NASA JPL Juno
Lockheed Martin · Jupiter Polar Orbit Science Probe · USA · Digital Age (2010–present)
The Juno is an American Jovian orbiter — Lockheed Martin's NASA-funded New Frontiers Program mission to study its interior + magnetic field + atmosphere. Lockheed Martin developed Juno in 2003-2011 at the Denver / Waterton facility; launched on an Atlas V 551 from Cape Canaveral on 5 August 2011; arrived at the gas giant on 4 July 2016 after a 5-year cruise (including a 2013 Earth gravity-assist flyby). Juno has been in highly-elliptical polar orbit since 2016 + has executed ~70 close flybys of the planet through 2026.
Juno is a spin-stabilised solar-powered spacecraft — at 778 million km from the Sun, the craft is the most-distant solar-powered spacecraft ever flown. Dry mass 1,593 kg, launch mass 3,625 kg. Power: 3 × solar panels of 8.9 m² each (total 60 m²) generating ~14 kW at Earth + ~500 W in the Jovian system — sufficient for instruments + spacecraft systems. Instruments: gravity-science Doppler tracking, MAG magnetometer, MWR microwave radiometer, JIRAM infrared mapper, JADE plasma analyser, JEDI energetic-particle detector, UVS ultraviolet spectrograph, JunoCam visible-light camera (citizen-science image processing).
Juno's science discoveries are extensive. The MWR radiometer revealed the gas giant's deep ammonia layer + downdrafts. The MAG magnetometer mapped the planet's bizarre quadrupolar magnetic field — far more complex than predicted by pre-Juno models. Gravity-science measurements revealed the gas giant's heavy-element core is partially-mixed with the hydrogen envelope rather than discrete-layered. JunoCam citizen-science processed thousands of public images of the planet's atmosphere + the Great Red Spot. Juno's mission was extended to 2025 (planned end of mission with atmospheric entry) + then extended again to 2026 + (likely) end-of-mission late 2026. The mission has produced 300+ peer-reviewed scientific papers + transformed Jovian science.
For Kids — a shorter, friendlier version
The Juno is a NASA spacecraft that flies around the planet Jupiter. Lockheed Martin built Juno for NASA's New Frontiers Program. Juno launched in August 2011 and arrived at Jupiter on July 4, 2016, after a 5-year cruise. Juno has been orbiting Jupiter ever since.
Juno is solar-powered, with three huge solar panels. Each panel is about the size of a school bus side. Together they make 500 watts of power at Jupiter, enough for the spacecraft's instruments. Juno is the farthest solar-powered spacecraft ever flown.
Juno carries many instruments to study Jupiter. The magnetometer maps the planet's magnetic field. The microwave radiometer looks under the cloud tops. The JunoCam takes color pictures of the planet, which the public can process online. At closest approach to Jupiter, Juno reaches 129,000 mph, much faster than a rifle bullet.
Juno has made many discoveries. The magnetic field is unusual: more bumpy and complex than expected. The planet has a deep, partly-mixed core, not a clean solid one. The atmosphere has powerful storms reaching deep below the cloud tops. Juno keeps flying and sending back new data every few months.
Fun Facts
- Juno is a NASA spacecraft orbiting Jupiter since July 2016.
- Juno is the farthest solar-powered spacecraft ever flown.
- Each solar panel is about the size of a school bus side.
- Juno reaches 129,000 mph at closest approach, much faster than a rifle bullet.
- Juno has done about 70 close flybys of Jupiter through 2026.
- The JunoCam takes color pictures the public can process online.
- Juno found that Jupiter has a partly-mixed core, not a clean solid one.
Kids’ Questions
Why solar power so far from the Sun?
Most spacecraft going past Mars use small nuclear power supplies, because sunlight gets weak farther out. Juno uses huge solar panels instead: each one is about the size of a school bus side. At Jupiter, the panels still make 500 watts, enough for the spacecraft. This was the first time solar power was used at Jupiter's distance. Future Jupiter spacecraft may go back to nuclear power.
What is JunoCam?
JunoCam is a color camera on Juno that takes pictures of Jupiter. The unique part: NASA does not process the pictures into final images. Instead, raw photos are posted online, and anyone can download them and process them into art. Many amateur image-processors have made stunning views of Jupiter from JunoCam data. This is the first NASA mission with citizen science on camera images.
What did Juno find?
Juno made many surprising discoveries. The magnetic field is bumpy and complex, not smooth as expected. The deep interior has a fuzzy partly-mixed core, not a clean solid one. The atmosphere has Earth-sized cyclones at the poles. Lightning happens at the cloud tops, not deep down. Juno keeps making new discoveries on each close flyby of Jupiter.
Variants
- Juno (single mission)
- Unique spacecraft. Jupiter orbit since 2016.
Notable Operators
- NASA New Frontiers Program (2011-present)
- Sole operator. JPL mission control + Lockheed Martin spacecraft.
Frequently Asked Questions
Why is Juno solar-powered at Jupiter?
Most outer-planets missions use plutonium-238 radioisotope thermoelectric generators (RTGs) because solar power becomes very weak in the Jovian system (~25× less sunlight than at Earth). NASA had limited Pu-238 supply in 2003-2011 (the US restarted Pu-238 production only in 2015), so Juno was designed solar-powered to conserve Pu-238 for higher-priority missions (Mars 2020, Dragonfly, Europa Clipper). Juno's 60 m² of solar panels (the largest of any deep-space spacecraft) generate ~500 W in orbit — enough for science instruments + spacecraft systems but only for short windows around perijove (closest approach). Juno orbits in a highly-elliptical 53-day orbit to minimise radiation exposure to its electronics + to conserve power. Juno demonstrated that solar power is feasible at the gas giant — a precedent for future cost-controlled outer-planets missions.