computers, and is intended to offer increased protection of radiation to the contents as the spacecraft endures the radiation ...
, with 1-centimeter-thick
titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
walls (three times as thick as the ''Galileo'' spacecraft body's), also aids in protecting ''Juno'' electronics by reducing the incoming radiation by a factor of 800. Despite the intense radiation, JunoCam and the Jovian Infrared Auroral Mapper (JIRAM) were designed to endure at least eight orbits, while the Microwave Radiometer (MWR) was made to endure at least eleven orbits. All instruments are operational as of perijove 71. Although the flux of electrons close to Jupiter is about ten times as high as it is around Jupiter's moon Europa, ''Juno'' will still receive a lower total dose of radiation in its polar orbit (20
Mrad The Barrett MRAD (Multi-role Adaptive Design) is a bolt-action sniper rifle designed by Barrett to meet the requirements of the SOCOM PSR. The MRAD is based on the Barrett 98B and includes a number of modifications and improvements. The Barre ...
through end of mission) than the ''Galileo'' orbiter received in its equatorial orbit. ''Galileo'' subsystems were damaged by radiation during its mission, including an LED in its data recording system.


Orbital operations

The spacecraft completed its first flyby of Jupiter (
perijove An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides pertai ...
1) on August 26, 2016, and captured the first images of the planet's north pole. On October 14, 2016, days prior to perijove 2 and the planned Period Reduction Maneuver, telemetry showed that some of ''Juno'' helium valves were not opening properly. On October 18, 2016, some 13 hours before its second close approach to Jupiter, ''Juno'' entered into
safe mode Safe mode is a diagnosis, diagnostic mode of a computer operating system (OS). It can also refer to a mode of operation by application software. ''Safe mode'' is intended to help fix most, if not all, problems within an operating system. It is a ...
, an operational mode engaged when its onboard computer encounters unexpected conditions. The spacecraft powered down all non-critical systems and reoriented itself to face the Sun to gather the most power. Due to this, no science operations were conducted during perijove 2. On December 11, 2016, the spacecraft completed perijove 3, with all but one instrument operating and returning data. One instrument, JIRAM, was off pending a flight software update. Perijove 4 occurred on February 2, 2017, with all instruments operating. Perijove 5 occurred on March 27, 2017. Perijove 6 took place on May 19, 2017. Although the mission's lifetime is inherently limited by radiation exposure, almost all of this dose was planned to be acquired during the perijoves. , the 53.4 day orbit was planned to be maintained through July 2018 for a total of twelve science-gathering perijoves. At the end of this prime mission, the project was planned to go through a science review process by NASA's
Planetary Science Division The Science Mission Directorate (SMD) of the National Aeronautics and Space Administration (NASA) is one of the six directorates that constitute NASA. Its responsibility is to define and direct research into scientific questions of interest, shari ...
to determine if it will receive funding for an extended mission. In June 2018, NASA extended the mission operations plan to July 2021. In January 2021, NASA extended the mission operations to September 2025. In this phase ''Juno'' began to examine Jupiter's inner moons, Ganymede,
Europa Europa may refer to: Places * Europa (Roman province), a province within the Diocese of Thrace * Europa (Seville Metro), Seville, Spain; a station on the Seville Metro * Europa City, Paris, France; a planned development * Europa Cliffs, Alexan ...
and Io. A flyby of Ganymede occurred on June 7, 2021, 17:35
UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...
, coming within , the closest any spacecraft has come to the moon since ''
Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 â€“ 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...
'' in 2000. A flyby of Europa took place on September 29, 2022, at a distance of . Juno performed two flybys of Io on December 30, 2023, and February 3, 2024, gathering observational data on volcanic activity. From April 2024, Juno will begin a series of experiments to learn more about Jupiter's interior shape and structure.


