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In Roman mythology, which is of course is rooted from Greek mythology, Juno was the wife and sister goddess
of Jupiter, and Jupiter was sort of being naughty with some friends so he cast a veil of clouds around
himself and his friends. But of course Juno was a fairly powerful god herself and used her powers to look
right through the clouds and see the true nature of Jupiter and understand what he was really up to. And
that’s exactly what the Juno spacecraft does for us, is that it goes there with special instruments and a
special orbit and uses its powers to see right through Jupiter’s clouds and understand its true nature, which
is holding these secrets for us about how the solar system formed and where we all came from. Juno spins
like a propeller, where the propellers kind of facing the sun because they’re all solar powered. If you spin
something, they stay spinning. It’s like a gyroscope. We can use a spinning spacecraft to let each
instrument get its turn to see Jupiter. We get to go very close to the planet, inside the radiation belts
instead of outside the radiation belts. We’re in a polar orbit so by small adjustments of the timing we can
map the entire planet; we can get repeated stripes at different longitudes as Jupiter spins underneath us.
It does mean that Juno is going to see the polar regions to a greater extent than with other spacecraft, but
I think the most important thing is that it gets in very close to the planet as part of that ellipse. Brings
it in a few thousand miles above those cloud tops, very close near the equator. We’re going to go over the
poles of Jupiter. That means we can study the magnetosphere in a different way. A magnetosphere is the
sphere of influence of the magnetic field. So a planet that has a magnetic field has a magnetosphere when
its sphere of influence extends beyond the planet out into space and affects the region around it. The
magnetosphere of Jupiter is vast. So if you think of Jupiter being ten times the size of the Earth and the
magnetosphere is a hundred times the size of Jupiter. I would expect Juno to tell us more about how planets
work, meaning how the heat gets out, what kind of flows exist inside the body, how magnetic fields get
generated, learning what Jupiter is made of. We will learn such a wide range of things. For indeed, Jupiter
is the most massive planet in the solar system. It is the body you you want to understand in order to
understand the architecture of everything else, including Earth.
NASA Jet Propulsion Laboratory, California Institute of Technology