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Return to Jupiter - the Juno mission

Paul Sutherland, Feature writer
Aug 5, 2011, 7:00 UTC

Sen—NASA is heading back to Jupiter with the launch of a new probe, Juno, that will explore the giant planet of the Solar System.

After blasting off aboard an Atlas V rocket from Cape Canaveral, Florida, the unmanned craft will spend five years zipping among the planets to build up momentum before reaching its distant destination in 2016.

The $700 million (£430 million) mission will orbit gas-ball Jupiter from pole to pole, hugging the planet close and braving its deadly radiation. But its instruments will be able to penetrate deep into its dense clouds to find out what it is made of.

Jupiter is so massive that it two and a half times the size of all the other planets, moons and asteroids put together. With a diameter at the equator of 143,000 km, it is as big 1,300 Earths and so holds most of the material that was left in the Solar System after the Sun formed four billion years ago. 

Space scientists believe it will therefore give them vital clues about the Solar System’s origins after the Sun condensed from a vast cloud of gas and dust. Jupiter’s size also gives it enormous influence over other bodies and it has swept up many asteroids and comets that might otherwise have hit us.

NASA's Scott Bolton, principal scientist on the mission, told Sen: "Jupiter holds secrets about how the solar system formed. We want to get the list of ingredients that produced the recipe for planets."

Jupiter is of further special interest because most of the planets recently discovered to be orbiting other stars have turned out to be giant gas worlds too. They have been dubbed “hot Jupiters” because they tend to be found orbiting very close to their parent stars. NASA is keen to learn therefore why Jupiter itself sits at a much greater distance of around 778,330,000 km from the Sun. Indeed evidence from its chemical make-up suggests that it formed in an even colder region of space and so may have moved into the Solar System from the outer fringes.

Jupiter, which is largely made up of hydrogen and helium, has previously been visited by other spaceprobes, notably Galileo which was launched from the Space Shuttle and orbited the planet from December 1995 to September 2003. Pioneers 10 and 11 and Voyagers 1 and 2 previously flew past it and Ulysses, Cassini and New Horizons have sped by since.

Juno’s mission will be quite different to Galileo’s because the earlier probe orbited around Jupiter’s equator. Juno will fly from pole to pole and be able to scan the entire planet in its time of operation, including its famous Great Red Spot, a massive storm that has been raging for centuries. Galileo fired a probe into Jupiter’s cloud belts that failed to detect water expected to be there. Juno’s instruments will be able to take soundings deep into the atmosphere and find the water. 

Juno's sensitive electronics will be shielded inside a titanium vault with walls nearly half an inch thick to protect them from being fried. But the mission at Jupiter is still expected to last only a year as it is bombarded by radiation levels equal to 100 million dental X-rays. That will allow 33 orbits and the NASA scientists are confident they will scan the whole planet in that time.

The probe will be 20 meters wide with its giant solar panels fully extended. It will spin slowly so that the various instruments on board each get a chance to view the mighty planet. One, the JunoCam, will send back colour photos of the planet. Others will study the upper atmosphere and lower cloud levels, Jupiter’s magnetic field, which is the most intense of any planet, and aurorae, and its gravity field to help work out what lies at Jupiter’s centre.

Dr Bolton, of the Southwest Research Institute at San Antonio, Texas, told Sen: “We're basically cartwheeling through space and the instruments are all looking out between the solar arrays and as we spin everyone gets a chance to look down on Jupiter. 

“On previous missions there were complex scan platforms to turn instruments and those were very operationally complex. Ours is very simple and straightforward, very repetitive because we designed it that way. Part of that is from lessons learned and partly it was because we were trying to do things with a much lower budget.”

Dr Bolton, who also worked on the Voyager, Galileo and Cassini missions, added: “In some ways missions today are more complex and in other ways they're simpler. We doing things really smart and integrated with Juno so we are able to accomplish an enormous amount more efficiently than Galileo and Cassini could. And our instruments are more sophisticated and they're much more precise than was available on earlier missions. So we've improved the technology and we've also fine-tuned our questions.”

As well as the scientific instruments, Juno carries three tiny “passengers” - LEGO plastic models of the Roman god Jupiter, his wife Juno after whom the probe is named, and the Italian astronomer who used one of the earliest telescopes to observe the planets and discover its four main moons. The 1.5 inch high figurines have been placed on board to inspire youngsters about science, space and engineering. There is also a tiny aluminium plaque dedicated to Galileo, supplied by the Italian Space Agency.

Juno is a budget mission by NASA standards and the second in its New Frontiers programme. But if all goes to plan, it will reap a harvest of new knowledge about Jupiter that will keep planetary scientists busy for years.