DUGWAY PROVING GROUND — It looked like a graceful aerial ballet high above the bleak desert flats. In fact, Thursday's action was a dramatic practice run in which a helicopter snagged a simulated payload from space.

Although the payload was a dummy — a 240-pound, tublike weight carrying only monitoring electronics dropped by another helicopter — its payoff was real.

It was a practice run for ground controllers, pilots, radar technicians and scientists — one of several tests in which they are honing the skills they will need in September to capture a real probe that has gathered solar material in the depths of space.

When the Genesis capsule is snagged in midair above Dugway — scheduled Sept. 8 — the event will make history as the first retrieval of a U.S. space capsule above land. The capsule's contents should give scientists clues about the composition of the solar wind and possibly the formation of the planets.

Genesis was launched from Kennedy Space Center, Fla., on Aug. 8, 2001. The following December, when it was far beyond the moon, it began capturing samples of the solar wind — particles blowing away from the sun at more than 1 million mph.

The probe orbited a point in space called the "L1 Lagrange point," a location where the sun's and Earth's gravitation attractions are equally balanced. There, it gathered solar material on delicate sample collectors coated with gold, sapphire, diamond, silicone and aluminum. Particles from the solar wind are traveling so fast that some likely embedded themselves in the samplers.

Sample collection ended on April 2 of this year, and the devices were stowed back aboard the probe for the journey home.

At 5:43 a.m., Sept. 8, the sample return capsule is to separate from the spacecraft. It should re-enter the atmosphere at 9:55 a.m. somewhere above the Pacific Ocean. At an altitude of 21 miles, a drogue chute will pop out to slow the 5-foot-diameter, 420-pound capsule.

Genesis will be four miles up when the main parafoil deploys. This wing-shaped chute will slow it, allowing it to glide down at a relatively leisurely 26 mph. It should arrive over Dugway about 10:15 a.m. for capture by a pair of helicopters.

Snagging it in midair is essential to prevent a hard bump that could break the glass-like collectors.

Thursday morning, a helicopter left Dugway's Michael Army Air Field and climbed above the dense cloud cover. When it reached 11,000 feet above the desert (5,000 feet above the cloud tops), it released the weight.