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WMAP finishes nine-year probe of infant universe

Posted: October 6, 2010

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The WMAP satellite devoted to studying the genesis of the universe has finished nine years of observations, but NASA will continue funding the mission for two more years so researchers can extract every bit of science from its ground-breaking observations.

Artist's concept of WMAP in space. Credit: NASA/WMAP science team
Launched in June 2001, the Wilkinson Microwave Anisotropy Probe collected its last science data Aug. 20 and fired thrusters Sept. 8 to leave its operational orbit.

WMAP was stationed about 930,000 miles from Earth at the L2 point, a gravitationally stable location where the tug of Earth's gravity keeps a spacecraft in lockstep with the planet as it orbits the sun. The L2 point is located on the side of Earth opposite the sun.

The spacecraft is now in a permanent parking orbit around the sun, according to a NASA statement releaesd Wednesday.

"We launched this mission in 2001, accomplished far more than our initial science objectives, and now the time has come for a responsible conclusion to the satellite's operations," said Charles Bennett, WMAP's principal investigator at Johns Hopkins University.

The spinning WMAP satellite scanned the sky to measure tiny variations in the temperature of the cosmic microwave background radiation 380,000 years after the Big Bang. Scientists consider the CMB the first light from the young universe after matter and light could exist independently as the universe cooled.

Only sensitive microwave space telescopes can detect the temperature fluctuations, which amount to just a millionth of a degree against an average backdrop of less than -450 degrees Fahrenheit. The measurements reveal warm and cool pockets in the infant universe, the distribution of energy before galaxies and stars began forming.

Among WMAP's accomplishments are the most accurate determination of the age of the universe at 13.75 billion years old, plus or minus 1 percent.

And WMAP confirmed normal atomic matter only makes up 4.6 percent of the material in the known universe. Dark matter, which has not been detected yet, makes up another 23 percent of the universe, while exotic dark energy comprises the remaining 72 percent.

The mission's ultimate legacy is still being written.

A mosaic of the first seven years of WMAP observations showing small fluctuations in the cosmic microwave background temperature. Credit: NASA/WMAP science team
The science team will be on the job through 2012 analyzing the final two years of data gathered by WMAP. Only the first seven years of results have been processed so far.

"WMAP has opened a window into the earliest universe that we could scarcely imagine a generation ago," said Gary Hinshaw, the mission manager at NASA's Goddard Space Flight Center. "The team is still busy analyzing the complete nine-year set of data, which the scientific community eagerly awaits."

NASA approved the two-year post-operations phase after a panel of senior independent researchers recommended funding further processing of raw WMAP data and its public release.

"WMAP gave definitive measurements of the fundamental parameters of the universe," said Jaya Bapayee, WMAP program executive at NASA Headquarters. "Scientists will use this information for years to come in their quest to better understand the universe."

A European Space Agency mission named Planck carries instruments covering a frequency range 10 times greater than WMAP. Planck launched in 2009 finished the first of four planned sky surveys earlier this year.

Scientists say WMAP's measurements complement Planck and will continue to be useful in the future.