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Juno (spacecraft) facts for kids

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Juno
Juno Transparent.png
Artist's rendering of the Juno spacecraft
Names New Frontiers 2
Mission type Jupiter orbiter
Operator NASA / Jet Propulsion Laboratory
Website
  • (NASA)
  • (SwRI)
Mission duration Planned: 7 years
Elapsed: 13 years, 11 months, 25 days
Cruise: 4 years, 10 months, 29 days
Science phase: 4 years (in progress; extended until September 2025)
Spacecraft properties
Manufacturer Lockheed Martin Space
Launch mass 3,625 kg (7,992 lb)
Dry mass 1,593 kg (3,512 lb)
Dimensions 20.1 × 4.6 m (66 × 15 ft)
Power 14 kW at Earth, 435 W at Jupiter
2 × 55-ampere hour lithium-ion batteries
Start of mission
Launch date August 5, 2011, 16:25:00 UTC
Rocket Atlas V 551 (AV-029)
Launch site Cape Canaveral, SLC-41
Contractor United Launch Alliance
Flyby of Earth
Closest approach October 9, 2013
Distance 559 km (347 mi)
Jupiter orbiter
Orbital insertion July 5, 2016,
9 years, 25 days ago
Orbits 76 (planned)
Orbit parameters
Perijove 4,200 km (2,600 mi) altitude
75,600 km (47,000 mi) radius
Apojove 8.1×10^6 km (5.0×10^6 mi)
Inclination 90° (polar orbit)
Juno mission insignia.svg
Juno mission patch
New Frontiers
Juno lifted by overhead crane
Juno in launch configuration

The Juno spacecraft is a NASA space probe that orbits the giant planet Jupiter. It was built by Lockheed Martin and is operated by NASA's Jet Propulsion Laboratory. Juno launched from Cape Canaveral Air Force Station on August 5, 2011. It is part of the New Frontiers program, which sends probes to explore different parts of our Solar System.

Juno arrived at Jupiter and entered a special polar orbit on July 5, 2016. Its main job is to study Jupiter up close. Scientists want to learn about Jupiter's makeup, its gravity, its magnetic field, and the area around its poles called the polar magnetosphere. The mission also looks for clues about how Jupiter formed. This includes trying to find out if it has a rocky core, how much water is deep in its atmosphere, and how its strong winds move. These winds can blow at speeds of up to 620 kilometers per hour (about 385 miles per hour)!

Juno is the second spacecraft to orbit Jupiter. The first was the Galileo orbiter, which explored Jupiter from 1995 to 2003. Unlike many other spacecraft that travel far into the outer Solar System and use nuclear power, Juno uses solar panels. These are more common for satellites orbiting Earth or working closer to the Sun. Because Jupiter is so far from the Sun, Juno needed the largest solar panels ever used on a planetary probe when it launched. These huge panels help keep the spacecraft stable and provide all its power.

Why is it Called Juno?

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.

The name Juno comes from ancient Roman myths. In these stories, the god Jupiter would hide himself behind clouds. But his wife, the goddess Juno, could see through the clouds and discover his true self. This is like the spacecraft, which is designed to "see through" Jupiter's thick clouds to learn its secrets.

Sometimes, Juno is also called New Frontiers 2. This is because it's the second mission in NASA's New Frontiers program.

Mission Overview

Juno's interplanetary path.
Animation of Juno trajectory
Animation of Juno's journey from August 5, 2011.       Juno ·       Earth ·       Mars ·       Jupiter

Juno was chosen for the New Frontiers program on June 9, 2005. Before Juno, scientists really wanted to send a probe to Jupiter, but no missions had been approved for a while.

Juno took five years to travel to Jupiter, arriving on July 5, 2016. The spacecraft traveled about 2.8 billion kilometers (1.7 billion miles) to get there. It was designed to orbit Jupiter 37 times. This was originally planned to take about 20 months.

To get a speed boost, Juno used a gravity assist from Earth. This happened during an Earth flyby in October 2013, two years after its launch. When Juno reached Jupiter, it fired its engine to slow down and enter Jupiter's orbit.

The mission was originally set to end in February 2018. However, it has been extended multiple times. In January 2021, NASA extended the mission until September 2025. This allows Juno to study Jupiter's large moons: Ganymede, Europa, and Io. Juno flew very close to Ganymede on June 7, 2021, and Europa on September 29, 2022. It also had close flybys of Io on December 30, 2023, and February 3, 2024.

