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Emily LakdawallaOctober 9, 2013

Juno is in safe mode, but okay and on course following Earth flyby

Following its Earth flyby earlier today, Juno is in safe mode. This is the protective state a spacecraft goes into when it detects a problem. But everything is okay.

For more details, I just spoke with Rick Nybakken, Juno Project Manager at the Jet Propulsion Laboratory. For a bit of background: as Juno flew past Earth, it spent some time in Earth's shadow, that is, "in eclipse." Nybakken told me that Juno entered eclipse in a nominal state, and came out of eclipse in safe mode. He said they have established communications with the vehicle, and that they have full commandability, and that they are in a safe, stable state. They don't know what caused the safe mode yet; they have to analyze the telemetry further.

The gravity-assist flyby was a totally passive event in terms of propulsion for the spacecraft, so the safe mode has no effect whatsoever on Juno's planned trajectory; it's on its way to Jupiter. Nybakken told me they hit the target within 2 kilometers.

I asked him if he knows if the planned Earth imaging took place. He said they don't know yet, as they're still analyzing the telemetry they're getting from the spacecraft; he said he hoped they'd know tonight or early tomorrow morning.

I will update you all as I learn more. Safe modes during gravity assists are not unheard of -- because it's a passive event, they don't disable fault protection as they would for, say, an orbit insertion burn. And a gravity assist flyby is a highly unusual event for a spacecraft. It'd be nice if it hadn't happened, but not a great concern that it did, and Nybakken sounded calm.


NASA / JPL-Caltech

Launched from Earth in 2011, the Juno spacecraft will arrive at Jupiter in 2016 to study the giant planet from an elliptical, polar orbit. Juno will repeatedly dive between the planet and its intense belts of charged particle radiation, coming only 5,000 kilometers from the cloud tops at closest approach.

Read more: mission status, Juno

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Emily Lakdawalla

Solar System Specialist for The Planetary Society
Read more articles by Emily Lakdawalla

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