Juno (spacecraft)

Last updated
Juno Transparent.png
Artist's rendering of the Juno spacecraft
Mission type Jupiter orbiter
Operator NASA  / JPL
COSPAR ID 2011-040A
SATCAT no. 37773
Mission durationPlanned: 7 years
Elapsed: 7 years, 7 months, 24 days

Cruise: 4 years, 10 months, 29 days
Science phase: 4 years (extended until July 2021)
Spacecraft properties
Manufacturer Lockheed Martin
Launch mass3,625 kg (7,992 lb) [1]
Dry mass1,593 kg (3,512 lb) [2]
Dimensions20.1 × 4.6 m (66 × 15 ft) [2]
Power14 kW at Earth, [2] 435 W at Jupiter [1]
2 × 55-ampere-hour lithium-ion batteries [2]
Start of mission
Launch dateAugust 5, 2011, 16:25 (2011-08-05UTC16:25)  UTC
Rocket Atlas V 551 (AV-029)
Launch site Cape Canaveral SLC-41
Contractor United Launch Alliance
Flyby of Earth
Closest approachOctober 9, 2013
Distance559 km (347 mi)
Jupiter orbiter
Orbital insertionJuly 5, 2016, 03:53 UTC [3]
2 years, 8 months, 24 days ago
Orbits37 (planned) [4] [5]
Orbit parameters
Perijove4,200 km (2,600 mi) altitude
75,600 km (47,000 mi) radius
Apojove8.1 million km (5.0 million mi)
Inclination90 degrees (polar orbit)
Juno mission insignia.svg
Juno mission insignia  

Juno is a NASA space probe orbiting the planet Jupiter. It was built by Lockheed Martin and is operated by NASA 's Jet Propulsion Laboratory. The spacecraft was launched from Cape Canaveral Air Force Station on August 5, 2011 (UTC), as part of the New Frontiers program, [6] and entered a polar orbit of Jupiter on July 5, 2016 (UTC; July 4 U.S. time), [4] [7] to begin a scientific investigation of the planet. [8] After completing its mission, Juno will be intentionally deorbited into Jupiter's atmosphere. [8]

NASA space-related agency of the United States government

The National Aeronautics and Space Administration is an independent agency of the United States Federal Government responsible for the civilian space program, as well as aeronautics and aerospace research.

Space probe unmanned robotic spacecraft that does not orbit the Earth, but, instead, explores further into outer space

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

Jupiter Fifth planet from the Sun in the Solar System

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined. Jupiter and Saturn are gas giants; the other two giant planets, Uranus and Neptune, are ice giants. Jupiter has been known to astronomers since antiquity. It is named after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest natural object in the night sky after the Moon and Venus.


Juno's mission is to measure Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. It will also search 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, and its deep winds, which can reach speeds up to 618 kilometers per hour (384 mph). [9]

Magnetic field spatial distribution of vectors allowing the calculation of the magnetic force on a test particle

A magnetic field is a vector field that describes the magnetic influence of electric charges in relative motion and magnetized materials. Magnetic fields are observed in a wide range of size scales, from subatomic particles to galaxies. In everyday life, the effects of magnetic fields are often seen in permanent magnets, which pull on magnetic materials and attract or repel other magnets. Magnetic fields surround and are created by magnetized material and by moving electric charges such as those used in electromagnets. Magnetic fields exert forces on nearby moving electrical charges and torques on nearby magnets. In addition, a magnetic field that varies with location exerts a force on magnetic materials. Both the strength and direction of a magnetic field vary with location. As such, it is an example of a vector field.

Magnetosphere of Jupiter magnetosphere of the planet Jupiter

The magnetosphere of Jupiter is the cavity created in the solar wind by the planet's magnetic field. Extending up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction, Jupiter's magnetosphere is the largest and most powerful of any planetary magnetosphere in the Solar System, and by volume the largest known continuous structure in the Solar System after the heliosphere. Wider and flatter than the Earth's magnetosphere, Jupiter's is stronger by an order of magnitude, while its magnetic moment is roughly 18,000 times larger. The existence of Jupiter's magnetic field was first inferred from observations of radio emissions at the end of the 1950s and was directly observed by the Pioneer 10 spacecraft in 1973.

