NASA Begins Countdown to Pluto Flyby

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An artist's impression of NASA's New Horizons spacecraft, currently en route to Pluto; after nine years and a journey of 3 billion miles, NASA's New Horizons robotic probe will be woken from hibernation to begin its unprecedented mission: the study of the icy dwarf planet Pluto and its home, the Kuiper Belt. Science@NASA/Reuters

Today marks the beginning of the world's encounter with Pluto, as a NASA spacecraft that has journeyed for nine years begins its first phrase of approach to the dwarf planet.

The spacecraft is still 135 million miles away from Pluto, but Thursday marks a significant day for NASA scientists as the beginning of a series of phases in which the spacecraft can start studying and capturing increasingly detailed images of the Pluto system.

In just under six months, the world will catches its first close-up glimpse of Pluto when NASA's New Horizons zooms within 6,200 miles of the dwarf planet on July 14.

New Horizons has traveled 3 billion miles since its launch on January 19, 2006, according to NASA. That's farther than any other other space exploration mission has ever gone to reach its primary target.

As with space missions before it, the New Horizons spacecraft is packed with interesting memorabilia, including two U.S. flags and some of the ashes of Clyde Tombaugh, the American astronomer who discovered Pluto in 1930.

The spacecraft has spent about two-thirds of the time since its launch (intermittently) "in hibernation" in order to reduce the wear and tear on equipment and minimize the risk of system failures. But on December 6 last year, the spacecraft came out of hibernation and switched into active mode for its final approach.

"This is a watershed event that signals the end of New Horizons crossing of a vast ocean of space to the very frontier of our solar system, and the beginning of the mission's primary objective: the exploration of Pluto and its many moons in 2015," said Alan Stern, the principal investigator for New Horizons, when the spacecraft awoke last month.

In a "PI's Perspective" blog post from New Year's Eve—or Pluto Eve as Stern called it—Stern explained that for the first few weeks after the spacecraft awoke, the team was checking and calibrating the instruments on board, planning and testing flight plans and otherwise preparing the spacecraft for Approach Phase 1 of the Pluto encounter, which began Thursday.

Starting on January 25, the spacecraft will be capturing images of the Pluto system as part of the "optical navigation campaign to make sure the spacecraft is on course," says project scientist and co-investigator Hal Weaver. New Horizons will observe and take photos during one full rotation of Pluto and its largest moon, Charon, around their common center of mass. NASA is expected to produce a movie that culls from those images sometime in February.

Pluto is a dwarf planet, which means that it is round and orbits the sun like the eight major planets, but is much smaller in comparison and has not cleared its orbital path of other objects such as the icy objects of the Kuiper Belt beyond Neptune's orbit.

Though the early images will show Pluto at no more than two pixels across, by mid-May those images will surpass what the Hubble telescope could capture. During Approach Phase 2, which begins on April 5, the team will be collecting data specifically meant for science rather than focusing primarily on navigation. On June 23, the start of the third and final approach phase, they will "really ramp up on the cadence of what we're doing and the quality of what we're doing," says Weaver.

The three main goals of the "closest approach" in July, says Weaver, are to map the surface of Pluto with great detail, measure its composition and probe its atmosphere.

Besides the seven instruments performing various scientific tasks on New Horizons, there's a short list of other items along for the ride, or "nine mementos on their way to the ninth planet," a NASA spokesman says.

A portion of the ashes of Tombaugh, who died in 1997, are in a container attached to the bottom of the spacecraft. The inscription on the container reads:

Interned herein are remains of American Clyde W. Tombaugh, discoverer of Pluto and the solar system's 'third zone' Adelle and Muron's boy, Patricia's husband, Annette and Alden's father, astronomer, teacher, punster, and friend: Clyde W. Tombaugh (1906-1997).

Tombaugh's ashes are not the fist to have traveled on a NASA craft. In 1999, a vial of geologist and outer space collisions expert Eugene Shoemaker's ashes hit the moon while on NASA's Lunar Prospector.

Other items onboard New Horizons include state quarters from Maryland and Florida, where the ship was built and launched, respectively; a CD-ROM containing the names of more than 400,000 people who wanted to be part of the exploration and another containing photographs of the project personnel; two U.S. flags; a piece of SpaceShip One; and a 29-cent U.S. postage stamp from 1991 that says "Pluto: Not Yet Explored."

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A small container of Clyde Tombaugh’s ashes is affixed to the inside, upper deck of the New Horizons spacecraft. JHU-APL/NASA
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As this U.S. postage stamp from 1991 flies past Pluto aboard NASA's New Horizons, its message will become obsolete. JHU-APL/NASA