Kepler Exoplanet Hunter Spacecraft at Risk

By William Harwood /

CBS News/ May 15, 2013, 5:42 PM

Stalled reaction wheel sidelines Kepler spacecraft

An artist's impression showing the Kepler spacecraft studying a distant sun and an exoplanet crossing in front of the star. Kepler finds planets by monitoring how a star's light dims slightly when a planet passes in front as viewed from Earth. / NASA

Updated 5:42 PM ET

NASA's $600 million Kepler Space Telescope, a leading player in the hunt for Earth-like planets orbiting sun-like stars, has been sidelined by problems with stabilizing gyroscopic reaction wheels needed to hold the spacecraft and its 95-megapixel camera precisely on target, NASA managers said Wednesday.

One of Kepler's four reaction wheels was shut down last July and problems with a second wheel -- No. 4 -- were discovered Tuesday when engineers found the spacecraft had put itself into a protective "safe mode" after running into a problem of some sort. Subsequent commands to spin up the No. 4 wheel were not successful.

While the space telescope is equipped with rocket thrusters for major maneuvers, at least three reaction wheels are needed to precisely orient the spacecraft and keep it accurately aimed at its target starfield.

More - Link >>> http://www.cbsnews.com/8301-205_162-57584701/stalled-reaction-wheel-sidelines-kepler-spacecraft/

Source: CBS News.

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