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.

Juno is the second spacecraft to orbit Jupiter, after the nuclear powered Galileo orbiter, which orbited from 1995 to 2003. [8] Unlike all earlier spacecraft sent to the outer planets, [8] Juno is powered by solar arrays, commonly used by satellites orbiting Earth and working in the inner Solar System, whereas radioisotope thermoelectric generators are commonly used for missions to the outer Solar System and beyond. For Juno, however, the three largest solar array wings ever deployed on a planetary probe play an integral role in stabilizing the spacecraft as well as generating power. [10]

Nuclear power power generated from sustained nuclear fission

Nuclear power is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant. As a nuclear technology, nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by nuclear fission of uranium and plutonium. Nuclear decay processes are used in niche applications such as radioisotope thermoelectric generators. Generating electricity from fusion power remains at the focus of international research. This article mostly deals with nuclear fission power for electricity generation.

<i>Galileo</i> (spacecraft) Unmanned NASA spacecraft which studied the planet Jupiter and its moons

Galileo was an American unmanned spacecraft that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989 by Space ShuttleAtlantis. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit Jupiter. It launched the first probe into Jupiter, directly measuring its atmosphere. Despite suffering major antenna problems, Galileo achieved the first asteroid flyby, of 951 Gaspra, and discovered the first asteroid moon, Dactyl, around 243 Ida. In 1994, Galileo observed Comet Shoemaker–Levy 9's collision with Jupiter.

Solar panel Absorb sunlight as a source of energy to generate electricity

Photovoltaic solar panels absorb sunlight as a source of energy to generate electricity. A photovoltaic (PV) module is a packaged, connected assembly of typically 6x10 photovoltaic solar cells. Photovoltaic modules constitute the photovoltaic array of a photovoltaic system that generates and supplies solar electricity in commercial and residential applications.


Juno's name comes from Greek and Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife, the goddess Juno, was able to peer through the clouds and reveal Jupiter's true nature.

Classical mythology both the body of and the study of myths from the ancient Greeks and Romans as they are used or transformed by cultural reception

Classical Greco-Roman mythology, Greek and Roman mythology or Greco-Roman mythology is both the body of and the study of myths from the ancient Greeks and Romans as they are used or transformed by cultural reception. Along with philosophy and political thought, mythology represents one of the major survivals of classical antiquity throughout later Western culture. The Greek word mythos refers to the spoken word or speech, but it also denotes a tale, story or narrative.

Jupiter (mythology) King of the gods in ancient Roman religion and myth

Jupiter, also known as Jove, was the god of the sky and thunder and king of the gods in Ancient Roman religion and mythology. Jupiter was the chief deity of Roman state religion throughout the Republican and Imperial eras, until Christianity became the dominant religion of the Empire. In Roman mythology, he negotiates with Numa Pompilius, the second king of Rome, to establish principles of Roman religion such as offering, or sacrifice.

Juno (mythology) Ancient Roman goddess of marriage and childbirth

Juno was an ancient Roman goddess, the protector and special counselor of the state. A daughter of Saturn, she is the wife of Jupiter and the mother of Mars, Vulcan, Bellona and Juventas. She is the Roman equivalent of Hera, queen of the gods in Greek mythology; like Hera, her sacred animal was the peacock. Her Etruscan counterpart was Uni, and she was said to also watch over the women of Rome. As the patron goddess of Rome and the Roman Empire, Juno was called Regina ("Queen") and was a member of the Capitoline Triad, centered on the Capitoline Hill in Rome; it consisted of her, Jupiter, and Minerva, goddess of wisdom.

NASA [11]

The mission had previously been referred to by the backronym Jupiter Near-polar Orbiter. [12] Juno is sometimes called New Frontiers 2 as the second mission in the New Frontiers program, [13] [14] but is not to be confused with New Horizons 2, a proposed but unselected New Frontiers mission.

A backronym, or bacronym, is a constructed phrase that purports to be the source of a word that is an acronym. Backronyms may be invented with either serious or humorous intent, or they may be a type of false etymology or folk etymology.