Journey to Jupiter

Atlas V Rocket Ready for Juno Mission
Juno ready for launch in 2011.

Launching into Space

Juno launched on an Atlas V rocket from Cape Canaveral Space Force Station in Florida. This happened on August 5, 2011, at 16:25 UTC. The rocket used a powerful main engine and five solid rocket boosters to lift off.

After the boosters fell away, a protective cover called the payload fairing separated. This cover kept Juno safe during its trip through Earth's atmosphere. Then, the Atlas V main engine shut off, and the Centaur second stage ignited. This stage fired twice, first putting Juno into a parking orbit around Earth, and then pushing it onto a path to escape Earth's gravity and head towards the Sun.

Before separating from the Centaur stage, Juno was spun up to 1.4 rotations per minute. This spin helps keep the spacecraft stable during its long journey. About 54 minutes after launch, Juno separated and began to unfold its large solar panels. Once the panels were fully open, Juno's batteries started recharging.

Earth Flyby and Speed Boost

South America seen by JunoCam during its October 2013 Earth flyby.

After traveling for about a year, Juno fired its engine twice to change its path. This brought it back to Earth for a close flyby on October 9, 2013. This maneuver, called a gravity assist, used Earth's gravity to give Juno a huge speed boost. It increased Juno's speed by more than 3.9 kilometers per second (about 8,700 miles per hour), sending it on its way to Jupiter. This flyby also allowed the Juno team to test some of the spacecraft's instruments.

Arriving at Jupiter

Jupiter's strong gravity pulled Juno in, speeding it up to about 210,000 kilometers per hour (130,000 miles per hour). On July 5, 2016, Juno fired its engine for over 2,100 seconds. This slowed it down enough to be captured by Jupiter's gravity. The spacecraft successfully entered an elliptical, polar orbit around Jupiter.

Orbiting Jupiter

Juno trajectory through radiation belts
Juno's elliptical orbit and Jupiter's radiation belts.

Juno's orbit is very stretched out. It comes as close as 4,200 kilometers (2,600 miles) to Jupiter's cloud tops and then swings out as far as 8.1 million kilometers (5 million miles). This special orbit helps Juno avoid Jupiter's intense radiation belts. These belts can damage spacecraft electronics and solar panels.

To protect its sensitive electronics, Juno has a special "Juno Radiation Vault." This vault has 1-centimeter-thick titanium walls, which reduce the radiation by 800 times. Even with this protection, the radiation is very strong.

How Juno Works

Animation of Juno trajectory around Jupiter
Animation of Juno's path around Jupiter from June 1, 2016, to October 25, 2025.       Juno ·       Jupiter
PIA24681-1041-Ganymede-JupiterMoon-Juno-20210607
Ganymede, photographed on June 7, 2021, by Juno during its extended mission.

Juno completed its first close flyby of Jupiter on August 26, 2016. It captured the first images of Jupiter's north pole.

On October 14, 2016, some of Juno's helium valves didn't open correctly. A few days later, Juno went into "safe mode." This means its computer detected a problem and powered down non-essential systems to protect itself. Because of this, no science data was collected during its second close approach. However, the mission team fixed the issue, and by December 11, 2016, most instruments were working again.

The mission was extended in June 2018 and again in January 2021. This allowed Juno to continue its studies until September 2025. During this extended phase, Juno has been making close flybys of Jupiter's largest moons: Ganymede, Europa, and Io. These flybys help scientists learn more about these fascinating worlds.

Planned End of Mission

NASA originally planned for Juno to intentionally crash into Jupiter's atmosphere after its mission. This is done to prevent any chance of the spacecraft accidentally hitting one of Jupiter's moons, especially Europa, which might have conditions suitable for life. This process helps avoid contaminating the moons with any tiny Earth microbes that might have survived on the spacecraft. However, with the mission extensions, the deorbit date has been pushed back.

The Juno Team

The Juno mission involves many talented people. Scott Bolton from the Southwest Research Institute is the main scientist in charge. The Jet Propulsion Laboratory in California manages the mission, and Lockheed Martin built the spacecraft. Many other scientists and institutions also help with the mission.

Mission Cost

The Juno mission was originally estimated to cost about $700 million in 2003. By 2019, the total cost for operations and data analysis through 2022 was projected to be $1.46 billion.

What Juno Studies

Jupiter imaged using the VISIR instrument on the VLT
Jupiter imaged using the VISIR instrument on the VLT. Juno builds on these observations.

