Jupiter, the largest planet in the solar system, is about to welcome
a robotic visitor.
NASA's New
Horizons probe will make its closest pass by the gas giant at about 12:45
a.m. EST (0545 GMT) Wednesday in a sort of cosmic stopover on its long trek to distant
Pluto and the Kuiper
Belt. The planetary
flyby comes just 13 months after New
Horizons' launch, with the probe hurtling through space at about 47,000
miles per hour (75,639 kph) on what NASA
is billing as its fastest mission to solar system's edge.
"We have a
very narrow window in space that we have to hit," New Horizons principal
investigator Alan
Stern, of the Southwest Research Institute (SwRI) in Boulder, Colorado, has
said of the rendezvous. "It's about 500 miles (804 kilometers) across and we
have to hit it from 500 million miles (804 million kilometers) away, from the Earth."
It's the
equivalent of shooting a skeet target in Baltimore, Maryland from a firing
range in Washington, said Stern [VIDEO:
Follow the Jupiter flyby].
At
its closest approach, the New Horizons is expected to fly within 1.4 million miles (2.3 million
kilometers) of Jupiter. The first data from that pass is expected to arrive at
Earth via the Deep Space Network at around 12:00 p.m. EST (1700 GMT) Wednesday,
officials at the Johns Hopkins University's Applied Physics Laboratory (JHUAPL),
which is overseeing the mission for NASA, told SPACE.com [VIDEO:
Passport to Pluto].
New
Horizons is the first probe to visit Jupiter since NASA's Galileo
orbiter plunged
into the gas giant's atmosphere to end its 14-year
mission in 2003. The Cassini orbiter,
currently circling the planet Saturn,
swung
past Jupiter in December 2000.
New
science awaits
Already,
the New Horizons probe has returned new views [image
1, image
2] and movies of Jupiter's moons [view
movie], though the interaction of the Sun's
solar wind with the planet's vast
magnetosphere takes center stage for some researchers.
Jupiter has
the largest magnetosphere in the solar
system, with its trailing non-Sunward direction - known as the magnetotail [image]
- stretching out towards the orbit of Saturn. New Horizons instruments have
already detected a dense region of solar
wind known as a shock, which develop as a fast layer of solar wind
particles compress a slower layer ahead like a snow plow.
"I think
the most exciting part about the next few days is that we'll see our closest
measurements to Jupiter," SwRI's David McComas, principal investigator for New
Horizon's Solar Wind Around at Pluto (SWAP) instrument, told SPACE.com.
New Horizons'
observations of Jupiter's magnetic field will help researchers determine which
processes - such as solar wind or planetary rotation - spawn auroras and other phenomena. The
results will be compared tandem studies by the Hubble Space Telescope and
other space and ground-based observatories, McComas said.
The
Pluto-bound probe will also be the first spacecraft ever to fly down Jupiter's
magnetotail, a journey that could take anywhere between 45 and 70 days
depending on how the magnetic field "flaps" as it extends from the gas giant
planet, researchers said.
"It's sort
of like a windsock...because the solar wind doesn't flow exactly radially outward,"
McComas said of the magnetotail, which may extend anywhere between 1,000 and
1,500 times the radius of Jupiter. The planet's radius spans about 43,495 miles
(70,000 kilometers).
Spacecraft
shakedown
New
Horizons' Jovian magnetosphere studies are part of no less than 700 separate
observations planned during the Jupiter flyby, which serves as a shakedown
period for the spacecraft's seven instruments. The probe will also grab a
gravitational boost from the planetary pass, shaving three years off its journey
for a July 2015 Pluto rendezvous [image].
"Here
on the ground we aren't yet seeing much science data, but the engineering data
we're getting shows the encounter is progressing nominally and the various
observations are coming off right on schedule," Stern wrote in Monday status
update on the New Horizons mission website at JHUAPL.
New
Horizons began studying Jupiter and its moons in earnest on Feb. 24, and is conducting
between 15 and 20 observations each day, Stern said. On Monday, the spacecraft
was due to map the surfaces of Jovian moons Ganymede
and Europa,
study the atmospheres of satellites Io
and Callisto,
as well as photograph Jupiter's
"Little Red Spot," Io's volcanic
plumes and the gas giant planet's faint rings, he added.
It
takes about 45 minutes for a signal from New Horizons to reach Earth from Jupiter's
neighborhood, according to a mission description.
Much
of New Horizons' Jupiter flyby instructions have already been uploaded to the spacecraft
since the probe will be out of contact with Earth while it studies the Jovian
system.
Those
instructions include an auto shutdown of the SWAP instrument in case Jupiter's
near magnetosphere proves too strong for the tool, which was designed primarily
for the Pluto environment, McComas said. If that occurs, SWAP should restart
automatically once New shortly after Horizons' closest swing past Jupiter, he
added.
"You work
on these things for many years, designing and developing, going through a
launch and getting the thing up in space," McComas said. "It's an extremely
exciting time for my team and me."
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