BOULDER, Colorado -- Now heading
outward on its lengthy trek to tiny Pluto, NASA's New Horizons spacecraft is on course to zip by gigantic Jupiter early next year.
Engineers
and scientists are plotting out an agenda of at-Jupiter investigations. Thanks
to high-tech instruments onboard the craft, new looks at the gas giant are
slated, as are views of several moons circling the planet.
But
while science at Jupiter is to be gained, the real game is to shakeout New
Horizons long before it encounters the Pluto system in 2015. Earlier this year
the spacecraft photographed both Jupiter, and its final destination, Pluto.
Hit the keyhole
New
Horizons roared into space in January of this year--the first mission to carry
out an initial reconnaissance of Pluto-Charon and the Kuiper Belt at the edge
of our solar system.
"The
first objective at Jupiter is to hit the keyhole to get us to Pluto. If we
don't do that...nothing else matters," said Alan Stern, principal investigator
for New Horizons and executive director of the Space Science and Engineering
Division here at Southwest Research Institute (SwRI).
Hitting
that little window in space is a priority, a predetermined but needed course correction
for New Horizons. The adjustment will place the probe on a trajectory to attain
a closest approach of Pluto some 8 years hence, on July 14, 2015.
Like
a test drive of a new automobile, Stern said that New Horizons zooming by
Jupiter is a full-up practice run. The flyby will show how the probe handles
and help flesh out any unknown issues lurking within the spacecraft--from
software and commands to the science instruments.
Stress test
One
nagging engineering issue has already been flagged.
New
Horizons is using two of its 16 thrusters more than expected, Stern said. "So
we're going to have to limit our appetite and learn to fly the spacecraft a
little bit differently...or we'll use them all up before we get to Pluto."
"Pluto
is a one-shot," Stern told SPACE.com. "I don't fundamentally want things
to go wrong...but I want them to go wrong at Jupiter and not at Pluto. At Pluto,
my first and only objective is to learn about Pluto. If I learn anything at all
about the spacecraft at Pluto...that would not be good."
New
Horizons will take on Jupiter operations for five months, from January to the
end of June next year. But within that timeframe, there are 10 days of very
intense science investigations now being scheduled.
"This
is a stress test. Just like the doctor gets your heart racing on a treadmill...we
are really putting that spacecraft through its paces," Stern added.
New
Horizons is the 8th spacecraft to arrive at the Jupiter system.
"We
are going to do a lot of good science," Stern explained. For one, the probe
will fly down Jupiter's magnetotail-- never before done event.
Due
to the Jupiter's strong magnetic field, the planet's magnetosphere fills a vast
volume of space. As New Horizons departs the Jovian system, the path to Pluto
happens to take the spacecraft down the "tail" of Jupiter's magnetosphere that
is pulled back behind the planet.
Goals at Europa
Jupiter
science targets on the New Horizons to do list include looks at the planet's
little and great red spots, ring structure, as well as Io and Europa--two moons
of Jupiter's entourage of over 60 moons found so far.
"We
have a few goals at Europa," noted John Spencer, a staff scientist at SwRI's
Department of Space Studies and also the New Horizons deputy imaging node
leader. "We'll have a somewhat improved look at the infrared spectrum of the
darker non-ice material on Europa's surface," he told SPACE.com.
That
material seems to be some sort of water-bearing salt or perhaps sulfuric acid -
and may hold clues to the composition of Europa's subsurface ocean, Spencer
pointed out.
Other
goals at Europa are to understand its ultra-thin oxygen atmosphere better,
Spencer added. That will be done by New Horizons obtaining spectra of the
ultraviolet airglow emissions from that moon's atmosphere. Also, the spacecraft
will watch a star pass behind Europa and look for absorption of the starlight
by Europa's atmosphere. A similar tactic is being applied in observing Io's
more substantial atmosphere.
"We'll
also be mapping some very peculiar huge circular grooves on Europa which can
only be seen when the Sun hits the surface at just the right angle," Spencer
said.
Staring at the rings
Spencer
said that the New Horizons science team and associates are looking to do things
that haven't been done before at Jupiter...or inspecting things that are changing
with time.
As
example, infrared scans of ammonia clouds that appear and disappear in the wake
of Jupiter's great red spot are to be done. New Horizons totes a near-infrared
instrument with much higher spectral resolution than equipment carried on the
earlier Galileo mission at Jupiter, he said.
"So
we're focusing on something pretty cool that hasn't been done before," Spencer
said.
In
addition, New Horizons will spend a lot of time staring at the rings, looking
for very small satellites that may be embedded in the rings that haven't been discovered
before, Spencer observed. "There's some interesting structure in the rings that
may be due to dust being shed off smaller bodies."
Volcanic Io: hot, hot, hot
Jupiter's Io - a volcanically active moon studied intently by NASA's Galileo spacecraft as follow-up to earlier Voyager 1 Voyager 2 observations -- is due for scrutiny by New Horizons too.
"We'll
spend a lot of time staring at the night side of Io...looking in the visible and
near-infrared," Spencer said. New Horizons data, he added, should help bracket
the high temperatures for volcanoes on Io.
"Some
observations from Galileo found them embarrassingly hot," Spencer explained.
"Are there really super-heated eruptions on Io...some exotic lava being
erupted...or is it plain old basalt?"
But
to help clear up the mystery, Io will have to cooperate and cough up the goods
on New Horizons time, Spencer said.
There's
much to do in readying both spacecraft and the entire New Horizon team for the
close encounter of the Jovian kind. New Horizons will whisk by Jupiter at
closest approach on February 28, 2007, speeding through space at some 47,000
miles per hour (about 21 kilometers per second).
"Right
now, we wish we had more time. It's a little too fast," Spencer concluded.
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