Page last updated at 19:24 GMT, Monday, 14 December 2009

Nasa sky survey probe blasts off


US sky survey probe launches

A Nasa satellite designed to uncover hidden cosmic objects has blasted off from California.

The Wide-field Infrared Survey Explorer (Wise) blasted off from Vandenberg Air Force Base on a Delta II rocket just after 1409 GMT.

It will pick up the glow of hundreds of millions of astronomical bodies.

The probe is expected to uncover objects that have never seen before, including some of the coolest stars and the most luminous galaxies.

The $320m mission will do this by scanning the entire sky in infrared light with a sensitivity hundreds of times greater than ever before.

Viewing the sky with "infrared glasses" can lift a veil on many objects that are not visible to the naked eye.

Now we're ready to see the infrared glow from hundreds of thousands of asteroids, and hundreds of millions of stars and galaxies
Ned Wright, UCLA

"All systems are looking good, and we are on our way to seeing the entire infrared sky better than ever before," said William Irace, the mission's project manager at Nasa's Jet Propulsion Laboratory (JPL) in California.

The satellite will also have a role in planetary protection: Wise will be able to detect some of the darkest near-Earth asteroids and comets.

This would help efforts to determine whether any of these objects could strike Earth in the near future.

Engineers acquired a signal from the spacecraft just 10 seconds after the spacecraft separated from the rocket.

Approximately three minutes later, Wise reorientated itself with its solar panels facing the Sun to generate its own power.

Super cool

Wise is cooled by a chamber of super-cold hydrogen. Because the instrument sees the infrared, or heat, signatures of objects, it must be kept at chilly temperatures. Its coldest detectors operate below -266C.

"Wise needs to be colder than the objects it's observing," said Ned Wright of the University of California, Los Angeles (UCLA), the mission's principal investigator. "Now we're ready to see the infrared glow from hundreds of thousands of asteroids, and hundreds of millions of stars and galaxies."

Artist's impression of Wise (Nasa)
Wise will cast a wide net for astronomical objects of interest

With the spacecraft stable, cold and communicating with mission controllers, a month-long process of check-out and calibration is underway.

Wise joins two other infrared missions in space: Nasa's Spitzer Space Telescope and the European Space Agency's Herschel Space Observatory.

This mission is different from those others in that it will survey the entire sky.

It is designed to cast a wide net to catch a variety of objects of interest.

Wise will target dim objects called brown dwarfs. These are effectively failed stars, which have not gathered up enough mass to ignite.

Brown dwarfs are cool and faint, and nearly impossible to see in visible light. Mission scientists expect the spacecraft to uncover many hundreds.

This could double or triple the number of star-like objects known within 25 light-years of Earth.

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