After a journey of nearly five years, topped off by a dramatic burst of pyrotechnics, NASA’s Juno mission has arrived at Jupiter.

The spacecraft was moving at over 200,000 kilometres per hour when it reached its destination Monday night and executed a nail-biting hairpin turn that sent it on a pole to pole swing around the planet.

Ivan Semeniuk explains importance of Juno probe’s approach to Jupiter (The Globe and Mail)

Engineers and scientists at the Jet Propulsion Laboratory in Pasadena, Calif., erupted in cheers at 8:53 p.m. PT, when the probe signaled that it had completed a crucial 35-minute engine burn that placed it in orbit around Jupiter. The preprogrammed maneuver was designed to slow the probe just enough to allow it to be snared by the giant planet’s gravity.

“Welcome to Jupiter,” mission controllers announced as team members leaped to their feet, applauded and shook hands.

The success means that scientists can now gear up for a planned 18-month survey of Jupiter, which they hope will reveal new information about the giant planet’s internal structure and formation history.

Juno’s arrival — technically referred to as “Jupiter orbit insertion” — unfolded flawlessly despite worries that high energy particles trapped in the planet’s magnetic field might affect the spacecraft, potentially causing its computer to reboot at an inopportune moment. To help guard against this, Juno’s electronics are protected inside a thick-walled platinum box that engineers have dubbed “the vault.” But while the shielding is essential for the spacecraft’s survival, it cannot block every particle Juno encounters.

As an additional precaution, Juno’s science instruments were shut off a few days before its arrival so, as expected, there were no pictures to show of the spacecraft’s first encounter.

At a late night press briefing, Scott Bolton, the mission’s principal investigator, unveiled a time-lapse video made over a 17-day period as Juno approached the Jupiter system. Recalling the discoveries of the astronomer Galileo, who first spotted Jupiter’s four largest moons through his telescope in 1610, the time-lapse sequence shows the moons racing around the giant planet much as Galileo once saw them, but from a very different angle.

Juno is now moving away from Jupiter on a highly elongated 53-day orbit that will next bring it in close proximity to the planet on August 27. At that point, scientists will have their first chance to gather images and data while the spacecraft passes within 4,500 km of Jupiter’s colourful cloud tops.

Later this year the spacecraft will shift to a 14-day orbit to increase the pace at which it can gather its science.

Juno was launched in 2011 and is the first spacecraft equipped to study Jupiter’s interior. Over the coming months it will study the planet’s gravitational and magnetic fields and use microwaves to probe deep into its cloud layers to measure water abundance and other constituents.

It is also the first spacecraft to venture into the outer solar system while using only the sun to power its instruments and on-board systems. It carries three massive solar panels, each about nine metres long, to gather enough energy to fulfill its goals.

During orbit insertion, Juno had to turn away from the sun and run on battery power. Mission controllers breathed an additional sign of relief about 45 minutes after the engine burn when the panels were rotated toward the sun.

“The more you know about the mission, the more you know just how tricky this was,” said Juno program executive Diane Brown. “To know that we can all go to bed tonight not worried about what’s going to happen tomorrow — that’s pretty awesome.”

At the news briefing Dr. Bolton put it more succinctly.

“We’re in!” he said. “Now the fun begins.”

The Globe and Mail
Published Tuesday, Jul. 05, 2016 12:08AM EDT
Last updated Tuesday, Jul. 05, 2016 2:55AM EDT