NASA’s Sky-Mapping Spacecraft To Launch in December
WASHINGTON — Despite budget cuts and programmatic changes that delayed its launch more than a year, NASA’s new asteroid-hunting space telescope rolled out to the pad at Vandenberg Air Force Base, Calif., Nov. 20 in preparation for launch atop a 2 rocket no earlier than Dec. 9.
Known as the Wide-field Infrared Survey Explorer (WISE), the spacecraft will spend the next 10 months circling the Earth over the poles and scanning the complete sky at infrared wavelengths to uncover hidden cosmic objects, including cool stars, dark asteroids and luminous galaxies.
“You can kind of think of it as the Google Map of the universe,” said Amy Mainzer, NASA’s deputy project scientist for WISE, explaining that the instrument will take repeated exposures of the same swath of sky, creating overlapping images as the telescope progresses through its sky scan. The stars and galaxies will appear fixed in the sky in each exposure, but asteroids will move over short amounts of time.
“WISE is going to be finding about 100,000 new asteroids in the main asteroid belt,” Mainzer said during a Nov. 17 news conference at NASA headquarters here. “And we expect it’s going to find several hundred new asteroids that get close to Earth orbits.”
The $320 million project, managed by NASA’s Jet Propulsion Laboratory in Pasadena, Calif., was competitively selected under NASA’s Explorers Program, managed by the agency’s Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah, and the spacecraft was built by Boulder, Colo.-based Ball Aerospace & Technologies Corp.
WISE principal investigator Edward “Ned” Wright of the University of Southern California in Los Angeles, said the instrument will provide a vast improvement over past infrared sky surveys.
“We will find millions of objects that have never been seen before,” he said during the news conference.
NASA selected the WISE mission in 2002 for further study, but waited until 2004 to proceed with the project. At that time, NASA expected the mission to cost $208 million. But more budget-driven delays and a NASA mandate to launch the spacecraft on a Delta 2 rather than a smaller, less expensive Orbital Sciences’ Taurus rocket caused project costs to increase, Wright said.
“NASA directed us to use a Delta launch vehicle, which is a very, very experienced line of launch vehicles, so we’re not unhappy with that, but it does cost more than what we proposed for, which was the Taurus,” Wright said.
NASA also decided in late 2005 to keep WISE in formulation an additional year, a cost-cutting effort that delayed the project’s launch readiness date from 2008 to mid-2009. Finally, in late 2006, NASA gave the WISE team the green light to proceed toward an October 2009 launch date.
“NASA has a fixed budget, and everything that NASA wants to do — and there are many things that NASA wants to do — all take part of that budget,” Wright said following the Nov. 17 prelaunch press conference. “Basically, because of budget problems, our funding was cut so we had to slow down. So it takes longer, and it takes more money.”
WISE project manager William Irace said that since NASA confirmed the WISE mission in October 2006, the project has experienced only 1 percent cost growth.
“Once that was settled on — when they wanted us to build it, when they wanted us to launch it, and they settled on a launch vehicle — we made our cost commitment,” Irace said following the conference.
According to a March 2009 U.S. Government Accountability Office report examining the cost and schedule performance of more than a dozen large-scale NASA projects, WISE encountered schedule delays early in its life cycle. The report states the project was not initially confirmed to proceed because of cost and technical concerns. As a result, the project team designed a smaller telescope and improved technologies identified by a confirmation review board as immature.
Although the project encountered some challenges during testing that affected the spacecraft’s design and increased costs by $2.6 million, the overall schedule was not affected, according to the report. During structural testing, a structural model of WISE’s flight cryostat — a vacuum flask filled with solid hydrogen to keep the spacecraft’s telescope and detectors chilled — failed.
“According to a NASA official, analyses done by NASA and the cryostat’s contractor did not predict this problem,” the report states. “To mitigate this problem, the project added a soft-ride system to the launch vehicle to reduce loads on the cryostat. The failure also caused the project to accept more project risk by de-scoping two test events in order to regain reserve margin.”
With years of budget and technical challenges behind it, the WISE team is looking forward to using the telescope to scan the sky with far better sensitivity and resolution than previous infrared surveys. The mission’s sensitive infrared telescope and detectors will be kept chilled inside the cryostat at minus 438 degrees Fahrenheit, preventing WISE from picking up the infrared signature of its own instrument.
In addition to near-Earth objects, WISE will find cool stars, known as brown dwarfs, which glow feebly like chunks of heated coal. By studying brown dwarfs, astronomers can learn more about star formation, as well as the atmospheres of planets orbiting stars beyond the sun.
“WISE is going to survey the whole sky and find these nearest neighbors and transform our view of the solar neighborhood,” said Peter Eisenhardt, WISE project scientist at the Jet Propulsion Laboratory. “It’s possible that one of these nearby brown dwarfs is even closer to the sun than any star that we now know of.”
The mission also will spot dusty nests of stars, swirling planet-forming disks and evolving galaxies.
“WISE has been designed so that it can detect these cataclysmic dusty forming galaxies out to a distance of 10 billion light years over the entire sky,” said Eisenhardt. “So we’re going to find the most super-duper, hyper-ultra luminous forming galaxies in the universe, and we’ll see just how extreme this galaxy-forming process can get.”
The mission will map the entire sky at four infrared wavelengths with sensitivity hundreds to hundreds of thousands of times greater than its predecessors, cataloging hundreds of millions of objects. The data will serve as a navigation chart of sorts for other missions, pointing them to the most interesting targets. NASA’s Hubble and Spitzer space telescopes, the European Space Agency’s Herschel Space Observatory, and NASA’s upcoming Sofia and James Webb Space Telescope will follow up on WISE finds.
“This is an exciting time for space telescopes,” said Jon Morse, Astrophysics Division director at NASA headquarters here. “Many of the telescopes will work together, each contributing different pieces to some of the most intriguing puzzles in our universe.”