Planned deorbit and disintegration

NASA originally planned to
deorbit Atmospheric entry (sometimes listed as Vimpact or Ventry) is the movement of an object from outer space into and through the gases of an atmosphere of a planet, dwarf planet, or natural satellite. Atmospheric entry may be ''uncontrolled entry ...
the spacecraft into the atmosphere of Jupiter after completing 32 orbits of Jupiter, but has since extended the mission to September 2025. The controlled deorbit is intended to eliminate space debris and risks of contamination in accordance with NASA's
planetary protection Planetary protection is a guiding principle in the design of an interplanetary mission, aiming to prevent biological contamination of both the target celestial body and the Earth in the case of sample-return missions. Planetary protection refle ...
guidelines.


Team

Scott Bolton of the
Southwest Research Institute Southwest Research Institute (SwRI), headquartered in San Antonio, Texas, is an independent and nonprofit applied research and development (R&D) organization. Founded in 1947 by oil businessman Tom Slick, it provides contract research and deve ...
in
San Antonio San Antonio ( ; Spanish for " Saint Anthony") is a city in the U.S. state of Texas and the most populous city in Greater San Antonio. San Antonio is the third-largest metropolitan area in Texas and the 24th-largest metropolitan area in the ...
,
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
is the principal investigator and is responsible for all aspects of the mission. The
Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center (FFRDC) in La Cañada Flintridge, California, Crescenta Valley, United States. Founded in 1936 by Cali ...
in
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
manages the mission and the
Lockheed Martin Corporation The Lockheed Martin Corporation is an American defense and aerospace manufacturer with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta on March 15, 1995. It is headquartered in North Bethesda, Ma ...
was responsible for the spacecraft development and construction. The mission is being carried out with the participation of several institutional partners. Coinvestigators include Toby Owen of the
University of Hawaii A university () is an educational institution, institution of tertiary education and research which awards academic degrees in several Discipline (academia), academic disciplines. ''University'' is derived from the Latin phrase , which roughly ...
,
Andrew Ingersoll Andrew Perry Ingersoll (born 1940) is an American physicist. He is a professor of planetary science at the California Institute of Technology. Ingersoll was elected to the American Academy of Arts and Sciences in 1997. He received the lifetime ach ...
of
California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...
, Frances Bagenal of the
University of Colorado at Boulder The University of Colorado Boulder (CU Boulder, CU, or Colorado) is a Public university, public research university in Boulder, Colorado, United States. Founded in 1876, five months before Colorado became a Federated state, state, it is the fla ...
, and Candy Hansen of the
Planetary Science Institute The Planetary Science Institute (PSI) is a 501(c)(3) non-profit research institute based in Tucson, Arizona, focusing on planetary science. , its director is Dr. Mark V. Sykes. PSI, along with Space Science Institute (SSI) Southwest Researc ...
. Jack Connerney of the
Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...
served as instrument lead.


Cost

''Juno'' was originally proposed at a cost of approximately US$700 million (fiscal year 2003) for a launch in June 2009 (equivalent to US$ million in ). NASA budgetary restrictions resulted in postponement until August 2011, and a launch on board an
Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was developed by Lockheed Martin and has been operated by United Launch Alliance (ULA) since 2006. Primarily used to ...
rocket in the 551 configuration. the mission was projected to cost US$1.46 billion for operations and data analysis through 2022.


Scientific objectives

The ''Juno'' spacecraft's suite of science instruments will: * Determine the ratio of
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
to
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
, effectively measuring the abundance of water in Jupiter, which will help distinguish among prevailing theories linking Jupiter's formation to the Solar System. * Obtain a better estimate of Jupiter's core mass, which will also help distinguish among prevailing theories linking Jupiter's formation to the Solar System. * Precisely map Jupiter's
gravitational In physics, gravity (), also known as gravitation or a gravitational interaction, is a fundamental interaction, a mutual attraction between all massive particles. On Earth, gravity takes a slightly different meaning: the observed force be ...
field to assess the distribution of mass in Jupiter's interior, including properties of its structure and dynamics. * Precisely map Jupiter's
magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...
to assess the origin and structure of the field, and the depth at which the planet's magnetic field is created. This experiment will also help scientists understand the fundamental physics of
dynamo theory In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convection, convecting, and electrically conductin ...
. * Map the variation in atmospheric composition, temperature, structure, cloud opacity and dynamics to pressures far greater than at all latitudes. * Characterize and explore the three-dimensional structure of Jupiter's polar
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
and
auroras An aurora ( aurorae or auroras), also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in Earth's sky, predominantly observed in high-latitude regions (around the Arc ...
. * Measure the orbital
frame-dragging Frame-dragging is an effect on spacetime, predicted by Albert Einstein's General relativity, general theory of relativity, that is due to non-static stationary distributions of mass–energy. A stationary Field (physics), field is one that is ...
, known also as
Lense–Thirring precession In general relativity, Lense–Thirring precession or the Lense–Thirring effect (; named after Josef Lense and Hans Thirring) is a relativistic correction to the precession of a gyroscope near a large rotating mass such as the Earth. It is ...
caused by the
angular momentum Angular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of Momentum, linear momentum. It is an important physical quantity because it is a Conservation law, conserved quantity â€“ the total ang ...
of Jupiter, and possibly a new test of general relativity effects connected with the Jovian rotation.


Scientific instruments

The ''Juno'' mission's scientific objectives are being achieved with a payload of nine instruments on board the spacecraft:


Microwave radiometer (MWR)

The
microwave radiometer A microwave radiometer (MWR) is a radiometer that measures energy emitted at one millimeter-to-metre wavelengths (frequencies of 0.3–300 GHz) known as microwaves. Microwave radiometers are very sensitive receivers designed to measure thermally ...
comprises six antennas mounted on two of the sides of the body of the probe. They will perform measurements of
electromagnetic waves In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ran ...
on frequencies in the
microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...
range: 600
MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...
, 1.2, 2.4, 4.8, 9.6 and 22 GHz, the only microwave frequencies which are able to pass through the thick Jovian atmosphere. The radiometer will measure the abundance of water and ammonia in the deep layers of the atmosphere up to pressure or deep. The combination of different wavelengths and the emission angle should make it possible to obtain a temperature profile at various levels of the atmosphere. The data collected will determine how deep the atmospheric circulation is. The MWR is designed to function through orbit 11 of Jupiter.


Jovian Infrared Auroral Mapper (JIRAM)

The spectrometer mapper JIRAM, operating in the
near infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those o ...
(between 2 and 5 μm), conducts surveys in the upper layers of the atmosphere to a depth of between where the pressure reaches . JIRAM will provide images of the aurora in the wavelength of 3.4 μm in regions with abundant H3+ ions. By measuring the heat radiated by the atmosphere of Jupiter, JIRAM can determine how clouds with water are flowing beneath the surface. It can also detect
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
,
water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...
,
ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
and
phosphine Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...
. It was not required that this device meets the radiation resistance requirements. The JIRAM instrument is expected to operate through the eighth orbit of Jupiter.
JIRAM's spin-compensation mirror is stuck since PJ44, but the instrument is operational.


Magnetometer (MAG)

The magnetic field investigation has three goals: mapping of the magnetic field, determining the dynamics of Jupiter's interior, and determination of the three-dimensional structure of the polar magnetosphere. The magnetometer experiment consists of the Flux Gate Magnetometer (FGM), which will observe the strength and direction of the magnetic field lines, and the Advanced Stellar Compass (ASC), which will monitor the orientation of the magnetometer sensors.


Gravity Science (GS)

The purpose of measuring gravity by radio waves is to establish a map of the distribution of mass inside Jupiter. The uneven distribution of mass in Jupiter induces small variations in gravity all along the orbit followed by the probe when it runs closer to the surface of the planet. These gravity variations drive small probe velocity changes. The purpose of radio science is to detect the
Doppler effect The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described ...
on radio broadcasts issued by ''Juno'' toward Earth in
Ka-band The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum. The designation "Ka-band" is from Kurz-above, which stems from the German word ''kurz,'' meaning "short". There ...
and
X-band The X band is the designation for a band of frequency, frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is set at approximately 7.0â ...
, which are frequency ranges that can conduct the study with fewer disruptions related to the
solar wind The solar wind is a stream of charged particles released from the Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...
or
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
's
ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays ...
.


