Juno is a NASA space probe orbiting the planet Jupiter. Built by Lockheed Martin and 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. Juno entered a polar orbit 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. It will continue to explore Jupiter to study Jovian rings and inner moons area which is not well explored; this phase will also include close flybys of the moons Thebe, Amalthea, Adrastea, and Metis. Juno's mission is to measure Jupiter's composition, gravitational field, magnetic field, 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, and its deep winds, which can reach speeds up to 620 km/h (390 mph). Juno is the second spacecraft to orbit Jupiter, after the RTG-powered Galileo orbiter, which orbited from 1995 to 2003. Unlike all earlier spacecraft sent to the outer Solar System and beyond—which used radioisotope thermoelectric generators for power—Juno is powered by solar panels, more commonly used by satellites orbiting Earth and working in the inner Solar System. 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. As of August 6, 2026, Juno remained operational and in contact with Earth through the NASA Deep Space Network.
Naming 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. A NASA compilation of mission names and acronyms referred to the mission by the backronym 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 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, a proposed but unselected New Frontiers mission.
Overview
Juno was selected on June 1, 2005, as the next New Frontiers mission after New Horizons. 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 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 was canceled in 2002. 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. Juno completed a five-year cruise to Jupiter, arriving on July 5, 2016. The spacecraft traveled a total distance of roughly 2.8×10^9 km (19 AU; 1.7×10^9 mi) 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'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. 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 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 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, 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
… excerpt ends here. Continue reading the full article.
