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Professor plots course for sun-studying spacecraft

WEST LAFAYETTE, Ind. -- A Purdue University professor and two of her doctoral students have designed the trajectory for an upcoming space mission, which may shed light on the composition of the sun.

Kathleen Howell, professor of aeronautical and astronautical engineering at Purdue, in collaboration with her students and Jet Propulsion Laboratory colleague Martin Lo, designed the trajectory for the spacecraft that will carry out the Genesis Mission, scheduled for launch in 2001 by the National Aeronautics and Space Administration. The primary goal of the mission is to collect solar wind particles -- material being swept out of the sun -- and return them to Earth for analysis.

The Genesis Mission is the newest addition to NASA's Discovery Class Program, which is charged with building lower-cost, highly focused scientific spacecraft.

The solar wind particles collected will include samples of isotopes of oxygen, nitrogen, the noble gases and other elements. The spacecraft will return the samples to Earth in 2003.

"This information can be used to validate theories concerning the composition of several objects in the solar system, including the sun and planetary atmospheres," Howell says. "To successfully collect these particles, the spacecraft must be beyond the magnetosphere of Earth. However, to keep the mission operation costs low, the spacecraft needs to remain as close to Earth as possible."

The trajectory Howell designed with her students, Brian Barden of West Lafayette and Roby Wilson of Vincennes, Ind., will put the spacecraft in "orbit" near a libration point in the sun-Earth system, nearly a million miles from Earth in the direction of the sun. A libration point, or Lagrange point, is where the gravitational pull from two or more heavenly bodies, plus the centrifugal force from their rotation, cancel each other out.

"These orbits are very complicated, much more complex than the orbit of a planet around the sun, which is why we often refer to the orbit as 'near' a libration point instead of 'around' a libration point," Howell says.

Howell, who has 15 years of experience in trajectory design for libration point missions, says a spacecraft in orbit near a libration point offers a stable venue for making observations and taking data. "Satellites in this region help us better understand the environment around the sun and Earth," she says. "A trajectory about one of these points is the ideal platform for this mission."

The spacecraft will gather solar particles for about two years before it returns to Earth, where it will be retrieved from the air over the Utah desert.

CONTACT: Howell, (765) 494-5786; e-mail,

Compiled by Amanda Siegfried, (765) 494-4709; e-mail,
Purdue News Service: (765) 494-2096; e-mail,

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