<i>New Horizons 2</i>

New Horizons 2 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 development at the time. In March 2005, the proposal was not selected for further development because of a shortage of plutonium-238 needed for the radioisotope thermoelectric generator (RTG). The New Horizons 2 study was funded out of the New Frontiers program, and was delivered to the U.S. Congress in June 2005.


Juno's interplanetary trajectory en.svg
Juno's interplanetary trajectory; tick marks at 30-day intervals.
Juno spacecraft trajectory animation
Animation of Juno's trajectory from August 5, 2011, to July 30, 2021
Juno *   Earth  *   Mars  *   Jupiter Animation of Juno trajectory.gif
Animation of Juno's trajectory from August 5, 2011, to July 30, 2021
  Juno ·   Earth  ·   Mars  ·   Jupiter

Juno was selected on June 9, 2005, as the next New Frontiers mission after New Horizons . [15] The desire for a Jupiter probe was strong in the years prior to this, but there had not been any approved missions. [16] [17] The Discovery Program had passed over the somewhat similar but more limited Interior Structure and Internal Dynamical Evolution of Jupiter (INSIDE Jupiter) proposal, [17] and the turn-of-the-century era Europa Orbiter was canceled in 2002. [16] The flagship-level Europa Jupiter System Mission was in the works in the early 2000s, but funding issues resulted in it evolving into ESA's Jupiter Icy Moons Explorer. [18]

Discovery Program NASAs space exploration missions

NASA's Discovery Program is a series of lower-cost, highly focused American scientific space missions that are exploring the Solar System. It was founded in 1992 to implement then-NASA Administrator Daniel S. Goldin's vision of "faster, better, cheaper" planetary missions. Discovery missions differ from traditional NASA missions where targets and objectives are pre-specified. Instead, these cost-capped missions are proposed and led by a scientist called the Principal Investigator (PI). Proposing teams may include people from industry, small businesses, government laboratories, and universities. Proposals are selected through a competitive peer review process. All of the completed Discovery missions are accomplishing ground-breaking science and adding significantly to the body of knowledge about the Solar System.

Europa Orbiter cancelled space probe

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 missions. Europa Orbiter received pre-project funding in 1998, and resulted from NASA's Fire and Ice project.

Europa Jupiter System Mission – Laplace proposed joint NASA/ESA unmanned space mission

The Europa Jupiter System Mission – Laplace (EJSM/Laplace) was a proposed joint NASA/ESA unmanned space mission slated to launch around 2020 for the in-depth exploration of Jupiter's moons with a focus on Europa, Ganymede and Jupiter's magnetosphere. The mission would have comprised at least two independent elements, NASA's Jupiter Europa Orbiter (JEO) and ESA's Jupiter Ganymede Orbiter (JGO), to perform coordinated studies of the Jovian system.

Juno completed a five-year cruise to Jupiter, arriving on July 5, 2016. [7] The spacecraft traveled a total distance of roughly 2.8 billion kilometers (18.7 astronomical units; 1.74 billion miles) to reach Jupiter. [19] The spacecraft was designed to orbit Jupiter 37 times over the course of its mission. This was originally planned to take 20 months. [4] [5] Juno's trajectory used a gravity assist speed boost from Earth, accomplished by an Earth flyby in October 2013, two years after its launch on August 5, 2011. [20] 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 called the Science Orbit. Because of a suspected problem in Juno's main engine, the burn of December 11 was canceled, and Juno will remain in its 53-day orbit for its remaining orbits of Jupiter. [21]

During the science mission, infrared and microwave instruments will measure the thermal radiation emanating from deep within Jupiter's atmosphere. 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 that drives natural circulation patterns in Jupiter's atmosphere. Other instruments aboard Juno will gather data about its gravitational field and polar magnetosphere. The Juno mission was planned to conclude in February 2018, after completing 37 orbits of Jupiter. The probe was then intended to be de-orbited and burn up in Jupiter's outer atmosphere, [4] [5] to avoid any possibility of impact and biological contamination of one of its moons. [22]

Flight trajectory


Juno was launched atop the Atlas V at Cape Canaveral Air Force Station, Florida. The Atlas V (AV-029) used a Russian-built RD-180 main engine, powered by kerosene and liquid oxygen. At ignition it underwent checkout 3.8 seconds prior to the ignition of five strap-on solid rocket boosters (SRBs). 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 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. [23] 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 escape trajectory in a heliocentric orbit.

