June 10, 2009
NASA's Wide-field Infrared Survey Explorer (WISE) is undergoing final preparations for a planned November 1 launch from Vandenberg Air Force Base, California.
The mission will survey the entire sky at infrared wavelengths, creating a cosmic clearinghouse of hundreds of millions of objects — everything from the most luminous galaxies, to the nearest stars, to dark and potentially hazardous asteroids. The survey will be the most detailed to date in infrared light, with a sensitivity hundreds of times better than that of its predecessor, the Infrared Astronomical Satellite.
"Most of the sky has never been imaged at these infrared wavelengths with this kind of sensitivity," said Edward Wright, the mission's principal investigator at the University of California, Los Angeles (UCLA). "We are sure to find many surprises."
On May 17, the mission's science instrument was delivered to Ball Aerospace & Technologies Corp. in Boulder, Colorado, where it was attached to the spacecraft. The assembled unit was then blasted by sound to simulate the effects of launch. Tests for electronic "noise" in the detectors will be performed next.
The science instrument is a 16-inch (40-centimeter) telescope with four infrared cameras. A cryostat, or cooler, uses frozen hydrogen to chill the sensitive megapixel infrared detectors down to -447° Fahrenheit (-231° Celsius). The telescope was built by Space Dynamics Laboratory in Logan, Utah.
Among WISE's expected finds are hundreds of thousands of asteroids in our solar system's asteroid belt, and hundreds of additional asteroids that come near Earth. Many asteroids have gone undetected because they don't reflect much visible light, but their heat makes them glow in infrared light that WISE can see. By cataloging the objects, the mission will provide better estimates of their sizes, a critical step for assessing the risk associated with those that might impact Earth.
"We know that asteroids occasionally hit Earth, and we'd like to have a better idea of how many there are and their sizes," said Amy Mainzer, the mission's deputy project scientist of NASA's Jet Propulsion Laboratory (JPL), Pasadena, California. "Whether they are dark or shiny, they all emit infrared light. They can't hide from WISE."
The mission is also expected to find the coldest stars — dim orbs called brown dwarfs that are too small to have ignited like our Sun. Brown dwarfs are littered throughout our galaxy, but because they are so cool, they are often too faint to see in visible light. WISE's infrared detectors will pick up the glow of roughly 1,000 brown dwarfs in our galaxy, including the coldest and closest to our solar system. In fact, astronomers say the mission could find a brown dwarf closer to us than the nearest known star, Proxima Centauri, located approximately 4 light-years away.
"We've been learning that brown dwarfs may have planets, so it's possible we'll find the closest planetary systems," said Peter Eisenhardt, the mission's project scientist at JPL. "We should also find many hundreds of brown dwarfs colder than 900° Fahrenheit (480° Celsius), a group that as of now has only nine known members."
In addition, the survey will reveal the universe's most luminous galaxies seen long ago in the dusty throes of their formation, disks of planet-forming material around stars, and other cosmic goodies. The observations will guide other infrared telescopes to the most interesting objects for follow-up studies. For example, NASA's Spitzer Space Telescope, the Herschel observatory just launched by ESA, and NASA's upcoming James Webb Space Telescope will direct their gaze at objects uncovered by WISE.
WISE will lift off from Vandenberg aboard a United Launch Alliance Delta II rocket. It will orbit Earth, mapping the entire sky in six months after a one-month checkout period. Its frozen hydrogen is expected to last several months longer, allowing WISE to map much of the sky a second time and see what has changed.