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More than 13 months after its launch, NASA's New
Horizons spacecraft has made its closest pass to
Jupiter on its 10-year voyage to Pluto. The head
of NASA's science directorate and chief
investigator for the mission, Alan Stern, says
the flyby has been eagerly awaited.
"Between the demise of Galileo with the end of
its very successful mission in 2003 and the
arrival of the Juno Jupiter orbiter that we are
all looking forward to in 2016, this is the only
train going this way," said Alan Stern.
New Horizons has been taking pictures of Jupiter
since January and will continue to dispatch them
through June, but the close pass more than two
million kilometers away is giving astronomers
another detailed look at the gas giant, its
rings, and its four biggest moons.
A mission scientist from the Southwest Research
Institute in Boulder, Colorado, John Spencer,
spoke of the goals before Wednesday's Jupiter
pass.
"We very carefully tailored our observations so
we will be not repeating things that have have
been done by the other seven missions that have
already been to Jupiter," said John Spencer.
"Sometimes we are just looking for changes."
The observations have included Jupiter's auroras
and its giant red spot, a swirling centuries-old
storm larger than Earth. New Horizons' advanced
instruments have also peered at the planet's
rings in an effort to find more tiny moons. In
addition, it studied the surface composition of
the big moons Gannymede; Callisto; Io, which has
a volcano; and Europa, which is thought to have
a liquid water ocean under a shell of ice.
The spacecraft will also become the first to
take a trip down the long tail of Jupiter's
magnetosphere, a wide stream of charged
particles extending tens of millions of
kilometers.
Alan Stern says the observations are intended as
practice for the duties New Horizons faces at
Pluto when it arrives in 2015.
"We have designed this particular flyby to be a
stress test on our spacecraft to work out the
kinks so that at Pluto, we do not learn a thing
about our spacecraft, we have worked out those
kinks at Jupiter, putting our spacecraft through
700 different observations," he said.
These observations are only one reason for the
visit to Jupiter. The pass also lets the
planet's strong gravity sling it away, providing
a 14,000 - kilometer per hour speed boost. This
cuts the spacecraft's flight time to Pluto by
three years.
After the Jupiter encounter, New Horizons'
electronics will become dormant for much of its
cruise. Mission controllers will shut off all
but the most critical systems and check in once
a year to test those systems, calibrate
instruments, and correct the course if needed.
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