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Spacecraft to return comet sample January 15

Launched in February 1999, NASA's Stardust spacecraft will soon return to Earth with comet samples.
For more information, contact:
Matt Quandt
Assistant editor
Astronomy magazine
[t] 262.796.8776 x419

January 10, 2006

Astronomy offers publication-quality images below.

WAUKESHA, WI &#151 Since its launch February 7, 1999, NASA's Stardust spacecraft has been on an historic mission to encounter Comet Wild 2 (pronounced "Vilt") and collect minuscule specks of dust with its dust-collecting instrument. On Sunday, it returns to Earth with those samples in tow.

On January 15, the craft's sample-return capsule will be hurled into Earth's atmosphere at a whopping 28,860 miles per hour (46,440 km/h), the fastest return speed of any spacecraft ever entering Earth's atmosphere.

A porous, spongy substance called aerogel aided in collecting grain-size dust samples from the comet's coma, an envelope of gas and dust that surrounds a comet's solid nucleus. Small blocks of aerogel 0.39-inch (1 cm) and 1.18-inches (3 cm) thick mounted within the dust collector's aluminum grid slowed down and captured the high-velocity particles with minimal damage from heating.

The dust collector is a two-sided instrument. One side collected cometary dust particles, while the other side collected interstellar dust particles. Once collected, a total of 28 grams of these particles were folded inside the dust collector's sample canister and stowed for the journey back to Earth.

The spacecraft's Sample Return Capsule consists of a sample canister, heat shield, and parachute. This capsule will free fall after entering Earth's atmosphere until it reaches about 2 miles (3 km) above Earth's surface. Then, its parachute is expected to deploy. A descent chute will help slow the capsule, and a UHF beacon will allow mission scientists to track the capsule by ground radar.

NASA plans for the capsule to land at the Utah Test and Training Range within a 52-mile (84 km) by 19-mile (30 km) landing footprint. Once the capsule's on the ground, either a helicopter or ground vehicles will retrieve it. Ultimately, the canister will be moved to the Johnson Space Center in Houston. For planetary scientists eagerly awaiting their chance to study these particles, the wait will soon be over.

Discovered in 1978, Comet Wild 2 takes approximately 6.39 years to orbit the Sun. It travels as close to the Sun as Mars and as far away as Jupiter.

An identified flying object
From 1:56 a.m. PST to 1:58 a.m. Sunday, people living in an area from San Francisco to Salt Lake City to Seattle will have the chance to see the capsule streak across the sky. The capsule will reach maximum heating and, thus, be at its brightest, at 1:57:31 a.m. PST as it passes east of Winnemucca, Nevada, over Interstate 80 at an altitude of 37 miles (61 km). It will take the capsule only about a minute to travel from the northwest coast of California to the Test and Training Range in northwestern Utah.

Also in the sky
That same morning, January 15, at 8 a.m. EST, the Moon passes just 4° north of Saturn. The Full Moon appears 1/2° wide, so Saturn will be about 8 Full-Moon widths from the Moon.

January 17, 2006: The launch window opens for New Horizons &#151 the first mission to the last planet, Pluto.
Stardust capsule's descent path
Anyone within the light area will have the chance to see Stardust's capsule streak across the sky around 1:57 a.m. PST. The farther you are from the "Capsule's projected path," the lower in the sky the streak will appear.
Astronomy: Francis Reddy and Roen Kelly
The Stardust spacecraft intercepted Comet Wild 2 on January 2, 2004.
Comet Wild 2
On January 2, 2004, Stardust flew within about 230 kilometers (150 miles) of Comet Wild 2's nucleus. This photo shows one hemisphere of the nucleus in sunlight and the other in shadow, similar to a view of the quarter Moon from Earth. The nucleus is estimated to be about 5 km (3.1 miles wide).


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