Prior to separation, the Centaur stage used onboard reaction engines 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 panels. [23] Following the full deployment and locking of the solar panels, Juno's batteries began to recharge. Deployment of the solar panels reduced Juno's 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. [22] [24]

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. [25] [26] When it reached the Jovian system, Juno had traveled approximately 19 AU, almost two billion miles. [27]

Flyby of the Earth

South America [28] as seen by JunoCam on its October 2013 Earth flyby
Video of Earth and Moon taken by the Juno spacecraft

After traveling for about a year in an elliptical heliocentric orbit, Juno fired its engine twice in 2012 near aphelion (beyond the orbit of Mars) to change its orbit and return to pass by the Earth in October 2013. [25] It used Earth's gravity to help slingshot itself toward the Jovian system in a maneuver called a gravity assist. [29] The spacecraft received a boost in speed of more than 3.9 km/s (8,800 mph), and it was set on a course to Jupiter. [29] [30] [31] 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. [29] [32]

Insertion into jovian orbit

Jupiter's gravity accelerated the approaching spacecraft to around 210,000 km/h (130,000 mph). [33] On July 5, 2016, between 03:18 and 03:53  UTC Earth-received time, an insertion burn lasting 2,102 seconds decelerated Juno by 542 m/s (1,780 ft/s) [34] and changed its trajectory from a hyperbolic flyby to an elliptical, polar orbit with a period of about 53.5 days. [35] The spacecraft successfully entered Jupiter orbit on July 5 at 03:53 UTC. [3]

Orbit and environment

Juno's elliptical orbit and the Jovian radiation belts Juno trajectory through radiation belts.png
Juno's elliptical orbit and the Jovian radiation belts

Juno's highly elliptical initial polar orbit takes it within 4,200 kilometers (2,600 mi) of the planet and out to 8.1 million km (5.0 million mi), far beyond Callisto's orbit. An eccentricity-reducing burn, called the Period Reduction Maneuver, was planned that would drop the probe into a much shorter 14 day science orbit. [36] 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. [21] Juno will now complete only 12 science orbits before the end of its budgeted mission plan, ending July 2018. [37]

The orbits were carefully planned in order to minimize contact with Jupiter's dense radiation belts, 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. [8] [38] The "Juno Radiation Vault", with 1-centimeter-thick titanium walls, also aids in protecting Juno's electronics. [39] Despite the intense radiation, JunoCam and the Jovian Infrared Auroral Mapper (JIRAM) are expected to endure at least eight orbits, while the Microwave Radiometer (MWR) should endure at least eleven orbits. [40] Juno will receive much lower levels of radiation in its polar orbit than the Galileo orbiter received in its equatorial orbit. Galileo's subsystems were damaged by radiation during its mission, including an LED in its data recording system. [41]

Orbital operations

Animation of Juno's trajectory around Jupiter from June 1, 2016, to July 31, 2021
Juno *   Jupiter Animation of Juno trajectory around Jupiter.gif
Animation of Juno's trajectory around Jupiter from June 1, 2016, to July 31, 2021
  Juno ·   Jupiter

The spacecraft completed its first flyby of Jupiter (perijove 1) on August 27, 2016, and captured the first images of the planet's north pole. [42]

On October 14, 2016, days prior to perijove 2 and the planned Period Reduction Maneuver, telemetry showed that some of Juno's helium valves were not opening properly. [43] On October 18, 2016, some 13 hours before its second close approach to Jupiter, Juno entered into safe mode, 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. [44]

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. [45] Perijove 4 occurred on February 2, with all instruments operating. [21] Perijove 5 occurred on March 27, 2017. [46] Perijove 6 took place on May 19, 2017. [46] [47]

