Northrop Grumman Space Technology is investing in what it
says is a cheaper way to image Earth-size planets orbiting neighboring stars.
Dubbed New Worlds Observer, the planet-finding concept is
the brainchild of Webster Cash, an astronomy professor at the University of Colorado
at Boulder. Cash initially developed the idea under a grant from the NASA
Institute for Advanced Concepts.
Cash, with Northrop Grumman's backing, submitted a proposal
to NASA this year to build and launch a free-flying star shade that would work
in tandem with the James Webb Space Telescope to search out and image any
Earth-sized planets that may be hiding in nearby solar systems. Star shades, or
occulters, work by blocking out a star's light to reveal dim objects hidden in
their glow.
With an estimated price tag of around $425 million, the New
Worlds Observer would cost a fraction of the Terrestrial Planet Finder, a
multibillion-dollar pair of planet-hunting telescopes that NASA has been
talking about for years. The agency recently decided to put that idea on
indefinite hold while it finishes other major space telescope projects, like
Webb, already in development.
When NASA selected its latest crop of Discovery-class
mission candidates this fall, it passed on the New Worlds Observer proposal.
NASA's Discovery Program funds competitively selected deep space missions that
can be accomplished for no more than $425 million.
Redondo Beach, Calif.-based Northrop Grumman Space
Technology is continuing to refine the New Worlds Observer idea using an
undisclosed amount of internal research and development funds.
Amy Lo, Northrop Grumman's systems engineer on the New
Worlds Observer, said the company is preparing experiments for the year ahead
meant to show that the novel approach would work.
The concept entails a large flower-petal-shaped star shade
that would be positioned thousands of kilometers away from Webb but directly in
its line of sight to a nearby star system. The shade would, in effect, block
out the light from the star so that Webb could pick up fainter objects in that
general vicinity--planets.
The free-flying star shade would be tens of meters across
and probably made out of Kapton, Lo said, a strong but lightweight material
similar to Mylar.
Lo said that while the New Worlds Observer approach works
especially well with the James Webb Space Telescope, the idea can work with a
much simpler telescope. A 2-meter or larger optical aperture, she said, should
be sufficient.
The Hubble Space Telescope, which will have a new lease on
life if NASA pulls off a successful servicing mission in 2008, is not well
suited to work in tandem with the New Worlds Observer, Lo said.
"If Hubble was in the right orbit, it would work perfectly
fine," she said.
The problem with Hubble, Lo said, is that it is "whizzing by
too fast for the occulter to line up."
Hubble, located some 600 kilometers above the Earth, orbits
about every 96 minutes. In its higher orbit, "the occulter would have to move
even faster to stay lined up," Lo said. "It's really not feasible."
"A better place would be someplace like the second Lagrange
point 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 unique
gravitational properties will keep the telescope constantly on the nighttime
side of the Earth as it circles the sun.
To put the New Worlds Observer concept to the test, Northrop
Grumman is heading to the laboratory. Lo said the company is building very
small, subscale occulters--about 50 millimeters across--and testing them out on
an optics bench to make sure the approach works.
"The reason we have to make them so small is we've got this
scale problem," she said.
