PASADENA, Calif. — A Jupiter-bound NASA spacecraft successfully fired its engine Thursday for an important maneuver intended to bring it back toward Earth.
The engine burn was the first of two planned to set up Juno to use Earth's gravity to accelerate it toward the outer solar system. The second engine firing will take place next week.
Launched last year, Juno is zooming toward an encounter with Jupiter in 2016. More than half a dozen spacecraft have visited the solar system's largest planet since the 1970s, but Juno promises to venture closer for a deeper study into Jupiter's evolution. By peering through Jupiter's dense clouds and mapping its magnetic and gravity fields, scientists hope to better understand how the solar system formed.
The $1.1 billion mission is managed by NASA's Jet Propulsion Laboratory.
Juno is 300 million miles from Earth. Since the rocket that carried it was not powerful enough to boost it directly to its destination, it has to cruise out to space and swing back next year to use the Earth as a slingshot to push it toward Jupiter.
The back-to-back burns are needed to put Juno on course to fly by Earth at an altitude of some 300 miles.
Once in orbit, Juno will circle Jupiter's poles 33 times, tracking the amount of water and oxygen in its atmosphere, and determining whether its core is solid or gaseous.
Juno is the first solar-powered spacecraft to venture so far from the sun. It is equipped with three solar panels, each the size of a semitrailer truck.
Juno is designed to study Jupiter for a year and then deliberately crash into the planet so it doesn't pose a threat of biological contamination to moons such as Europa, which scientists think may have a liquid ocean beneath its surface.
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