Jupiter-bound craft runs into problem after flyby (Update)

Oct 09, 2013 by Alicia Chang
This 2010 artist's rendering depicts NASA's Juno spacecraft with Jupiter in the background. NASA's Jupiter-bound spacecraft will swing by Earth for one last visit Wednesday Oct. 9, 2013 before speeding to the outer solar system. Wednesday's flyby allows the Juno spacecraft to gather the momentum it needs to arrive at Jupiter in 2016. (AP Photo/NASA/JPL, File)

NASA's Jupiter-bound spacecraft hit a snag Wednesday soon after it used Earth as a gravity slingshot to hurtle toward the outer solar system, but mission managers said it's on course to arrive at the giant planet in 2016.

Juno emerged from Earth's shadow in safe mode, a state that spacecraft are programmed to go into when there's some trouble.

Despite the problem, "we believe we are on track as planned to Jupiter," said project manager Rick Nybakken of the NASA Jet Propulsion Laboratory, which manages the $1.1 billion mission.

Engineers continued to diagnose the issue, which occurred after Juno whipped around Earth in a momentum-gathering flyby. Up until Wednesday, Juno had been in excellent health. While in safe mode, it can communicate with ground controllers, but its activities are limited.

Previous missions to the outer solar system have used Earth as a celestial springboard since there's no rocket powerful enough to make a direct flight. The Galileo spacecraft buzzed by Earth twice in the 1990s en route to Jupiter, the solar system's largest planet located 484 million miles from the sun.

Launched in 2011, Juno flew beyond the orbit of Mars, Earth's closest planetary neighbor, before looping back toward our home planet for a quick visit. Wednesday's rendezvous boosted Juno's speed from 78,000 mph (125,523 kph) relative to the sun to 87,000 mph—enough momentum to cruise past the asteroid belt to Jupiter, where it should arrive in 2016.

During the swing past Earth, Juno snapped pictures. The solar-powered, windmill-shaped spacecraft slipped into Earth's shadow as planned, but engineers were puzzled by the too little data it sent back afterward. At closest approach, it hurtled 350 miles above the ocean off the coast of South Africa.

NASA said skywatchers with binoculars or a small telescope might have seen it streak across the sky, weather permitting. Ham radio operators around the globe were encouraged to say "Hi" in Morse code—a message that might be detected by Juno's radio.

By space mission standards, Juno's Earth rendezvous was low-key compared with the Curiosity rover's nail-biting landing on Mars last year, which drew crowds. Since flybys have been executed before, project managers predicted a smooth flight.

The unexpected problem causes "a moderate level of concern," Nybakken said.

Despite a government shutdown that has prevented NASA from updating its website or tweeting, the space agency's missions continue to operate. Earlier this week, NASA's newest spacecraft, LADEE, slipped into orbit around the moon.

Since the 1970s, spacecraft have circled or flown past Jupiter including the Voyagers, Pioneers, Galileo, Ulysses, Cassini and, most recently, the New Horizons barreling toward Pluto. Missions have beamed back stunning views of Jupiter's trademark Great Red Spot, a raging hurricane-like storm, and its many moons.

Juno promises to inch closer to Jupiter than previous spacecraft, orbiting the planet for at least a year and studying its cloud-covered atmosphere and mysterious interior to better understand how the giant planet formed.

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GSwift7
not rated yet Oct 10, 2013
Previous missions to the outer solar system have used Earth as a celestial springboard since there's no rocket powerful enough to make a direct flight


The New Horizons mission was launched on a direct solar escape trajectory from Earth. It is the first time it was done, but that statement from the article is incorrect.

http://en.wikiped...Horizons

They used an Atlas V-551 launch vehicle.

lol, they even mention New Horizons in the article.
yyz
not rated yet Oct 10, 2013
Well, even New Horizons needed a gravity assist to reach its primary target, Pluto: http://en.wikiped...y_assist

As for previous missions to the outer solar system (as noted in my link) both New Horizons and Ulysses were launched directly to Jupiter, in contradiction to what the article states.
GSwift7
not rated yet Oct 11, 2013
New Horizons actually had escape velocity before the Jupiter flyby. The Jupiter flyby shortened the trip by 2-4 years, but it would have made it anyway. If they had missed the launch window for the Jupiter flyby, they would have gone straight to Pluto. See the third paragraph in the "launch" section of the New Horizon wiki I linked to above for more details.

So, yeah, the article above is WAY off. Not only can the Atlas V-551 go straight to Jupiter, it can go straight out of the solar system, which is much harder.

However, Juno is solar powered, and solar panels are heavy. New Horizons is RTG powered and is only 478 kilograms, compared to 3625 kilograms for Juno. They would have needed to lower the mass of Juno to get it to Jupiter directly, but that doesn't mean we don't have rockets that could do it.

I believe some of the discarded rocket stages from Pioneer and Voyager are also on direct escape trajectories, aren't they?