|
In 1999 NASA launched Stardust. A probe that then travelled 2.3 billion miles at 22, 043kph (13, 700 mph), then as it past the nucleus of a comet named Wild 2 (pronounced Vilt 2). Pictures were taken and dust samples collected.
The first pictured received from the Stardust where taken within (149 miles) of Wild 2' nucleus on 2nd January 2004. They revealed that the Wild 2 was a solid, rounded ball of ice and rock, covered with craters, flat-topped hills and canyons, surprising scientists who expected Wild 2 to be like many other asteroids, composed of debris held together by gravity. The comet is (3.3 miles) wide and its surface has two very distinctive craters, named Left Foot and Right Foot due to their shape resembling that of foot prints. Many other smaller, craters were also seen. It may be that the comet does not have enough gravity to absorb impacts hence the craters. Pictures also revealed networks of jets of spewing material from the core into space at supersonic speeds.
Stardust's total weight, including the propellant needed for deep space manoeuvres, is 380 kilograms. The overall length of the main body is 1.7 meters. The Stardust uses ultra pure hydrazine (N2H4) monopropellant in its propulsion system. Two non-gimballed solar arrays are deployed immediately after launch. They provide 6.6 square meters (71 sq. ft.) of solar energy to power the Stardust spacecraft, even when it is nearly three times farther from the sun than is the Earth. One nickel-hydrogen (NiH2) 16 amp-hour battery, using common pressure vessel (CPV) cell pairs, provides power during eclipses and for peak power operation.
Stardust also collected dust samples from the comet. It opened a grid filled with silica aerogel, the lowest density material known to mankind. This material captures thousands of particles, each less than a millimetre across.
Heavy-duty shields protect Stardust, as any collision, regardless of size of object collided with, could damage the Stardust significantly. Once samples have been collected a clam-like cover surrounds the sample and it is sent home. On 16th January 2004, a capsule containing the samples will re-enter the Earth's atmosphere and descend by parachute, landing in the Utah desert.