Jovian Auroral Distributions Experiment (JADE)

The energetic particle detector JADE will measure the angular distribution, energy, and the velocity vector of ions and electrons at ''low'' energy (ions between 13 eV and 20 KeV, electrons of 200 eV to 40 KeV) present in the aurora of Jupiter. On JADE, like JEDI, the electron analyzers are installed on three sides of the upper plate which allows a measure of frequency three times higher.


Jovian Energetic Particle Detector Instrument (JEDI)

The energetic particle detector JEDI will measure the angular distribution and the velocity vector of ions and electrons at ''high'' energy (ions between 20 keV and 1 MeV, electrons from 40 to 500 keV) present in the polar
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
of Jupiter. JEDI has three identical sensors dedicated to the study of particular ions of
hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
,
helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...
,
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
and
sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
.


Radio and Plasma Wave Sensor (Waves)

This instrument will identify the regions of auroral currents that define Jovian radio emissions and acceleration of the auroral particles by measuring the radio and plasma spectra in the auroral region. It will also observe the interactions between
Jupiter's atmosphere 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, am ...
and
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior Dynamo ...
. The instrument consists of two antennae that detect radio and plasma waves.


Ultraviolet Spectrograph (UVS)

UVS will record the wavelength, position and arrival time of detected
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
photons during the time when the spectrograph slit views Jupiter during each turn of the spacecraft. The instrument will provide spectral images of the UV auroral emissions in the polar magnetosphere.


JunoCam (JCM)

A visible light camera/telescope, included in the payload to facilitate education and public outreach; later re-purposed to study the dynamics of Jupiter's clouds, particularly those at the poles. It was anticipated that it would operate through only eight orbits of Jupiter ending in September 2017 due to the planet's damaging radiation and magnetic field, but as of October 2023 (55 orbits), JunoCam remains operational.


Operational components


Satellite bus

''Juno''
satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are less customized than specially-produced satelli ...
, its main electronics and propulsion box, is a
hexagonal prism In geometry, the hexagonal prism is a Prism (geometry), prism with hexagonal base. Prisms are polyhedrons; this polyhedron has 8 face (geometry), faces, 18 Edge (geometry), edges, and 12 vertex (geometry), vertices.. As a semiregular polyhedro ...
.


Solar panels

''Juno'' is the first mission to Jupiter to use
solar panels A solar panel is a device that converts sunlight into electricity by using photovoltaic (PV) cells. PV cells are made of materials that produce excited electrons when exposed to light. These electrons flow through a circuit and produce direct ...
instead of the
radioisotope thermoelectric generator A radioisotope thermoelectric generator (RTG, RITEG), or radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the Decay heat, heat released by the decay of a suitable radioactive material i ...
s (RTG) used by ''
Pioneer 10 ''Pioneer 10'' (originally designated Pioneer F) is a NASA space probe launched in 1972 that completed the first mission to the planet Jupiter. ''Pioneer 10'' became the first of five artificial objects to achieve the escape velocity needed ...
'', ''
Pioneer 11 ''Pioneer 11'' (also known as ''Pioneer G'') is a NASA robotic space probe launched on April 5, 1973, to study the asteroid belt, the environment around Jupiter and Saturn, the solar wind, and cosmic rays. It was the first probe to Exploration ...
'', the
Voyager program The Voyager program is an American scientific program that employs two interstellar probes, ''Voyager 1'' and ''Voyager 2''. They were launched in 1977 to take advantage of a favorable planetary alignment to explore the two gas giants Jupiter ...
, ''
Ulysses Ulysses is the Latin name for Odysseus, a legendary Greek hero recognized for his intelligence and cunning. He is famous for his long, adventurous journey home to Ithaca after the Trojan War, as narrated in Homer's Odyssey. Ulysses may also refer ...
'', ''
Cassini–Huygens ''Cassini–Huygens'' ( ), commonly called ''Cassini'', was a space research, space-research mission by NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a space probe to study the planet Saturn and its system, i ...
'', ''
New Horizons ''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...
'', and the ''Galileo'' orbiter. It is also the farthest solar-powered trip in the history of space exploration. Once in orbit around Jupiter, ''Juno'' receives only 4% as much sunlight as it would on
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
, but the global shortage of
plutonium-238 Plutonium-238 ( or Pu-238) is a radioactive isotope of plutonium that has a half-life of 87.7 years. Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suitable for usage ...
at the time, as well as advances made in solar cell technology over the past several decades, makes it economically preferable to use solar panels of practical size to provide power at a distance of 5 a.u. from the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
. The ''Juno'' spacecraft uses three solar panels symmetrically arranged around the spacecraft. Shortly after it cleared Earth's atmosphere, the panels were deployed. Two of the panels have four hinged segments each, and the third panel has three segments and a
magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
. Each panel is providing of active cells – the largest on any NASA deep-space probe at the time of launching. The combined mass of the three panels is nearly . If the panels were optimized to operate at Earth, they would produce 12 to 14 kilowatts of power. Only about 486 watts were generated when ''Juno'' arrived at Jupiter, projected to decline to near 420 watts as radiation degrades the cells. The solar panels will remain in sunlight continuously from launch through the end of the mission, except for short periods during the operation of the main engine and eclipses by Jupiter. A central power distribution and drive unit monitors the power that is generated by the solar panels and distributes it to instruments, heaters, and experiment sensors, as well as to batteries that are charged when excess power is available. Two 55 Ah
lithium-ion A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible Intercalation (chemistry), intercalation of Li+ ions into electronically Electrical conductor, conducting solids to store energy. Li-ion batteries are c ...
batteries that are able to withstand the radiation environment of Jupiter provide power when ''Juno'' passes through eclipse.