Juno's science instruments are designed to answer big questions about Jupiter:

  • Water in Jupiter: It measures how much water is in Jupiter's atmosphere. This helps scientists understand how Jupiter and the rest of the Solar System formed.
  • Jupiter's Core: It tries to figure out the mass of Jupiter's core. This also helps with theories about the planet's formation.
  • Gravity and Mass: It precisely maps Jupiter's gravitational field. This shows how mass is spread out inside Jupiter, giving clues about its structure.
  • Magnetic Field: It maps Jupiter's magnetic field to understand where it comes from and how deep inside the planet it is created.
  • Atmosphere: It studies the different layers of Jupiter's atmosphere, including its temperature, clouds, and how its winds move.
  • Polar Lights: It explores the 3D structure of Jupiter's polar magnetosphere and its amazing auroras (like the Northern and Southern Lights on Earth).

Science Tools on Juno

Juno carries nine special instruments to achieve its goals:

Microwave Radiometer (MWR)

MWR(juno)
Microwave Radiometer

This instrument has six antennas that measure microwave energy. Microwaves can pass through Jupiter's thick atmosphere. The MWR measures water and ammonia deep in the atmosphere, up to 500-600 kilometers (310-370 miles) deep. This helps scientists understand how deep the atmospheric circulation goes.

Jovian Infrared Auroral Mapper (JIRAM)

JIRAM(juno)
Jovian Infrared Auroral Mapper

JIRAM is a camera that sees in near infrared light. It studies the upper layers of Jupiter's atmosphere. It also takes pictures of Jupiter's auroras. By measuring heat from the atmosphere, JIRAM can see how clouds with water move beneath the surface. It can also detect gases like methane and ammonia.

Magnetometer (MAG)

MAG(Juno)
MAG

The MAG instrument measures Jupiter's magnetic field. It helps map the field's strength and direction. This tells scientists about the inside of Jupiter and the structure of its polar magnetosphere.

Gravity Science (GS)

GS(Juno)
Gravity Science

This experiment measures Jupiter's gravity. Small changes in gravity affect Juno's speed as it orbits. By detecting these tiny speed changes using radio waves sent to Earth, scientists can create a map of how mass is distributed inside Jupiter.

Jovian Auroral Distributions Experiment (JADE)

JADE(juno)
JADE

JADE is a particle detector. It measures low-energy ions and electrons in Jupiter's auroras. This helps scientists understand the particles that create the stunning light shows at Jupiter's poles.

Jovian Energetic Particle Detector Instrument (JEDI)

JEDI(juno)
JEDI

JEDI also detects energetic particles, but at higher energies than JADE. It measures ions and electrons in Jupiter's polar magnetosphere. This helps scientists study how these particles behave in Jupiter's powerful magnetic environment.

Radio and Plasma Wave Sensor (Waves)

Wave(juno)
Radio and Plasma Wave Sensor

This instrument has two antennas that detect radio and plasma waves. It helps identify the regions where auroral currents flow and how particles are sped up to create Jupiter's radio emissions and auroras. It also observes how Jupiter's atmosphere and magnetosphere interact.

Ultraviolet Spectrograph (UVS)

UVS(juno)
Ultraviolet Spectrograph

UVS records ultraviolet light. It provides images of the UV light coming from Jupiter's auroras in the polar magnetosphere. This helps scientists understand the processes that cause these lights.

JunoCam (JCM)

JunoCam(juno)
JunoCam

JunoCam is a visible light camera. It was originally included for public outreach, but it's now also used to study Jupiter's clouds, especially those at the poles. Even though it was expected to last only about eight orbits due to radiation, JunoCam is still working well after more than 55 orbits!

Where Juno's science instruments are located.

Juno's Design

Solar Panels

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

Juno is the first mission to Jupiter to use solar panels instead of nuclear power. Even though Jupiter is far from the Sun, solar panel technology has improved a lot. Juno has three huge solar panels, each about 2.7 by 8.9 meters (9 by 29 feet). Together, they have 50 square meters (538 square feet) of solar cells. These were the largest solar panels ever on a NASA deep-space probe when Juno launched.

At Jupiter, Juno receives only about 4% of the sunlight it would get at Earth. The panels generate about 435 watts of power. Two large lithium-ion batteries store power for when Juno passes through Jupiter's shadow.

