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SYFY WIRE Bad Astronomy

Jupiter Looms Ahead for Juno

By Phil Plait

On July 5, at 03:18 UTC (July 4 at 11:18 p.m. Eastern U.S. time), the Juno spacecraft will ignite its main engine. It will burn for 35 minutes, and when it’s done, the spacecraft will be doing something a NASA mission hasn’t done in many years: It will be orbiting mighty Jupiter, the biggest planet in the solar system.

Oh my, yes, this is a big deal.

Juno’s mission is to investigate Jupiter, observing its dynamic atmosphere to determine its composition, temperature, and cloud structure. It will measure Jupiter’s ridiculously powerful magnetic and gravitational fields, and reveal what the interior of the giant planet is like. The overarching goal: Find out how Jupiter formed, and how it’s changed in the billions of years since then.

It’ll do this with a fleet of scientific instruments, including particle detectors, a magnetometer, cameras, and many others (SpaceFlight 101 has a great overview of all of them). One instrument, JunoCam, is designed to take color pictures of Jupiter, including its poles, which have never been seen before from above. I was amazed to find out that when Juno is closest to Jupiter (called perijove), JunoCam will have a resolution of 15 kilometers per pixel! Mind you, Jupiter is a staggering 140,000 km across, so we’re talking very high detail shots. We’ll get stunning views of Jupiter’s atmosphere and, hopefully, its aurorae. Emily Lakdawalla has a great write-up of JunoCam on her blog at the Planetary Society.

Before you ask, no, it won’t be getting any pictures of Jupiter’s moons to my knowledge. They’re not the focus of the mission, and besides they’re small and will be far away, so they wouldn’t look like much anyway.

This is an ambitious mission, made even more difficult by Jupiter’s radiation belt. Jupiter has an incredibly powerful magnetic field, and that’s trapped subatomic particles from the solar wind and emitted from its moon Io. These particles are accelerated to high energy and can damage spacecraft components. Juno’s hardware is hardened against this, but even so it limits the lifetime of the mission. The design is to last for 36 orbits of Jupiter; after that it is planned to do a deorbit burn and fall into the planet itself in 2018.

We’ve sent spacecraft to Jupiter many times, but with one exception they’ve all been flybys, brief but amazing. The exception was Galileo, which orbited Jupiter but suffered a hardware problem with its main antenna that prevented rapid downloading of its data, limiting the goals of the mission. It still worked, and did amazing science, though.

Another pretty cool thing is that the Juno spacecraft is powered by solar panels, which is something that until recently hadn’t been possible for outer planets. Sunlight is weaker out there, and it wasn’t until this mission that solar panels were efficient enough to power a spacecraft; on top of that the instruments are also very efficient with their power, allowing lower energy generation needs.

But why believe me? Here’s my pal Bill Nye to explain it:

I’ll be watching the Jupiter Orbital Insertion live and tweeting it. Emily Lakdawalla will as well, and she has a timeline of insertion events on her blog worth keeping bookmarked, too.

It’s been a while since we’ve seen Jupiter up close. This should really be amazing.

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