Juno Spacecraft

Juno is a space probe launched by NASA as part of its New Frontiers program to study the planet Jupiter. Launched on 5 August 2011 and entering Jupiter’s orbit on 5 July 2016, Juno’s primary objective is to understand the planet’s formation, structure, atmosphere and magnetosphere. Juno stands out as the first spacecraft to operate in a unique polar orbit passing over Jupiter’s poles and to use solar panels as its main power source in the outer Solar System.

Juno Spacecraft - Anadolu Agency

Mission Objectives

Juno’s scientific goals are focused on answering fundamental questions about Jupiter’s origin and evolution:

• Formation: Test theories of planetary formation by measuring the amounts of water and ammonia in Jupiter’s atmosphere.
• Structure: Determine whether Jupiter has a solid core by precisely mapping its mass distribution, gravity field and magnetic field.
• Atmosphere: Investigate the composition, temperature, cloud motions and other properties in the deep atmosphere.
• Magnetosphere: Study the origin of Jupiter’s immense magnetic field and the processes that generate its polar auroras.

Design and Hardware

Overall Structure

Juno has a hexagonal main body that rotates around its own axis to maintain stability during the mission. A titanium radiation shield (Juno Radiation Vault) protects the probe’s sensitive electronic components from Jupiter’s intense radiation belts.

Power Source

The most distinctive feature of Juno compared to previous outer planet missions is its use of massive solar panels instead of radioisotope thermoelectric generators (RTGs) for power. Three large solar panels, each approximately nine meters long, are designed to provide sufficient power to the spacecraft despite receiving less than 4 percent of the sunlight available at Earth’s orbit. This represents a major achievement in spacecraft engineering.

Scientific Instruments

Juno is equipped with nine primary scientific instruments to achieve its mission objectives:

• Microwave Radiometer (MWR): Probes deep into Jupiter’s atmosphere to study the structure and dynamics of ammonia and water.
• Jovian Infrared Auroral Mapper (JIRAM): Investigates auroras and chemical composition in the upper layers of the planet’s atmosphere.
• Magnetometer (MAG): Maps Jupiter’s powerful magnetic field with high precision.
• Gravity Science (GS): Helps determine the planet’s internal mass distribution by tracking subtle changes in the probe’s orbit.
• JunoCam: A visible-light camera open to public participation.

Mission Timeline

Launch and Cruise

Juno was launched on 5 August 2011 from Cape Canaveral Space Force Station in Florida aboard a Atlas V rocket. It undertook a five-year journey to reach Jupiter, during which it performed a gravity assist maneuver around Earth in October 2013 to gain speed.

Jupiter Orbit Insertion and Science Operations

On 5 July 2016, Juno successfully executed a critical maneuver by firing its main engine for 35 minutes to enter orbit around Jupiter. The spacecraft settled into a highly elliptical polar orbit with a 53-day period. This orbit allows Juno to approach within about 4,200 kilometers of Jupiter’s cloud tops during each “perijove” (closest approach), while simultaneously avoiding the planet’s most hazardous radiation belts.

Mission Extension

Having successfully completed its primary mission, Juno’s operations have been extended by NASA. This extended mission not only continues studying Jupiter but also includes close flybys of its moons Ganymede, Europa and Io.

Key Discoveries

• Polar Cyclones: Juno discovered massive, persistent clusters of cyclones at Jupiter’s north and south poles, forming geometric patterns never seen before.
• Atmospheric Depth: It revealed that the Great Red Spot extends hundreds of kilometers below the cloud tops and that Jupiter’s atmosphere is much deeper than previously expected.
• “Shallow Lightning” and Ammonia Hail: Juno found that Jupiter’s lightning occurs in shallow clouds containing “mushballs” — mixtures of ammonia and water — unlike Earth’s lightning, which forms in deeper water clouds.
• Magnetic Field: Jupiter’s magnetic field was found to be far more complex than previously modeled, with some regions significantly stronger and others weaker than expected.