NASA Mission to Explore Solar System's Edge
By WARREN E. LEARY
Published: January 15, 2006
For more than four decades, humans have been sending out spacecraft to explore the known planets of the solar system. At long last, it is time to visit the last planet.
On Tuesday, a powerful Lockheed Martin Atlas 5 rocket is scheduled to send a spacecraft called New Horizons on a journey to the dim outer reaches of the Sun's realm for the first close-up look at Pluto. If successful, the mission will complete the initial exploration of the nine planets that defined the solar system at the beginning of the space age.
The three-stage Atlas will hurl the spacecraft away from Earth at a record 36,000 miles per hour, fast enough to pass the Moon in nine hours - compared with two and a half days for an Apollo mission - so that it can reach Jupiter in just 13 months. A gravity assist from the giant planet, which also will serve as a test bed for New Horizons' seven instruments, is to speed the craft on to Pluto.
Once near its target, in 2015, the spacecraft is to conduct about five months of studies, including a dash that takes it within 6,200 miles of Pluto's surface and 16,800 miles from the planet's large moon, Charon. In addition, mission scientists said, it will study two smaller moons, found late last year by the Hubble Space Telescope, and any new features discovered in transit.
Even with a fast start, the three-billion-mile journey to Pluto will take at least nine and a half years, and the compact robot craft will have to conserve energy. So for most of the flight, it will be in a state of hibernation, sending a brief weekly signal back to Earth to report its condition and being awakened by mission control only once a year for an instrument check....
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