The Juno space probe is still millions of kilometers and 18 days away from Jupiter, but on July 4, the spacecraft will fire its main engine for 35 minutes as it enters a polar orbit around the gas giant.
The probe, which is the size of a basketball court, will skim the planet's clouds, eventually coming within 4,667 kilometers of Jupiter as it attempts to get a look under the massive planet’s thick cloud cover, hopefully leading to better insight on the planet’s “origins, structure, atmosphere and magnetosphere.”
"At this time last year our New Horizons spacecraft was closing in for humanity's first close views of Pluto," said Diane Brown, Juno program executive at NASA Headquarters in Washington. "Now, Juno is poised to go closer to Jupiter than any spacecraft ever before to unlock the mysteries of what lies within."
During the entire mission, Juno will make 37 “close approaches” to Jupiter, and each one could imperil the craft. For example, under the clouds, there is a layer of hydrogen under so much pressure that it conducts electricity. That, along with the planet’s fast rotation [one day on Jupiter is only 10 hours long], creates a strong magnetic field, creating what NASA calls the “harshest radiation environment in the solar system.”
"Over the life of the mission, Juno will be exposed to the equivalent of over 100 million dental X-rays," said Rick Nybakken, Juno's project manager from NASA's Jet Propulsion Laboratory in Pasadena, California. "But, we are ready. We designed an orbit around Jupiter that minimizes exposure to Jupiter's harsh radiation environment. This orbit allows us to survive long enough to obtain the tantalizing science data that we have traveled so far to get."
Juno is also fitted with “radiation-hardened electrical wiring and shielding” as well as a unique titanium vault that protects the probe’s most vital equipment, such as the flight computer. The vault is so strong that it will reduce radiation exposure by 800 times. Without it, “Juno's electronic brain would more than likely fry before the end of the very first flyby of the planet.”
Juno launched on August 5, 2011 from Cape Canaveral, Florida. Its July 4 arrival in orbit around Jupiter coincides with the U.S. independence holiday which is celebrated with fireworks displays.
Watch a video on the Juno mission: