SwRI (Dan Durda)/JHUAPL(Ken Moscati)
In this artist's rendering, New Horizons is just past its closest approach to the planet, on Feb. 28, 2007. Near the sun are Earth, Venus and Mercury.
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updated 12/16/2010 6:39:33 PM ET 2010-12-16T23:39:33

A NASA Pluto probe may be slumbering at the moment, but it's still tearing through space at a blistering pace, closing in on the orbit of Uranus.

The New Horizons probe is the fastest spacecraft ever launched from Earth, having sped from its home planet in 2006 at about 36,000 mph (nearly 58,000 kph). It had covered half the distance of its nearly 3 billion-mile (4.8 billion-kilometers) voyage by last February, and the spacecraft should reach Pluto in July 2015.

Currently, New Horizons is about 18.5 times farther from the sun than the Earth is, and it should pass the orbit of Uranus in March 2011, NASA officials said.

Guided by recent Pluto revelations
The spacecraft is flying to study Pluto and its three known moons Nix, Hydra and Charon. In recent years, a number of revelations have come out regarding Pluto from the Hubble Space Telescope, such as the discovery of Nix and Hydra, as well as apparent geyser eruptions and seasonal color changes on the dwarf planet.

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"These discoveries have helped develop our encounter with Pluto, which is now fully planned," said New Horizons principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colo. "We have a list of things of do, which has been converted into a timeline of events, which has been converted into spacecraft software with all the commands to run the spacecraft and instruments."

New Horizons "is very different from most missions in the solar system today," Stern told SPACE.com. "It's like we're back at the early days of planetary exploration."

Dozens of missions have been sent to Mars and the moon, and multiple spacecraft have checked out Venus, Jupiter, Mercury and Saturn, as well as various comets and asteroids. But faraway Pluto has escaped such attention thus far, Stern said, as has its neighborhood, the Kuiper Belt the ring of icy bodies beyond Neptune's orbit.

Shedding light on dark, cold worlds
"With New Horizons, this is our first reconnaissance of Pluto, of this kind of world we've never sent a mission to the dwarf planets before, never sent a mission to the Kuiper Belt," Stern said. "This is the first time we're going to see a new type of planet since the '70s, when we had our first mission to a giant planet, Jupiter."

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Pluto and the Kuiper Belt remain mysterious in many ways, and New Horizons should help fill in some major gaps, Stern said.

"So we don't have a narrow scope here we're going to write the book on Pluto and the dwarf planets," he said. "We're here to map Pluto, map its surface composition, measure its atmospheric composition, pressure and temperature and assay the same kinds of measurements for all of its satellites."

Pluto was demoted from full-fledged planet to a newly created category, "dwarf planet," in 2006. Stern doesn't disagree with the "dwarf" designation, but he has argued that stripping Pluto of its planethood was wrong and unscientific. [ Fighting for Pluto's Planet Title: Q & A with Alan Stern ]

Probe sleeping, for now
New Horizons is hibernating now, as it does for most of the year. It wakes up for about two months each summer to test its systems, calibrate its instruments and gather tracking data needed to make course corrections as necessary, Stern said.

The spacecraft also rouses itself for about 10 days in both November and January to do more tracking and maintenance activities. So far, everything has checked out fine.

"New Horizons is healthy," Stern said. "All systems and instruments are working well, and we have never had a case where we've had to use a backup system owing to a problem. We have good fuel reserves, too, and we're bang on course to Pluto."

After it reaches Pluto, New Horizons will not stop its flight to orbit the dwarf planet. Instead, after its flyby, it will dash out into the Kuiper Belt to investigate the icy bodies lurking in that mysterious realm. The New Horizons team has not yet chosen which Kuiper Belt object they might visit after Pluto.

The search for candidates will start next year, Stern said. Scientists will use giant Earth-based telescopes to pick out flyby targets beyond Pluto, to be reached in the late 2010s and early 2020s.

"I want to know as much about what candidates are out there and as much about the candidates as possible before making the best possible decision," Stern said. "Making a decision too early would be like picking fruit that's not ripe yet."

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Gallery: The new solar system

Get the facts about dwarfs, giants, terrestrials and other denizens of our planetary realm.

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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