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Northrop Grumman Concept Uses Shade to Find New Planets

Northrop Grumman Space Technology is investing in what itsays is a cheaper way to image Earth-size planets orbiting neighboring stars.

Dubbed New Worlds Observer, the planet-finding concept isthe brainchild of Webster Cash, an astronomy professor at the University of Coloradoat Boulder. Cash initially developed the idea under a grant from the NASAInstitute for Advanced Concepts.

Cash, with Northrop Grumman's backing, submitted a proposalto NASA this year to build and launch a free-flying star shade that would workin tandem with the James Webb Space Telescope to search out and image anyEarth-sized planets that may be hiding in nearby solar systems. Star shades, orocculters, work by blocking out a star's light to reveal dim objects hidden intheir glow.

With an estimated price tag of around $425 million, the NewWorlds Observer would cost a fraction of the Terrestrial Planet Finder, amultibillion-dollar pair of planet-hunting telescopes that NASA has beentalking about for years. The agency recently decided to put that idea onindefinite hold while it finishes other major space telescope projects, likeWebb, already in development.

When NASA selected its latest crop of Discovery-classmission candidates this fall, it passed on the New Worlds Observer proposal.NASA's Discovery Program funds competitively selected deep space missions thatcan be accomplished for no more than $425 million.

Redondo Beach, Calif.-based Northrop Grumman SpaceTechnology is continuing to refine the New Worlds Observer idea using anundisclosed amount of internal research and development funds.

Amy Lo, Northrop Grumman's systems engineer on the NewWorlds Observer, said the company is preparing experiments for the year aheadmeant to show that the novel approach would work.

The concept entails a large flower-petal-shaped star shadethat would be positioned thousands of kilometers away from Webb but directly inits line of sight to a nearby star system. The shade would, in effect, blockout the light from the star so that Webb could pick up fainter objects in thatgeneral vicinity--planets.

The free-flying star shade would be tens of meters acrossand probably made out of Kapton, Lo said, a strong but lightweight materialsimilar to Mylar.

Lo said that while the New Worlds Observer approach worksespecially well with the James Webb Space Telescope, the idea can work with amuch simpler telescope. A 2-meter or larger optical aperture, she said, shouldbe sufficient.

The Hubble Space Telescope, which will have a new lease onlife if NASA pulls off a successful servicing mission in 2008, is not wellsuited to work in tandem with the New Worlds Observer, Lo said.

"If Hubble was in the right orbit, it would work perfectlyfine," she said.

The problem with Hubble, Lo said, is that it is "whizzing bytoo fast for the occulter to line up."

Hubble, located some 600 kilometers above the Earth, orbitsabout every 96 minutes. In its higher orbit, "the occulter would have to moveeven faster to stay lined up," Lo said. "It's really not feasible."

"A better place would be someplace like the second Lagrangepoint where James Webb will be," Lo said.

The Lagrange point 2, located 1.5 million kilometers from Earth,is considered a good location for an observatory like Webb because its uniquegravitational properties will keep the telescope constantly on the nighttimeside of the Earth as it circles the sun.

To put the New Worlds Observer concept to the test, NorthropGrumman is heading to the laboratory. Lo said the company is building verysmall, subscale occulters--about 50 millimeters across--and testing them out onan optics bench to make sure the approach works.

"The reason we have to make them so small is we've got thisscale problem," she said.

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