Although the mission's lifetime is inherently limited by radiation exposure, almost all of this dose was planned to be acquired during the perijoves. As of 2017, 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 to determine if it will receive funding for an extended mission. [21]

In June 2018, NASA extended the mission operations plan to July 2021. [48] When Juno reaches the end of the mission, it will perform a controlled deorbit and disintegrate into Jupiter's atmosphere. During the mission, the spacecraft will be exposed to high levels of radiation from Jupiter's magnetosphere, which may cause future failure of certain instruments and risk collision with Jupiter's moons. [49] [50]

Planned deorbit and disintegration

NASA plans to deorbit the spacecraft into the atmosphere of Jupiter on July 30, 2021. [51] The controlled deorbit is intended to eliminate space debris and risks of contamination in accordance with NASA's Planetary Protection Guidelines. [50] [49] [52]


Scott Bolton of the Southwest Research Institute in San Antonio, Texas is the principal investigator and is responsible for all aspects of the mission. The Jet Propulsion Laboratory in California manages the mission and the Lockheed Martin Corporation 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, Andrew Ingersoll of California Institute of Technology, Frances Bagenal of the University of Colorado at Boulder, and Candy Hansen of the Planetary Science Institute. Jack Connerney of the Goddard Space Flight Center served as instrument lead. [53] [54]


Juno was originally proposed at a cost of approximately US$700 million (fiscal year 2003) for a launch in June 2009. NASA budgetary restrictions resulted in postponement until August 2011, and a launch on board an Atlas V rocket in the 551 configuration. As of June 2011, the mission was projected to cost US$1.1 billion over its life. [55] [ needs update ]

Scientific objectives

Jupiter imaged using the VISIR instrument on the VLT. These observations will inform the work to be undertaken by Juno. Jupiter imaged using the VISIR instrument on the VLT.jpg
Jupiter imaged using the VISIR instrument on the VLT. These observations will inform the work to be undertaken by Juno.

The Juno spacecraft's suite of science instruments will: [57]

Among early results, Juno gathered information about Jovian lightning that revised earlier theories. [61]

Scientific instruments

The Juno mission's scientific objectives will be achieved with a payload of nine instruments on board the spacecraft: [62] [63] [64] [65] [66]

IllustrationInstrument nameAbbr.Description and scientific objective
MWR(juno).jpg Microwave radiometer MWRThe microwave radiometer comprises six antennas mounted on two of the sides of the body of the probe. They will perform measurements of electromagnetic waves on frequencies in the microwave range: 600  MHz, 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 200-bar (20 MPa; 2,900 psi) pressure or 500–600 km (310–370 mi) 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. [67] [68] The MWR is designed to function through orbit 11 of Jupiter. [69]
(Principal investigator: Mike Janssen, Jet Propulsion Laboratory)
JIRAM(juno).jpg Jovian Infrared Auroral Mapper JIRAMThe spectrometer mapper JIRAM, operating in the near infrared (between 2 and 5 μm), conducts surveys in the upper layers of the atmosphere to a depth of between 50 and 70 km (31 and 43 mi) where the pressure reaches 5 to 7 bar (73 to 102 psi). 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, water vapor, ammonia and phosphine. It was not required that this device meets the radiation resistance requirements. [70] [71] [72] The JIRAM instrument is expected to operate through the eighth orbit of Jupiter. [69]
(Principal investigator: Alberto Adriani, Italian National Institute for Astrophysics)
MAG(Juno).png Magnetometer MAGThe 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 measure the strength and direction of the magnetic field lines, and the Advanced Stellar Compass (ASC), which will monitor the orientation of the magnetometer sensors.
(Principal investigator: Jack Connerney, NASA's Goddard Space Flight Center)
GS(Juno).png Gravity Science GSThe 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 on radio broadcasts issued by Juno toward Earth in Ka band and X band, which are frequency ranges that can conduct the study with fewer disruptions related to the solar wind or Jupiter's ionosphere. [73] [74] [63]
(Principal investigator: John Anderson, Jet Propulsion Laboratory; Principal investigator (Juno's Ka-band Translator): Luciano Iess, Sapienza University of Rome)
JADE(juno).jpg Jovian Auroral Distributions Experiment JADEThe 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. [63] [75]
(Principal investigator: David McComas, Southwest Research Institute)
JEDI(juno).jpg Jovian Energetic Particle Detector Instrument JEDIThe 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 of Jupiter. JEDI has three identical sensors dedicated to the study of particular ions of hydrogen, helium, oxygen and sulfur. [63] [76]
(Principal investigator: Barry Mauk, Applied Physics Laboratory)
Wave(juno).jpg 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.
(Principal investigator: William Kurth, University of Iowa)
UVS(juno).jpg Ultraviolet Spectrograph

