Engine Concerns Keep Jupiter Spacecraft, Juno, in Slower Orbit
published during a waning crescent moon.
02/21/2017

NASA’s Juno spacecraft, currently in orbit around Jupiter, is staying in a slower orbit after mechanical woes worried engineers. The spacecraft arrived at the gas giant on July 4th, 2016, where it made a 35-minute long burn to slip into its arching elliptical orbit. Every 53.5 days, the spacecraft swoops to just 2,600 miles (4,100 kilometers) over the clouds. The closest approach to the planet lasts just a few hours and is packed with rapid science observations before Juno heads back into space to start the journey over again.

Juno’s mission is deceptively simple: Learn what lurks beneath Jupiter’s dramatic clouds, investigate the origin of gas giants, and describe the planet’s vast and powerful magnetic fields.

Engine Concerns

Jupiter’s “string of pearls” storm sequence captured by Juno on December 11, 2016 from 15,200 miles (24,400 kilometers) away. Credit:  NASA/JPL-Caltech/SwRI/MSSS/Eric Jorgensen

Originally, mission scientists intended for Juno to make just two of these slower orbits before burning the spacecraft’s engines once again, tightening up into a 14-day orbit. But while checking up on the spacecraft’s health after its long interplanetary journey, engineers discovered two helium check valves in the main engine were taking longer to open and close than expected. The malfunction doesn’t impair the spacecraft’s science capacity or endanger its operations, but it does leave mission scientists nervous that any engine burns could be sloppy. Instead of risking Juno ending up in a less-than-optimal orbit, the scientists announced a new plan on February 17th. Juno will stay in its current slower orbit, making just 12 orbits before its funding is considered for extension in July 2018.

Engine Concerns

Juno’s original mission plan involved 2 larger 53-day orbits before tightening up into 14 day orbits. Now, Juno will stay in the larger, slower orbit. Credit: NASA/JPL-Caltech

The change in plans doesn’t necessarily compromise Juno’s science objectives. The current orbits pass the same distance over Jupiter’s poles, so the data collection will be to the same level of detail. Although Juno will be making fewer orbits, it will also be spending less time in Jupiter’s punishingly-intense electromagnetic fields. This may extend the radiation-hardened spacecraft’s lifespan beyond its anticipated mission duration. The new mission format also opens up the opportunity for more science observations farther from Jupiter, exploring the outer reaches of the gas giant’s magnetic field.

Every orbit, the spacecraft points its JunoCam camera at targets selected by the public. Vote on future target selection or download raw image data to process at home.

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