Anticipation reached cosmic proportions Monday for the Southern California scientists who are part of the team behind a NASA mission to Jupiter.
The encounter between Juno and Jupiter was on schedule to occur Monday evening, marking a harrowing end to the spacecraft's five-year journey through space. Juno will need to slow down to enter the proper orbit -- too fast or too slow, and it could miss its target.
Scientists said at a Monday morning news conference that they've done everything possible to make the mission a success.
"I'm incredibly thrilled, but it is a little surreal," said Rick Nybakken, Juno project manager from Southern California's Jet Propulsion Laboratory. "It's hard to believe today's the day."
That excitement has been building since Juno launched from Cape Canaveral in August 2011 on a long and increasingly strange trip that will put the orbiter through a harrowing approach to Jupiter. NASA and the Jet Propulsion Laboratory in Southern California even produced a Hollywood-style trailer to illustrate the perils that await as Juno fires its main engine to slow down and moves into place to begin its orbit around the fifth planet from the sun.
It will be a delicate, precisely calculated one-shot move, expected to happen Monday night. NASA coverage is expected to begin around 7:30 p.m. (10:30 p.m. ET)
"I'm torn with the incredible excitement and anticipation, with 'Oh, my God. We're going in. It's really happening,'" said Dr. Scott Bolton, the mission's principal investigator.
Once in place, Juno will begin circling Jupiter's poles and peering through clouds to study how the planet formed and evolved. Unlike Earth, which is a rocky planet, Jupiter is a gas giant made up mostly of hydrogen and helium.
"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."
Previous missions to Jupiter have relied on nuclear power sources this far out from the sun. Juno is unique because it has solar panels that are designed to face the sun during most of the mission.
It will orbit the planet for 20 months — that's 37 times around — before ending its mission in February 2018. After all that, the orbiter will simply burn up as it soars toward the planet's surface.
Juno's instruments are protected from radiation by a titanium vault.
"Juno is going to go into the scariest part in the scariest place that we know about -- because we don't know about it," said Heidi Becker, lead investigator from JPL. "There are high energy electrons that are so energetic they're moving at the speed of light. They will go right through a spacecraft... and fry your brain if you don't do anything about it."
It also is equipped with a camera, which should provide stunning views if previous missions are any indication.
Previous Jupiter visits showed its signature Great Red Spot, a long-lived storm, and its many moons. The Galileo mission dropped a probe on the planet's surface and conducted 14 years of exploration.
But many questions remain, such as whether Jupiter has a solid core and how much oxygen and water are present.
The Associated Press contributed to this report.