GENESIS TO CAPTURE PARTICLES FROM SUN IN MISSION.

Byline: Usha Sutliff Staff Writer

LA CANADA FLINTRIDGE - The JPL-managed Genesis mission will start its journey into space Tuesday to collect samples of solar particles and return them to Earth.

The mission, to launch from Florida's Cape Canaveral Air Force Station, will collect invisible, charged particles flung from the sun and return in 2004.

The probe will be maneuvered to a point in space between the Earth and sun, dubbed L1, where the gravitational pull of both bodies is in balance. Just under 1 million miles away from our planet, Genesis will be well beyond Earth's atmosphere and magnetic environment.

During five passes lasting six months each, unfurled collectors will gather about 10 to 20 micrograms - the weight of a few grains of salt - of particles from the solar wind.

Scientists want to study the samples to learn more about how the solar system was formed and the exact composition of our star.

``The mission will be the Rosetta Stone of planetary science data, because it will show us the foundation by which we can judge how our solar system evolved,'' said Chet Sasaki, Genesis project manager at JPL.

``The samples that Genesis returns will show us the composition of the original solar nebula that formed the planets, asteroids, comets and the sun we know today.''

Aside from the bicycle tire-sized solar wind collector arrays, Genesis will carry ion and electron monitors and an ion concentrator that will separate out elements such as oxygen and nitrogen in the solar wind into a special collector tile.

Caltech's Don Burnett, principal investigator and leader of the mission, said Genesis will return a small but precious amount of data.

``If you don't count hydrogen and helium, which we're not interested in, the mass of material returned would indeed be equal to a few grains of salt,'' Burnett said. ``But to our way of thinking, this is almost a billion-billion atoms, which is a lot.''

The mission will be the first to return a sample of extraterrestrial material collected beyond the orbit of the moon, according to JPL.

In September 2004, specially trained helicopter pilots will catch Genesis' sample return capsule in midair over the Utah desert to spare the delicate particles a jarring landing. It's not nearly as risky as it sounds, Burnett said.

``We have two helicopters, and between them, they get five chances to catch the parachute before it hits the ground,'' he said. ``We practiced this many times and it has always been successful the first time.''

The samples will be taken to the National Aeronautics and Space Administration's Johnson Space Center in Houston, where they will be stored and distributed for study. Genesis is the fifth mission in NASA's Discovery Program, which sponsors low-cost solar system exploration projects with highly focused scientific goals.

The Genesis spacecraft and science instruments cost $164 million, while mission operations and science data analysis will cost $45 million.

Starting at 8 a.m. PDT, people who want to see the launch can log on to www.jpl.nasa.gov/webcast/genesis-launch/. The launch window for Genesis will open at 9:36 a.m.