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February
26, 2007: When New Horizons, NASA's Pluto-bound spacecraft,
swings by Jupiter on Feb. 28th, it will pick up a few souvenirs
along the way – photos, data, and an extra 9000 miles per
hour courtesy of the largest planet in our solar system.
New
Horizons is already the fastest spacecraft ever to leave Earth,
but it needs even more speed to catch Pluto, which is receding
from the sun. Winter is coming to Pluto, and researchers want
New Horizons to arrive before Pluto's thin atmosphere freezes
and falls to the ground. (It's so much easier to study an
atmosphere when it's up in the air.)
 So
New Horizons is going to steal a little energy from Jupiter.
"It's
called a gravity assist maneuver," says Dr. Robert Farquhar,
formerly the New Horizons mission director at the Johns Hopkins
University Applied Physics Laboratory. "New Horizons
will dip into the gravity well of Jupiter and 'slingshot out'
with more velocity than it had when it went in." [diagram]
Right:
An artist's concept of the Jupiter flyby. Credit: JHUAPL/SwRI
For
New Horizons to speed up, of course, Jupiter must slow down.
"That's conservation of energy," he says. But no
one will notice. The change in Jupiter's orbit around the
Sun due to the flyby is fantastically small. New Horizons
will absorb about 1/1025 of Jupiter's orbital energy.
That's like "taking a single drop out of the ocean,"
says Farquhar.
(1025
is 1 followed by 25 zeros. Coincidentally, there are about
1025 drops in the combined oceans of Earth, so
Farquhar's analogy is correct.)
This
insignificant loss for Jupiter amounts to a big boost for
New Horizons. The piano-sized spacecraft will gain enough
energy to exceed 52,000 mph – fast enough to reach New York
from Tokyo in less than eight minutes. New Horizons will reach
the Pluto system in July 2015 – five years earlier than without
the Jupiter boost.
Long
before space travel was possible, Farquhar said, astronomers
saw the potential of using gravity to fuel space travel. "We've
known about this since at least the nineteenth century,"
he said.
 Jupiter
is not the only helping hand in the solar system. Earth's
gravity has donated its share of energy to ten different space
vehicles, beginning in 1990. The first was Giotto, a European
Space Agency mission to study Halley's Comet. Giotto launched
in 1985, passed Halley's Comet in 1986, and in 1990 returned
to Earth's orbit, where it picked up a gravity-assist boost
and a redirection toward another comet, Grigg-Skjellerup,
in 1992.
Right:
Click on the image for a gravity assist tutorial from JPL.
[More]
The
most-recent spacecraft to fly by Earth was MESSENGER, NASA's
Mercury-bound spacecraft. Short for "MErcury Surface,
Space ENvironment, GEochemistry, and Ranging," MESSENGER
launched on Aug. 3, 2004 and swung past Earth almost one year
later in 2005. Along the way, it picked up an added boost,
a redirection, and hundreds of stunning images of Earth.
Like
MESSENGER, New Horizons will make the most of its flyby time.
Through June, it will make more than 700 observations. This
includes scans of Jupiter's turbulent, stormy atmosphere;
a detailed survey of its ring system; and a detailed study
of Jupiter's largest moons. The spacecraft also will take
the first-ever trip down the long "tail" of Jupiter's
magnetosphere, a wide stream of charged particles that extends
tens of millions of miles beyond the planet, and the first
close-up look at Red
Spot Jr., a nascent storm south of Jupiter's famous Great
Red Spot.
Later,
after an eight-year cruise from Jupiter, New Horizons will
conduct a five-month-long study of Pluto and its moons. Stay
tuned!
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Authors: Sherrie Super and Dr. Tony Phillips | Editor:
Dr. Tony Phillips | Credit: Science@NASA
| More
Information |
| New
Horizons -- mission home page
NASA
Spacecraft En Route to Pluto Prepares for Jupiter Encounter
-- NASA press release
Credits:
New Horizons is the first mission in NASA's New Frontiers
Program of medium-class spacecraft exploration projects.
The Discovery and New Frontiers Program Office at NASA's
Marshall Space Flight Center manages the New Frontiers
Program for NASA Headquarters. The JHU Applied Physics
Laboratory manages the New Horizons mission for NASA's
Science Mission Directorate. The mission team also includes
NASA's Goddard Space Flight Center, Greenbelt, Md.;
NASA's Jet Propulsion Laboratory, Pasadena, Calif.;
the U.S. Department of Energy, Washington; Southwest
Research Institute, Boulder, Colo.; and several corporations
and university partners.
New
Horizons Animations -- highly recommended!
A
Gravity Assist Primer -- from JPL's classic Basics
of Spaceflight.
NASA's
Future: The
Vision for Space Exploration |
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