'Stardust' Spacecraft Closes in on Comet

400 million kilometers from Earth, an epic five year-long voyage through space is approaching its climax, as Stardust speeds towards its fly-by of comet Wild-2. Having traveled over 3 billion miles to get there, the spacecraft is now less than million kilometers away from the comet. On Friday, January 2 2004, at 11:40:35 am Pacific Standard Time, Stardust will pass only 300 kilometers (190 miles) from the surface of Wild 2's nucleus. It will be traveling at a relative speed of 21,960 kilometers per hour (13,650 mph), more than six times the speed of a rifle shot.

"In recent decades spacecraft have passed fairly close to comets and provided us with excellent data," said Dr. Don Brownlee of the University of Washington, principal investigator for the Stardust mission. "Stardust, however, marks the first time that we have ever collected samples from a comet and brought them back to Earth for study."

In preparation for the big day, the spacecraft, which has been largely dormant for nearly a year, is gradually coming back to life. Since November 19, Stardust's navigation camera has been repeatedly taking pictures of the comet, which has grown steadily from a point of light to a fuzzy dot as the distance between spacecraft and comet narrowed. On December 23 Stardust fired its rockets, making the final trajectory corrections before new year's eve. On the following day it extended its unique tennis racquet-shaped dust-catching arm.

Acquiring "fresh and pristine" particles is especially important for scientists on Earth, waiting eagerly to study the samples returned by Stardust. Comets are primordial objects, left unchanged since the formation of the Solar System 4.5 billion years ago. Their composition can tell scientists a great deal about the conditions that prevailed at that time, and about the origins and evolution of the planetary system we know today. Furthermore, some scientists believe that comets played a crucial role in the development of life on Earth. In this view, some of the building blocks of life, including water and carbon, were not present in the early Earth but were plentiful on comets. The evolution of life as we know it became possible, according to this theory, when the Earth was bombarded by comets in its early years, seeding the planet with those crucial components. The close examination of actual cometary dust will go a long way in determining the validity of these theories. Obtaining such samples is Stardust's primary mission.

"The samples we will collect are extremely small, 10-300 microns in diameter, and can only be studies in laboratories with sophisticated analytical instruments" said Brownlee. "The analyses will be done a single grain at a time."

http://spaceflightnow.com/stardust/status.html

FRIDAY, JANUARY 2, 2004

0501 GMT (12:01 a.m. EST)

The Stardust space probe is headed for the defining moment of its $168 million, seven-year mission to gather particles swirling around the heart of Comet Wild 2.

At about 2:19 p.m. EST (1919 GMT) today, the craft and comet will pass just 186 miles (300 kilometers) from each other at a relative speed of 13,650 miles per hour (22,000 kph). Controllers on Earth will be monitoring the event, but it takes over 20 minutes for a signal to travel the 242 million miles (389 million kilometers) from Stardust.

There is no doubt that the encounter is dangerous, NASA officials acknowledge. "In order to collect these particles, we have to put our spacecraft in harms way. We have to fly through the coma of Wild 2. This is a tremendously severe environment," said Tom Duxbury, the Stardust program manager.

"This is leading-edge planetary exploration where we have an extreme, severe environment when we go through a storm of dust particles at over six times the speed of a bullet. "We have done all of the homework, we have done all of our designs and testing on the ground, we have practiced for five years. So even though there is risk, and with planetary exploration we know there aren't any guarantees, we have done everything possible to prepare for our encounter."

If all goes well, the spacecraft will successfully emerge from the comet's dust and gas cloud with its priceless cargo. Stardust's trek ends in January 2006 with the comet samples landing back on Earth inside a protective capsule. We will be providing live updates on this page during and after today's comet encounter.

It's armored just in case a particle is bigger than expected. This site [ http://spaceflightnow.com/stardust/status.html ] will be updated frequently.

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