Communication

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

Juno communicates with Earth using large antennas from NASA's NASA Deep Space Network. It sends data back using X-band radio waves. The spacecraft's computer can send about 50 megabits of instrument data per second.

Because of communication limits, Juno can only send back about 40 megabytes of JunoCam images during each 11-day orbit. This means it sends between 10 and 100 images per orbit, depending on how much they are compressed. The main focus is on sending back scientific data from the other instruments.

Propulsion System

Juno uses a main engine for big maneuvers, like entering Jupiter's orbit. It also has twelve smaller thrusters. These small thrusters are used to control the spacecraft's direction and make small adjustments to its path.

Special Items on Juno

Galileo Plaque and Minifigures

Galileo plaque

Juno carries a special plaque dedicated to Galileo Galilei, a famous scientist. The plaque is made of aluminum and has a picture of Galileo. It also has text in Galileo's own handwriting from 1610. This text describes his observations of Jupiter's moons, which he was the first to see.

The spacecraft also carries three special Lego minifigures! These minifigures represent Galileo Galilei, the Roman god Jupiter, and the goddess Juno. The Juno minifigure holds a magnifying glass, showing her search for truth. Jupiter holds a lightning bolt. Galileo has his telescope. These special Lego figures are made of aluminum so they can survive the harsh conditions of space. They are part of a program to get kids interested in science, technology, engineering, and mathematics (STEM).

Discoveries and Results

Juno has already made many exciting discoveries about Jupiter. For example, it found new information about lightning on Jupiter, changing earlier ideas. It also gave us the first views of Jupiter's north pole and new insights into its auroras, magnetic field, and atmosphere.

In 2021, Juno helped scientists learn that the dust causing the Zodiacal light (a faint glow in the night sky) actually comes from Mars, not from comets or asteroids as previously thought.

Juno's findings are challenging existing ideas about how Jupiter formed. When it flew over Jupiter's poles, it saw stable clusters of cyclones. It also found that Jupiter's magnetosphere is uneven and chaotic. Using its Microwave Radiometer, Juno discovered that Jupiter's famous red and white bands extend hundreds of kilometers deep into the atmosphere. However, the inside of Jupiter is not evenly mixed. This has led to a new idea that Jupiter might not have a solid core. Instead, it might have a "fuzzy" core made of pieces of rock and metallic hydrogen. This unusual core might be the result of a collision that happened early in Jupiter's history.

In April 2020, Juno even detected a meteor impact on Jupiter!

Juno's studies of Jupiter's storms show they are much taller than expected. Some storms go 100 kilometers (60 miles) below the cloud tops. The famous Great Red Spot extends over 350 kilometers (200 miles) deep! By flying low over Jupiter's clouds, Juno could measure tiny changes in velocity. This helped scientists figure out that the Great Red Spot goes about 500 kilometers (300 miles) below the cloud tops. The new results also show that cyclones are warmer at the top and colder at the bottom, while anticyclones are colder at the top and warmer at the bottom.