Ultraviolet imaging spectrometer
UVSUVS will record the wavelength, position and arrival time of detected ultraviolet photons during the time when the spectrograph slit views Jupiter during each turn of the spacecraft. Using a 1024 × 256 micro channel plate detector, it will provide spectral images of the UV auroral emissions in the polar magnetosphere.
(Principal investigator: G. Randall Gladstone, Southwest Research Institute)
JunoCam(juno).jpg JunoCam JCMA 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. [77] It was anticipated that it would operate through only eight orbits of Jupiter due to the planet's damaging radiation and magnetic field, [69] but as of December 2018 (Perijove 17), JunoCam remains operational. [78]
(Principal investigator: Michael C. Malin, Malin Space Science Systems)
Where Juno's instruments are attached 2 (crop).jpg
Locations of Juno's science instruments
Juno Probe.stl
Interactive 3D model of Juno

Operational components

Solar panels

Illumination test on one of Juno's solar panels Illumination test on one of Juno's solar panels.jpg
Illumination test on one of Juno's solar panels

Juno is the first mission to Jupiter to use solar panels instead of the radioisotope thermoelectric generators (RTG) used by Pioneer 10 , Pioneer 11 , the Voyager program, Ulysses , Cassini–Huygens , New Horizons , and the Galileo orbiter. It is also the farthest solar-powered trip in the history of space exploration. [79] Once in orbit around Jupiter, Juno receives only 4% as much sunlight as it would on Earth, but the global shortage of plutonium-238, [80] [81] [82] [83] 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 AU from the Sun.

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. Each panel is 2.7 by 8.9 meters (8.9 by 29.2 ft) long, [84] the biggest on any NASA deep-space probe. [85]

The combined mass of the three panels is nearly 340 kg (750 lb). [86] If the panels were optimized to operate at Earth, they would produce 12 to 14 kilowatts of power. Only about 486 W was generated when Juno arrived at Jupiter, projected to decline to near 420 W as radiation degrades the cells. [87] 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-amp-hour lithium-ion batteries that are able to withstand the radiation environment of Jupiter provide power when Juno passes through eclipse. [88]


Juno's high-gain antenna dish being installed Juno's high-gain antenna just before installation.jpg
Juno's high-gain antenna dish being installed

Juno uses in-band signaling ("tones") for several critical operations as well as status reporting during cruise mode, [89] but it is expected to be used infrequently. Communications are via the 34-meter (112 ft) and 70-meter (230 ft) antennas of the NASA Deep Space Network (DSN) utilizing an X band direct link. [88] 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 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. [90] [ needs update ] 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 [91] 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.


Juno uses a LEROS 1b main engine with hypergolic propellant, manufactured by Moog Inc in Westcott, Buckinghamshire, England. [92] It uses hydrazine and nitrogen tetroxide for propulsion and provides a thrust of 645 newtons. 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) and to perform trajectory correction maneuvers, Juno utilizes a monopropellant reaction control system (RCS) consisting of twelve small thrusters that are mounted on four engine modules. [88]

Galileo plaque and minifigures

Galileo plaque Galileo plaque.jpg
Galileo plaque

Juno carries a plaque to Jupiter, dedicated to Galileo Galilei. The plaque was provided by the Italian Space Agency and measures 7.1 by 5.1 centimeters (2.8 by 2.0 in). It is made of flight-grade aluminum and weighs 6 grams (0.21 oz). [93] 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. [93] The text translates as:

On the 11th it was in this formation - and the star closest to Jupiter was half the size than the other and very close to the other so that during the previous nights all of the three observed stars looked of the same dimension and among them equally afar; so that it is evident that around Jupiter there are three moving stars invisible till this time to everyone.

