Despite fears of radiation damage or a possibly crippling high-speed impact with debris in Jupiter's tenuous ring, NASA's Juno probe safely braked into orbit around the giant planet late Monday, firing its main engine for 35 tense minutes to slow down enough to be captured in the planned polar orbit, elated mission managers said Tuesday.
Because of Jupiter's distance from Earth -- 540 million miles -- flight controllers at NASA's Jet Propulsion Laboratory could not follow along in real-time, they had to wait 48 minutes for radio signals to cross the vast gulf, confirming the start of the burn. And by that time, it was already over.
It was a tense few minutes for the hundreds of men and women who spent more than 10 years planning Juno's long-awaited mission. If the motor failed to fire, or if it shut down before the 20-minute mark, the $1.1 billion mission would have been a write-off.
But in the end, diagnostic tones radioed back to Earth showed the rocket motor fired and shut down right on time, putting the spacecraft into an initial 53.5-day orbit around Jupiter's poles. Shortly after the engine shut down, the probe turned to point its solar arrays back at the sun.
"NASA did it again! That says it all to me," Scott Bolton, the Juno principal investigator, exclaimed at a post orbit-insertion news conference. "And I am so happy to be part of the team that did that. This team has worked so hard, and we have just such great people. It's almost like a dream coming true right here. ... And now the fun begins. The science!"
Speaking of the diagnostic tones sent back from Juno to mark major events during the critical rocket firing, Rick Nybakken, the Juno project manager, said "tonight through tones, Juno sang to us. And it was a song to perfection."
"After a 1.7-billion-mile journey, we hit our burn targets within one second on a target (in space) that was just tens of kilometers large," he said. "Isn't that incredible? That's how good our team is, and that's how well the Juno spacecraft performed tonight."
The critical burn began at 10:30 p.m. EDT (GMT-4) and ended at 11:05 p.m. Signals confirming the start of the burn reached JPL at 11:18 p.m. triggering a round of applause. Finally, at 11:53 p.m., the tones showed an on-time engine shutdown, prompting a more vocal round of cheering, hugs and high fives.
"We have the tones for burn cutoff on delta-V," an engineer told the team. "Welcome to Jupiter!"
A few moments later, the propulsion officer added the burn lasted 2,102 seconds, "only differing one second off of the pre-burn predictions." Then he added his own "welcome to Jupiter!"
Said Bolton, with a bit of understandable overstatement: "Everybody, you're the best team ever! You just did the hardest thing NASA's ever done! That's my claim."
"The spacecraft performed extremely well," said Guy Beutelschies, director of space exploration systems at spacecraft-builder Lockheed Martin. "We've got the spacecraft back pointed at the sun and the antenna back on Earth. We're starting to get the higher-rate data down and so we've got a long night ahead of us. We're going to be going through that data in meticulous detail to make sure the spacecraft is healthy."
But an initial review of the data indicated "the spacecraft is performing well," he said. "It did everything it needed to do, and so we're very pleased."
President Obama tweeted an enthusiastic response:
Incredible! After a 5-year journey, we're up close and personal with our solar system's largest planet. Welcome to Jupiter, @NASAJuno!— President Obama (@POTUS) July 5, 2016
Over its next 20 months in orbit around Jupiter, Juno could help shed light on the formation of our solar system and other planets as well. "Jupiter is a really wonderful place for us to understand how our solar system formed," Derrick Pitts, chief astronomer of the Franklin Institute in Philadelphia, told "CBS This Morning" Tuesday. "It has so much material left over from the early history of the solar system that we can use it as like a museum of the solar system."
Juno's science instruments and camera were turned off several days before the Jupiter orbit insertion rocket firing to simplify spacecraft operations during a mission-critical sequence of events. But before it was turned off, JunoCam, the spacecraft's primary camera, captured images that were assembled into an approach movie covering 17 days.
Bolton unveiled the three-minute video at the news conference, showing a half-full Jupiter and the four large Galilean moons, Io, Europa, Ganymede and Callisto, wheeling about in their orbits, winking in and out of view as they passed behind the planet and through its shadow.
While photos of Jupiter and its four brightest moon are commonplace -- the moons can be seen in binoculars -- Juno's movie is the first to show a closeup view of the satellites in motion from the perspective of a nearby visitor.
"Juno on its approach managed to capture a movie of Jupiter and its moons, and for the first time, all of us together will actually see the true harmony in nature," Bolton said before showing off the video clip. "This is what's it's about, this is what Jupiter and its moons look like, this is what our solar system looks like if you were to move out, it's what the galaxy looks like. ... It's harmony at every scale."
Launched on Aug. 5, 2011, Juno needed five years to reach the solar system's largest planet, looping out beyond the orbit of Mars before zooming back past Earth in October 2013 for a velocity-boosting gravity-assist flyby that pumped up its velocity enough to head for Jupiter.
The first solar-powered spacecraft to venture so far into deep space, Juno braked into an initial 53.5-day orbit around the planet's poles, reaching a record velocity of some 130,000 mph relative to Jupiter. The orbit will be shortened to 14 days in October, setting up repeated low-altitude passes within a few thousand miles of Jupiter's turbulent atmosphere.
As it flies past, sensitive instruments will measure the planet's powerful magnetic field, and radiation belts, look for signs of the dynamo powering the field, map out its gravity and look for telltale signs of water in its atmosphere that might indicate where in the solar system Jupiter originally formed.
The spacecraft also will search for Jupiter's unseen core, if it has one, and perhaps help scientists understand what is powering its great red spot, a huge cyclone that has persisted for hundreds of years.
"We've flown by Jupiter with the two Pioneers and the two Voyagers and we've had Galileo in orbit (in the 1990s)," Jim Green, director of planetary science at NASA Headquarters, said earlier Monday. "But ... studying the planet has only really been done skin deep. Juno, on the other hand, is going to be flying right over the cloud tops, and it has a wonderful opportunity to actually peer inside it."
Jupiter, Green said, "is sort of like a cake that's still cooling off after you've baked it. It's an enormous planet, it's hung on to all the original material in our collapsing cloud. And so by interrogating it, understanding its pressure density and temperature we can really get a good idea on how it was put together."
"We want to know, for instance, is the core in the center of Jupiter a solid, rocky core? Or more of a gaseous core under huge pressures? This tells us whether Jupiter was actually formed first of all our planets or perhaps started out with a rocky core, which must have been created first. So it's all about understanding the order of the evolution of our planets and the composition of the cloud that collapsed creating them."