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Jupiter-bound probe to snag speed boost from Earth

Juno, a NASA spacecraft en route to Jupiter, will pass Earth on Wednesday, picking up a gravity speed boost that will help fling it out toward the gas giant. 

By Douglas / October 9, 2013

The Juno spacecraft will fly past the Earth on Wednesday.



A NASA spacecraft bound for Jupiter will buzz Earth Wednesday (Oct. 9) to snag a gravity speed boost that will slingshot it toward the largest planet in the solar system.

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The Juno spacecraft will be within 350 miles (560 kilometers) of Earth when it zooms by our planet at 3:21 p.m. EDT (1921 GMT). It will be passing over South Africa during its closest approach to Earth.

Since its 2011 launch on an unmanned Atlas 5 rocket, NASA's Juno mission to Jupiter has followed a circuitous route toward Jupiter. This pass around Earth will give it the boost it needs to make it the rest of the way to the solar system's largest planet, accelerating the spacecraft from its current speed —78,000 mph (126,000 km/h) with respect to the sun — to a speed of 87,000 mph (140,000 km/h). [See photos of NASA's Juno mission to Jupiter]

"Juno is a large, massive spacecraft," Juno mission principal investigator Scott Bolton with the Southwest Research Institute in San Antonio, Texas, said in a statement. "Even a large rocket couldn't provide enough propulsion to get us all the way to Jupiter, so we are flying by the Earth for a gravity-assist that will provide about 70 percent of the initial boost provided by the Atlas V 551 rocket. The gravity assist essentially provides as much propulsion as a second rocket launch."

SwRI officials released a video of the Juno probe's Earth flyby to describe how the spacecraft will use Earth's gravity to help it reach Jupiter.

Although 97 percent of NASA staff members are furloughed due to the government shutdown, Juno's mission-critical Earth flyby operations have not been affected.

The 8,000-pound (3,267 kilograms) Juno probe is the first solar-powered spacecraft to explore the outer solar system, and has three large solar arrays, each of which is the size of a tractor-trailer. It also holds a titanium vault to protect sensitive electronic equipment from the harsh environment around Jupiter.

"While we are primarily using Earth as a means to get us to Jupiter, the flight team is also going to check and calibrate Juno's science instruments," Bolton said in the statement.

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