NASA's Juno spacecraft getting close to Jupiter

After a journey of more than five years, U.S. space agency NASA's Juno spaceship is set to reach its final destination Jupiter and begin its orbit around the largest planet in our solar system.

According to NASA's Jet Propulsion Laboratory (JPL), the probe will fire its main engine, beginning a 35-minute burn at 8:18 p.m. PDT (0318 GMT) on the evening of July 4 to be captured by Jupiter's gravity and go into the desired orbit.

"We are ready," Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. "The engineers and mission controllers are performing at an Olympic level getting Juno successfully into orbit," he said in a statement on Saturday.

After the main engine burn, Juno will be in orbit around Jupiter. The spacecraft will spin down from 5 to 2 RPM, turn back toward the sun, and ultimately transmit telemetry via its high-gain antenna.

On Sunday, the solar-powered spacecraft crossed the orbit of Callisto, the outermost Galilean moon. The orbits of Ganymede, Europa and Io will be crossed on Monday. These four largest moons of Jupiter are named the Galilean moons because they were discovered by Galileo Galilei in 1609.

Assuming all goes smoothly, the 1.1 billion U.S. dollars mission will provide a lot answers to questions about Jupiter and help reveal a lot about the other planets in our solar system, including Earth.

Although it's well-known that the gas giant is made up primarily of hydrogen and helium gas, the planet's core remains mysterious.

"As Juno barrels down on Jupiter, the scientists are busy looking at the amazing approach science the spacecraft has already returned to Earth. Jupiter is spectacular from afar and will be absolutely breathtaking from close up," Bolton said.

During its mission of exploration, Juno will circle Jupiter 37 times, soaring low over the planet's cloud tops, as close as about 4,100 kilometers.

During these close passes, Juno's instruments will be collecting data and probe beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet's origins, structure, atmosphere and magnetosphere.

But before Juno can collect the data Lunine and other scientists are looking forward to, the space probe has to get into orbit. Even if everything goes well, orbiting near Jupiter is hazardous.

The planet is surrounded by powerful radiation that can fry any spacecraft that comes too near. It's spinning around so fast. Its gravity is like a giant sling shot, slinging rocks, dust, electrons, whole comets. Anything that gets close to it becomes its weapon.

"No spacecraft has ever flown this close to Jupiter. And the first time we go in, that's the most dangerous. We call it Jupiter Orbit Insertion," NASA said in a video.

"So the real trick is. We're going to go in close, get the data and get out." Endit