Telecommunications

''Juno'' uses
in-band signaling In telecommunications, in-band signaling is the sending of control information within the same band or channel used for data such as voice or video. This is in contrast to out-of-band signaling which is sent over a different channel, or even o ...
("tones") for several critical operations as well as status reporting during cruise mode, but it is expected to be used infrequently. Communications are via the and antennas of the
NASA Deep Space Network The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA' ...
(DSN) utilizing an
X-band The X band is the designation for a band of frequency, frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is set at approximately 7.0â ...
direct link. The command and data processing of the ''Juno'' spacecraft includes a flight computer capable of providing about 50 Mbit/s of instrument throughput. Gravity science subsystems use the X-band and Ka-band
Doppler The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. The ''Doppler effect'' is named after the physicist Christian Doppler, who described ...
tracking and autoranging. Due to telecommunications constraints, ''Juno'' will only be able to return about 40 megabytes of JunoCam data during each 11-day orbital period, limiting the number of images that are captured and transmitted during each orbit to somewhere between 10 and 100 depending on the compression level used. The overall amount of data downlinked on each orbit is significantly higher and used for the mission's scientific instruments; JunoCam is intended for public outreach and is thus secondary to the science data. This is comparable to the previous ''Galileo'' mission that orbited Jupiter, which captured thousands of images despite its slow data rate of 1000 bit/s (at maximum compression level) due to the failure of its high gain antenna. The communication system is also used as part of the Gravity Science experiment.


Propulsion

''Juno'' uses a LEROS 1b main engine with
hypergolic propellant A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...
, manufactured by
Moog Inc Moog Inc. ( ) is an American-based designer and manufacturer of electric, electro-hydraulic and hydraulic motion, controls and systems for applications in aerospace, defense, industrial and medical devices. The company operates under four segmen ...
in
Westcott, Buckinghamshire Westcott is a village and civil parishes in England, civil parish in the unitary authority area of Buckinghamshire, England, about west of Waddesdon. The Toponymy, toponym is derived from the Old English for "west cottage". The Church of Engla ...
, England. It uses approx. of
hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly hazardous unless handled in solution as, for example, hydraz ...
and
nitrogen tetroxide Dinitrogen tetroxide, commonly referred to as nitrogen tetroxide (NTO), and occasionally (usually among ex-USSR/Russian rocket engineers) as amyl, is the chemical compound N2O4. It is a useful reagent in chemical synthesis. It forms an equilibrium ...
for propulsion, including available for the Jupiter Orbit Insertion plus subsequent orbital maneuvers. The engine provides a thrust of 645
newton Newton most commonly refers to: * Isaac Newton (1642–1726/1727), English scientist * Newton (unit), SI unit of force named after Isaac Newton Newton may also refer to: People * Newton (surname), including a list of people with the surname * ...
s. The engine bell is enclosed in a debris shield fixed to the spacecraft body, and is used for major burns. For control of the vehicle's orientation (
attitude control Spacecraft attitude control is the process of controlling the orientation of a spacecraft (vehicle or satellite) with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, ...
) and to perform trajectory correction maneuvers, ''Juno'' utilizes a
monopropellant Monopropellants are propellants consisting of chemicals that release energy through exothermic chemical decomposition. The molecular bond energy of the monopropellant is released usually through use of a catalyst. This can be contrasted with biprop ...
reaction control system A reaction control system (RCS) is a spacecraft system that uses Thrusters (spacecraft), thrusters to provide Spacecraft attitude control, attitude control and translation (physics), translation. Alternatively, reaction wheels can be used for at ...
(RCS) consisting of twelve small thrusters that are mounted on four engine modules.


Galileo plaque and minifigures

''Juno'' carries a plaque to Jupiter, dedicated to
Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 â€“ 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...
. The plaque was provided by the
Italian Space Agency The Italian Space Agency (; ASI) is a government agency established in 1988 to fund, regulate and coordinate space exploration activities in Italy. The agency cooperates with numerous national and international entities who are active in aerospac ...
(ASI) and measures . It is made of flight-grade
aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
and weighs . The plaque depicts a portrait of Galileo and a text in Galileo's own handwriting, penned in January 1610, while observing what would later be known to be the
Galilean moons The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter. They are, in descending-size order, Ganymede (moon), Ganymede, Callisto (moon), Callisto, Io (moon), Io, and Europa (moon), Europa. They are the most apparent m ...
. The text translates as: The spacecraft also carries three
Lego minifigure A Lego minifigure, often simply referred to as a Lego figure or a minifig, is a small plastic Joint, articulated figurine made of special Lego bricks produced by Denmark, Danish building toy manufacturer The Lego Group. They were first produced ...
s representing Galileo Galilei, the Roman god
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, and his sister and wife, the goddess
Juno Juno commonly refers to: *Juno (mythology), the Roman goddess of marriage and queen of the gods * ''Juno'' (film), the 2007 film Juno may also refer to: Arts, entertainment and media Fictional characters *Juno, a character in the book ''Juno of ...
. In Roman mythology, Jupiter drew a veil of clouds around himself to hide his mischief. Juno was able to peer through the clouds and reveal Jupiter's true nature. The Juno minifigure holds a magnifying glass as a sign of searching for the truth, and Jupiter holds a lightning bolt. The third Lego crew member, Galileo Galilei, has his telescope with him on the journey. The figurines were produced in partnership between NASA and
Lego Lego (, ; ; stylised as LEGO) is a line of plastic construction toys manufactured by the Lego Group, a privately held company based in Billund, Denmark. Lego consists of variously coloured interlocking plastic bricks made of acrylonitri ...
as part of an outreach program to inspire children's interest in
science, technology, engineering, and mathematics Science, technology, engineering, and mathematics (STEM) is an umbrella term used to group together the distinct but related technical disciplines of science, technology, engineering, and mathematics. The term is typically used in the context of ...
(STEM). Although most Lego toys are made of plastic, Lego specially made these minifigures of aluminum to endure the extreme conditions of space flight.