Mission Timeline

Date (UTC) Event Latitude (centric) Longitude (Sys. III)
August 5, 2011, 16:25:00 Launched
August 5, 2012, 06:57:00 Deep Space Maneuvers (engine firings to change path)
September 3, 2012, 06:30:00
October 9, 2013, 19:21:00 Earth gravity assist (speed boost)
July 5, 2016, 03:53:00 Arrived at Jupiter and entered orbit. 30°
August 27, 2016, 12:50:44 Perijove 1 (first close pass by Jupiter) 100°
October 19, 2016, 18:10:53 Perijove 2: Planned engine burn did not happen due to a valve issue. 350°
December 11, 2016, 17:03:40 Perijove 3 10°
February 2, 2017, 12:57:09 Perijove 4 270°
March 27, 2017, 08:51:51 Perijove 5 180°
May 19, 2017, 06:00:47 Perijove 6 140°
July 11, 2017, 01:54:42 Perijove 7: Flew over the Great Red Spot. 50°
September 1, 2017, 21:48:50 Perijove 8 10° 320°
October 24, 2017, 17:42:31 Perijove 9 11° 230°
December 16, 2017, 17:56:59 Perijove 10 12° 300°
February 7, 2018, 13:51:49 Perijove 11 13° 210°
April 1, 2018, 09:45:57 Perijove 12 14° 110°
May 24, 2018, 05:40:07 Perijove 13 15° 20°
July 16, 2018, 05:17:38 Perijove 14 16° 70°
September 7, 2018, 01:11:55 Perijove 15 17° 340°
October 29, 2018, 21:06:15 Perijove 16 17° 250°
December 21, 2018, 17:00:25 Perijove 17 18° 160°
February 12, 2019, 16:19:48 Perijove 18 19° 240°
April 6, 2019, 12:13:58 Perijove 19 20° 100°
May 29, 2019, 08:08:13 Perijove 20 20° 10°
July 21, 2019, 04:02:44 Perijove 21 21° 280°
September 12, 2019, 03:40:47 Perijove 22 22° 320°
November 3, 2019, 23:32:56 Perijove 23 22° 190°
December 26, 2019, 16:58:59 Perijove 24: Distant Ganymede flyby. 23° 70°
February 17, 2020, 17:51:36 Perijove 25 23° 140°
April 10, 2020, 14:24:34 Perijove 26 24° 50°
June 2, 2020, 10:19:55 Perijove 27 25° 340°
July 25, 2020, 06:15:21 Perijove 28 25° 250°
September 16, 2020, 02:10:49 Perijove 29 26° 160°
November 8, 2020, 01:49:39 Perijove 30 27° 210°
December 30, 2020, 21:45:12 Perijove 31 27° 120°
February 21, 2021, 17:40:31 Perijove 32 28° 30°
April 15, 2021, 13:36:26 Perijove 33 29° 300°
June 8, 2021, 07:46:00 Perijove 34: Ganymede flyby (1,038 km from surface). Orbit period changed from 53 to 43 days. 28° 290°
July 21, 2021, 08:15:05 Perijove 35: End of first mission extension. 29° 300°
September 2, 2021 Perijove 36 30° 100°
October 16, 2021 Perijove 37 31° 40°
November 29, 2021 Perijove 38 31° 80°
January 12, 2022 Perijove 39 32° 90°
February 25, 2022 Perijove 40 33° 280°
April 9, 2022 Perijove 41 34° 60°
May 23, 2022 Perijove 42 35° 70°
July 5, 2022 Perijove 43 36° 310°
August 17, 2022 Perijove 44 37° 150°
September 29, 2022, 09:36 Perijove 45: Europa flyby (352 km from surface). Orbit period changed from 43 to 38 days. 37° 230°
November 6, 2022 Perijove 46 38° 350°
December 15, 2022 Perijove 47: Io flyby on Dec 14, 2022 (64,000 km from surface). 39° 160°
January 22, 2023 Perijove 48 40° 200°
March 1, 2023 Perijove 49 41° 170°
April 8, 2023 Perijove 50 42° 210°
May 16, 2023 Perijove 51 43° 140°
June 23, 2023 Perijove 52 44° 80°
July 31, 2023 Perijove 53: Io flyby on July 30, 2023 (22,000 km from surface). 45° 120°
September 7, 2023 Perijove 54 45° 190°
October 15, 2023 Perijove 55 46° 110°
November 22, 2023 Perijove 56 47° 120°
December 30, 2023 Perijove 57: Io flyby (1,500 km from surface). 47° 90°
February 3, 2024 Perijove 58: Io flyby (1,500 km from surface). Orbit period changed from 38 to 33 days. 48° 290°
March 7, 2024 Perijove 59: Distant Amalthea flyby (117,500 km). 49°
April 9, 2024 Perijove 60 50° 40°
May 12, 2024 Perijove 61 51° 250°
June 14, 2024 Perijove 62 52° 60°
July 17, 2024 Perijove 63 53° 260°
August 18, 2024 Perijove 64 54° 40°
September 20, 2024 Perijove 65 55° 240°
October 23, 2024 Perijove 66 56° 20°
November 25, 2024 Perijove 67 57° 120°
December 28, 2024 Perijove 68 57° 310°
January 30, 2025 Perijove 69 58° 110°
March 4, 2025 Perijove 70: Thebe flyby on March 2, 2025 (31,780 km). 59°
April 5, 2025 Perijove 71 60° 210°
May 8, 2025 Perijove 72 61° 50°
June 10, 2025 Perijove 73 62° 320°
July 13, 2025 Perijove 74 63° 180°
August 15, 2025 Perijove 75 63° 80°
September 17, 2025 Perijove 76: End of second mission extension. 64° 320°

Images for kids

Jupiter Views

Moon Views

See also

Kids robot.svg In Spanish: Juno (sonda espacial) para niños

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