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Juno probe successfully enters Jupiter's orbit after 'amazing' mission

After a five year journey from Earth, Juno the solar-powered spacecraft squeezed through a narrow band, skimming Jupiter’s surface, avoiding the worst of both its radiation belt and its dangerous dust rings.

It fired its main engine, slowing its velocity, and allowing it to get captured into Jupiter’s hefty orbit.

After it was complete, jubilant scientists fronted a press conference, and tore up a “contingency communication strategy” they said they prepared in case things went wrong.

“To know we can go to bed tonight not worrying about what is going to happen tomorrow, is just amazing,” said Diane Brown, a project manager from NASA’s Jet Propulsion Laboratory.

Scott Bolton, principle investigator of the Juno mission told his colleagues: “You’re the best team ever! We just did the hardest thing Nasa has ever done.”

Now the spacecraft will orbit the planet once every 53 days until October 14, when it will shift to a tighter 14-day orbit. And after about 20 months of learning everything it can about Jupiter’s interior and its atmosphere, it will eventually succumb to the harsh environment and plunge into the planet’s crushing centre.

But right now all that is ahead of us. We watch wide-eyed, eager to learn about the giant planet, and in doing so, learn more about how we all got here.

The Juno spacecraft launched aboard an Atlas V-551 rocket from Cape Canaveral, Fla., on Aug. 5, 2011, and will reach Jupiter in July 2016. The spacecraft will orbit Jupiter 32 times, skimming to within 3,100 miles (5,000 kilometers) above the planet's cloud tops, for approximately one year.

Juno uses a spinning solar-powered spacecraft in a highly elliptical polar orbit that avoids most of Jupiter's high radiation regions. The designs of the individual instruments are straightforward and the mission does not require the development of any new technologies.

Artist's rendering of Juno spacecraft with human figure for scale and descriptions of science instruments.

Juno spacecraft and its science instruments. Image credit: NASA/JPL
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Juno's scientific payload includes:

A gravity/radio science system (Gravity Science)
A six-wavelength microwave radiometer for atmospheric sounding and composition (MWR)
A vector magnetometer (MAG)
Plasma and energetic particle detectors (JADE and JEDI)
A radio/plasma wave experiment (Waves)
An ultraviolet imager/spectrometer (UVS)
An infrared imager/spectrometer (JIRAM)
The spacecraft will also carry a color camera, called JunoCam, to provide the public with the first detailed glimpse of Jupiter's poles.

Rotating Spacecraft

For Juno, like NASA’s earlier Pioneer spacecraft, spinning makes the spacecraft's pointing extremely stable and easy to control. Just after launch, and before its solar arrays are deployed, Juno will be spun-up by rocket motors on its still attached second-stage rocket booster. While in orbit at Jupiter, the spinning spacecraft sweeps the fields of view of its instruments through space once for each rotation. At three rotations per minute, the instruments' fields of view sweep across Jupiter about 400 times in the two hours it takes to fly from pole to pole.

Solar Power

Jupiter’s orbit is five times farther from the Sun than Earth’s, so the giant planet receives 25 times less sunlight than Earth. Juno will be the first solar-powered spacecraft designed by NASA to operate at such a great distance from the sun, thus the surface area of solar panels required to generate adequate power is quite large. Three solar panels extend outward from Juno’s hexagonal body, giving the overall spacecraft a span of about 66 feet (20 meters). The solar panels will remain in sunlight continuously from launch through end of mission, except for a few minutes during the Earth flyby. Before launch, the solar panels will be folded into four-hinged segments so that the spacecraft can fit into the launch vehicle.

Juno benefits from advances in solar cell design with modern cells that are 50 percent more efficient and radiation tolerant than silicon cells available for space missions 20 years ago. The mission’s power needs are modest, with science instruments requiring full power for only about six hours out of each 11-day orbit (during the period near closest approach to the planet). With a mission design that avoids any eclipses by Jupiter, minimizes damaging radiation exposure and allows all science measurements to be taken with the solar panels facing the sun, solar power is a perfect fit for Juno.

Electronics Vault

Juno will avoid Jupiter's highest radiation regions by approaching over the north, dropping to an altitude below the planet's radiation belts – which are analogous to Earth’s Van Allen belts, but far more deadly – and then exiting over the south. To protect sensitive spacecraft electronics, Juno will carry the first radiation shielded electronics vault, a critical feature for enabling sustained exploration in such a heavy radiation environment. This feature of the mission is relevant to NASA's Vision for Space Exploration, which addresses the need for protection against harsh radiation in space environments beyond the safety of low-Earth orbit.

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