Scientific results

Among early results, ''Juno'' gathered information about Jovian lightning that revised earlier theories. ''Juno'' provided the first views of Jupiter's north pole, as well as providing insight about Jupiter's aurorae, magnetic field, and atmosphere. In 2021, analysis of the frequency of interplanetary dust impacts (primarily on the backs of the solar panels), as Juno passed between Earth and the asteroid belt, indicated that this dust, which causes the
Zodiacal light The zodiacal light (also called false dawn when seen before sunrise) is a faint glow of diffuse sunlight scattered by interplanetary dust. Brighter around the Sun, it appears in a particularly dark night sky to extend from the Sun's direct ...
, comes from
Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...
, rather than from comets or asteroids that come from the outer solar system, as was previously thought. Juno made many discoveries that are challenging existing theories about Jupiter's formation. When Juno flew over the poles of Jupiter it imaged clusters of stable cyclones that exist at the poles. It found that the magnetosphere of Jupiter is uneven and chaotic. Using its Microwave Radiometer, Juno found that the red and white bands that can be seen on Jupiter extend hundreds of kilometers into the Jovian atmosphere, yet the interior of Jupiter is not evenly mixed. This has resulted in the theory that Jupiter does not have a solid core as previously thought, but a "fuzzy" core made of pieces of rock and
metallic hydrogen Metallic hydrogen is a phase of hydrogen in which it behaves like an electrical conductor. This phase was predicted in 1935 on theoretical grounds by Eugene Wigner and Hillard Bell Huntington. At high pressure and temperatures, metallic hydr ...
. This peculiar core may be a result of a collision that happened early on in Jupiter's formation. In April 2020, ''Juno'' detected a meteor impact on Jupiter, with estimated mass of 250-5000 kg. Results from ''Juno'' on storms suggests that they are far taller than expected, with some extending 60 miles (100 kilometers) below the cloud tops and others, including the Great Red Spot, extending over 200 miles (350 kilometers). With ''Juno'' traveling low over Jupiter's cloud deck at about 130,000 mph (209,000 kph) Juno scientists were able to measure velocity changes as small 0.01 millimeter per second using a NASA's Deep Space Network tracking antenna, from a distance of more than 400 million miles (650 million kilometers). This enabled the team to constrain the depth of the Great Red Spot to about 300 miles (500 kilometers) below the cloud tops. The new results show that the cyclones are warmer on top, with lower atmospheric densities, while they are colder at the bottom, with higher densities. Anticyclones, which rotate in the opposite direction, are colder at the top but warmer at the bottom.


Timeline


Gallery


Jupiter

File:Jupiter- NASA JUNO Processed Image.jpg, Perijove 26 image File:PIA21032 Jupiter Down Under.jpg, Image from about of Jupiter's southern polar region (27 August 2016) File:PIA21034 Arrival and Departure at Jupiter.jpg, Jupiter growing and shrinking in apparent size before and after the spacecraft made its closest approach (27 August 2016) File:PIA21033 Juno's View of Jupiter's Southern Lights.jpg, Infrared view of the southern aurora of Jupiter (27 August 2016) File:PIA21641-Jupiter-SouthernStorms-JunoCam-20170525.jpg, Southern storms of Jupiter File:When Jovian Light and Dark Collide.png, Area of Jupiter where multiple atmospheric conditions appear to collide (27 March 2017) File:Jupiter’s Clouds of Many Colors.png, Retreating from Jupiter, about above the cloud tops (19 May 2017) File:Jupiter A New Point of View.png, Image taken from above the atmosphere at a latitude of −36.9° (10 July 2017) File:Great red spot juno 20170712.jpg, Closeup of the
Great Red Spot The Great Red Spot is a persistent high-pressure area, high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. It is the most recognizable feature on Jupiter, owing to its red-o ...
taken from about above it (11 July 2017) File:Jupiters iconic Great Red Spot.jpg, The
Great Red Spot The Great Red Spot is a persistent high-pressure area, high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. It is the most recognizable feature on Jupiter, owing to its red-o ...
as seen by
JunoCam JunoCam (or JCM) is the visible-light camera/telescope onboard NASA, NASA's Juno (spacecraft), ''Juno'' spacecraft that entered orbit around Jupiter in 2016. The camera is operated by the JunoCam Digital Electronics Assembly (JDEA). Both the camer ...
in April 2018 File:PIA22946-Jupiter-RedSpot-JunoSpacecraft-20190212.jpg,
Jupiter viewed by Juno
(12 February 2019)
File:PIA23807-PlanetJupiter-FlyOver-Animation-20200602.webm,
Jupiter flyover
(Juno; 05:07; 2 June 2020)
File:PIA22690 - Jupiter in the Rearview Mirror (panorama).jpg, Photograph taken at the end of Perijove 15 (September 6, 2018)


