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Juno spacecraft in Jupiter's orbit

July 5, 2016

The Juno spacecraft has reached Jupiter after a journey at 200 times the speed of sound. NASA scientists hit the brakes at just the right time to pull the spacecraft into Jupiter's orbit.

NASA Juno Sonde am Jupiter Illustration
Image: NASA/JPL-Caltech

The moment of truth came at 12 midnight EDT (04:00 GMT/UTC) on Tuesday.

Juno's principal investigator Scott Bolton, at the Southwest Research Institute in San Antonio, Texas, had admitted to being "nervous" and "scared" about the fate of the $1.1 billion (1 billion euro) spacecraft, which was traveling at a speed of more than 150,000 miles per hour (250,000 kmph) toward what he called "the king of the solar system."

Juno slowed down in order to be captured by Jupiter's gravity and pulled into its orbit 3,000 miles (5,000 kilometers) above the clouds. Juno was precisely positioned, ignited its main engine at exactly the right moment and kept it burning for 35 minutes to lose enough speed.

Infografik Verstärkte Strahlung um Jupiter ENGLISCH

Throughout its 37 orbits, over 20 months, Juno's titanium cover must endure massive amounts of radiation - the equivalent of 100 million dental x-rays.

Ultimately a suicide mission

Juno's aim is to map Jupiter's gravity and magnetic fields, and determine whether the planet has a dense core beneath its clouds. For its grand finale - its final orbit - Juno will dive into Jupiter's atmosphere, where it will be crushed and vaporized.

Among the questions scientists Juno will help answer are: How much water exists? Is there a solid core? Why are Jupiter's southern and northern lights the brightest in the solar system?

"What Juno's about is looking beneath that surface," Bolton said. "We've got to go down and look at what's inside, see how it's built, how deep these features go, learn about its real secrets."

There's also the mystery of its Great Red Spot, which appears to be a massive, centuries-old storm which is larger than the earth.

Juno is the first spacecraft to travel so far out powered by the sun, beating Europe's comet-chasing Rosetta spacecraft. Three massive solar wings stick out from Juno like blades from a windmill. They house 18,698 solar cells, which generate 500 watts of power to run its nine instruments.

Jupiter's sheer size gives it immense gravity, which it exerts by packing two-and-a-half times the mass of all the other planets in our solar system combined.

Its mass and gravitational force is believed to have helped shield Earth from bombardment of comets and asteroids - an astronomical lightning rod, so to speak.

bik/jm (AP, Reuters, AFP)