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Beyond Pluto, NASA craft keeps on trekking

Drawing of Voyager I, the farthest man-made object in space
Drawing of Voyager I, the farthest man-made object in space  

By Richard Stenger

(CNN) -- The most distant spacecraft in the solar system should trek beyond the planets for years to come, thanks to some post-warranty maintenance work of engineers on Earth.

Looking after the Voyager I spacecraft is hardly easy. The 25-year-old probe is more than 7.8 billion miles (12.5 billion km) away.

Yet flight controllers managed to change out some critical components with radio commands that took nearly 12 hours to reach their robotic charge, NASA said this month.

The Voyager team activated a spare sun sensor and star tracker, designed to help the craft determine and plot its position.

"After sitting on the shelf for 15 years, it's like new equipment," said Ed Massey, a Voyager scientist at NASA's Jet Propulsion Laboratory in Pasadena, California.

Voyager I was launched in 1977 to study and photograph the giant planets in the outer solar system. The robot ship survived much longer than their intended four years.

Since swinging by the last of the jovian worlds more than ten years ago, the probe has switched its scientific focus. NASA hopes to use Voyager data learn more about the physical conditions of space and matter at the outskirts of the solar system and beyond.

Barring hardware failure, it boasts enough power and communications capability to keep pushing the frontiers of space and radioing back for at least another 20 years.

The craft is heading toward the boundary of the solar system, known as the heliopause, where the influence of the solar wind gives way to interstellar space. Scientists speculate that it could reach the heliopause within the decade.

To give an idea about its speed, Voyager I could streak from New York to Los Angeles in less than four minutes. Each year, it travels about 3.6 Astronomical Units or AUs. An AU is 93 million miles (150 million km), the distance between Earth and sun.

A robotic twin of Voyager I left Earth in 1975 as well. Voyager II is heading in the opposite direction of Voyager I and traveling at a slightly slower speed.




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