The spacecraft also carries three Lego minifigures representing Galileo, the Roman god Jupiter, and his sister and wife, the goddess Juno. 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. [94] The figurines were produced in partnership between NASA and Lego as part of an outreach program to inspire children's interest in science, technology, engineering, and mathematics (STEM). [95] Although most Lego toys are made of plastic, Lego specially made these minifigures of aluminum to endure the extreme conditions of space flight. [96]


Date (UTC)Event
August 2011Launched
August 2012Trajectory corrections [97]
September 2012
October 2013Earth flyby for speed boost (from 126,000 to 150,000 km/h (78,000 to 93,000 mph)) [98] Gallery
July 5, 2016, 02:50Arrival at Jupiter and polar orbit insertion (1st orbit) [4] [5]
August 27, 2016, 12:50:44Perijove 1 [99] Gallery
October 19, 2016, 18:10:53Perijove 2: Planned Period Reduction Maneuver, but the main
engine's fuel pressurisation system did not operate as expected. [100]
December 11, 2016, 17:03:40Perijove 3 [101] [102]
February 2, 2017, 12:57:09Perijove 4 [102] [103]
March 27, 2017, 08:51:51Perijove 5 [46]
May 19, 2017, 06:00:47Perijove 6 [47]
July 11, 2017, 01:54:42Perijove 7: Fly-over of the Great Red Spot [104] [105]
September 1, 2017, 21:48:50Perijove 8 [106]
October 24, 2017, 17:42:31Perijove 9 [107]
December 16, 2017, 17:56:59Perijove 10 [108] [109]
February 7, 2018, 13:51:29Perijove 11
April 1, 2018, 09:45:42Perijove 12
May 24, 2018, 05:39:50Perijove 13
July 16, 2018, 05:17:22Perijove 14
September 7, 2018, 01:11:40Perijove 15
October 29, 2018, 21:06:00Perijove 16
December 21, 2018Perijove 17 [78]
February 12, 2019Perijove 18
April 6, 2019Perijove 19
May 29, 2019Perijove 20
July 21, 2019Perijove 21 [110]
September 12, 2019Perijove 22
November 3, 2019Perijove 23
December 26, 2019Perijove 24
February 17, 2020Perijove 25
April 10, 2020Perijove 26
June 2, 2020Perijove 27
July 25, 2020Perijove 28
September 16, 2020Perijove 29
November 8, 2020Perijove 30
December 30, 2020Perijove 31
February 21, 2021Perijove 32
April 15, 2021Perijove 33
June 7, 2021Perijove 34 [51]
July 30, 2021Perijove 35: End of mission [51] [111]
Perijove 6 pass of Jupiter (May 19, 2017) PIA21645-Jupiter-PerijovePass-JunoCam-20170525.jpg
Perijove 6 pass of Jupiter (May 19, 2017)

See also

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UVS (<i>Juno</i>)

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Microwave Radiometer (<i>Juno</i>)

Microwave Radiometer (MWR) is an instrument on the Juno orbiter sent to planet Jupiter. MWR is a multi-wavelength microwave radiometer for making observations of Jupiter's deep atmosphere. MWR can observe radiation from 1.37 to 50 cm in wavelength, from 600 MHz to 22 GHz in frequencies. This supports its goal of observing the previously unseen atmospheric features and chemical abundances hundreds of miles/km into Jupiter's atmosphere. MWR is designed to detect six different frequencies in that range using separate antennas.

Waves (<i>Juno</i>) experiment on the Juno spacecraft

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Europa Lander (NASA) proposed spacecraft concept by NASA for a lander for Jupiters moon Europa

Europa Lander is a proposed astrobiology mission concept by NASA to Europa, a moon of Jupiter. If selected and developed, it would be launched separately in 2025 to complement the studies by the Europa Clipper orbiter mission.


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