Juno
Juno is a NASA space probe orbiting the planet Jupiter, built by Lockheed Martin and operated by NASA's Jet Propulsion Laboratory. Launched on August 5, 2011, from Cape Canaveral Air Force Station as part of the New Frontiers program, the spacecraft entered a polar orbit around Jupiter on July 5, 2016. Its mission is to study the planet's composition, gravitational and magnetic fields, and polar magnetosphere, while also investigating Jupiter's formation, including whether it has a rocky core, the amount of water in its deep atmosphere, mass distribution, and deep winds that can reach high speeds. Juno is the second spacecraft to orbit Jupiter, following the Galileo orbiter, and is unique among outer Solar System probes for being powered by solar panels rather than radioisotope thermoelectric generators. At launch, it carried the three largest solar panel wings ever deployed on a planetary probe, which also help stabilize the spacecraft. Originally planned for a 20-month mission of 37 orbits ending in February 2018, Juno has been approved to continue orbiting until contact is lost. Its extended mission includes close flybys of the inner moons Thebe, Amalthea, Adrastea, and Metis, as well as Ganymede, Europa, and Io, with the orbital period reduced to 33 days by February 2024. The spacecraft uses infrared and microwave instruments to measure thermal radiation from Jupiter's deep atmosphere, complementing earlier studies of composition and water abundance. As of August 6, 2026, Juno remained operational and in contact with Earth via the NASA Deep Space Network. The probe's name references the Roman goddess Juno, and it is sometimes called New Frontiers 2, though it is not an acronym.
- launch_date
- August 5, 2011 UTC
- operator
- NASA's Jet Propulsion Laboratory
- builder
- Lockheed Martin
- power_source
- Solar panels
- mission_type
- Orbiter
- target
- Jupiter
Lore & Background
Juno is a solar-powered NASA space probe, built by Lockheed Martin and operated by the Jet Propulsion Laboratory, that orbits Jupiter. Launched from Cape Canaveral Air Force Station in August 2011 as part of the New Frontiers program, it entered a polar orbit around Jupiter in July 2016. The spacecraft is the second to orbit the planet, following the RTG-powered Galileo orbiter. Unlike earlier outer Solar System probes, Juno is powered by three large solar panel wings—the largest ever deployed on a planetary probe at the time of launch—which also help stabilize the spacecraft. Its mission includes measuring Jupiter’s composition, gravitational and magnetic fields, and polar magnetosphere, as well as searching for evidence of a rocky core, the amount of deep-atmosphere water, mass distribution, and deep winds. Originally planned for a 20-month, 37-orbit science phase ending in a deorbit into Jupiter’s atmosphere, the mission was extended. The extended phase includes close flybys of the inner moons Thebe, Amalthea, Adrastea, and Metis, and study of the Jovian rings and inner moon region. The spacecraft completed a five-year cruise to Jupiter, using an Earth gravity assist in 2013. After a suspected main engine issue, it remained in a 53-day orbit until its first Ganymede encounter in June 2021. Subsequent flybys of Europa and Io reduced its orbital period to 33 days by February 2024. As of August 2026, Juno remained operational and in contact with Earth via the Deep Space Network.
Reader's Guide
Juno's significance lies in its investigation of Jupiter's deep atmosphere, gravitational and magnetic fields, and polar magnetosphere, providing clues about the planet's formation, including whether it has a rocky core and the amount of water present. Originally planned to be deorbited into Jupiter's atmosphere after 37 orbits, Juno has been approved to continue orbiting until contact is lost, exploring Jovian rings and inner moons such as Thebe, Amalthea, Adrastea, and Metis. As the first solar-powered spacecraft sent to the outer Solar System, it required the three largest solar panel wings ever deployed on a planetary probe at launch, which also stabilize the spacecraft.
Did You Know?
- Juno is named after the Roman goddess Juno, who could see through clouds to reveal Jupiter's true nature.
- Juno is the second spacecraft to orbit Jupiter, after the RTG-powered Galileo orbiter.
- Juno's solar panels are the three largest ever deployed on a planetary probe at the time of launching.
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