Moons

File:Ganymede_-_Perijove_34_Composite.png, Ganymede, taken by the JunoCam instrument during ''Juno''s flyby on 7 June 2021 File:Ganymede infrared NASA Juno JIRAM.jpg, Infrared view of Ganymede during the anniversary flyby by Juno File:Europa in natural color.png, View of Europa taken during Junos flyby on 29 September 2022 File:Io by JunoCam, processed by Roman Tkachenko.png, Low resolution view of Io captured by JunoCam (September 2017) File:Io seen by JunoCam.png, Io, as recorded by JunoCam
(2 September 2017) File:189401-JupiterMoon-Io-PlumeNearTerminator-Juno-20181221.jpg, Plume near Io's terminator
(21 December 2018) File:PIA26234-JupiterMoonIo-Volcanos-20231015.jpg, Io, viewed by JunoCam
Several Volcanos
(15 October 2023) File:PIA26235-JupiterMoonIo-Plume-20231015.jpg, Io, viewed by JunoCam
Volcanic plume
(15 October 2023) File:Io_imaged_by_Juno_spacecraft.png, Io, taken by the JunoCam instrument during ''Juno''s flyby
(30 December 2023)


See also

*
Atmosphere of Jupiter 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, a ...
*
Comet Shoemaker–Levy 9 Comet Shoemaker–Levy 9 ( formally designated D/1993 F2) was a comet that broke apart in July 1992 and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects. ...
* ''
Europa Clipper Europa Clipper (previously known as Europa Multiple Flyby Mission) is a space probe developed by NASA to study Europa (moon), Europa, a Galilean moon of Jupiter. It was launched on October 14, 2024. The spacecraft used a gravity assist from Mar ...
'' *
Exploration of Jupiter The exploration of Jupiter has been conducted via close observations by robotic spacecraft, automated spacecraft. It began with the arrival of ''Pioneer 10'' into the Moons of Jupiter, Jovian system in 1973, and, , has continued with eight furth ...
*
Jupiter Icy Moons Explorer The Jupiter Icy Moons Explorer (Juice, formerly JUICE) is an interplanetary spacecraft on its way to orbit and study three icy moons of Jupiter (planet), Jupiter: Ganymede (moon), Ganymede, Callisto (moon), Callisto, and Europa (moon), Europa ...
*
List of missions to the outer planets A total of nine spacecraft have been launched on missions that involve visits to the outer planets; all nine missions involve encounters with Jupiter, with four spacecraft also visiting Saturn. One spacecraft, ''Voyager 2'', also visited Uranu ...
*
Moons of Jupiter There are 97 Natural satellite, moons of Jupiter with confirmed orbits . This number does not include a number of meter-sized moonlets thought to be shed from the inner moons, nor hundreds of possible kilometer-sized outer irregular moons that ...


References


External links

*
''Juno'' mission
at
Southwest Research Institute Southwest Research Institute (SwRI), headquartered in San Antonio, Texas, is an independent and nonprofit applied research and development (R&D) organization. Founded in 1947 by oil businessman Tom Slick, it provides contract research and deve ...

''Juno'' Mission
a
NASA's Solar System Exploration
* ,
Bill Nye William Sanford Nye (; born November 27, 1955) is an American science communicator, television presenter, and former mechanical engineer. He is best known as the host of the science education television show '' Bill Nye the Science Guy'' (1 ...
discussing the science behind NASA's ''Juno'' mission to Jupiter
JunoCam image processing
web site
Animation of perijove 15 flyby
by Gerald Eichstädt (se
channel
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Animation of perijove 16 flyby
by Gerald Eichstädt and Seán Doran (see album
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Juno image album
by Kevin M. Gill {{Portal bar, Astronomy, Stars, Spaceflight, Science NASA space probes New Frontiers program Lockheed Martin satellites and probes Missions to Jupiter Orbiters (space probe) Space probes launched in 2011 2011 in the United States Spacecraft launched by Atlas rockets Articles containing video clips