Links to broadcast quality audio files and transcripts -- Dr. Scott Sandford, astrophysicist at NASA Ames Research Center, Moffett Field, Calif., was interviewed about the Stardust comet sample-return mission humanitys first opportunity to study the original material from which our solar system was built. Launched in 1999, the mission is flying to a rendezvous with the Wild-2 (pronounced VILD-TWO) comet in 2004 and is scheduled to return samples of cometary dust to Earth in 2006. The stardust mission is slated to be the first to return a sample from outside the Earths moon system. More information about the mission is on the Internet at: http://stardust.jpl.nasa.gov/
This interview was posted on the web April 28, 2003. Sandford provided these comments prior to a talk he gave about the mission at Foothill College, Los Altos Hills, Calif. on April 23.
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10. Why did you pick the Wild-2 comet?(1:49 minutes)
Dr. Scott Sandford: "Yeah, were largely going to Wild-2 for convenience. I mean most comets are on very elliptical orbits. They go very far from the sun, and they come in very close. And as a result, their velocities that they pass through the inner solar system in are very high. So, getting a spacecraft to visit a comet with a low relative encounter velocity is very difficult, and it takes very big motors or a lot of time to get in that kind of an orbit. Wild-2 has very conveniently been put in an orbit that makes it fairly easy to get to. And this is easy in a relative sense. But up until 1974 Wild-2 was in an orbit that never got closer to the sun than Jupiter, but in 74 it just missed hitting Jupiter, and it got flung into a new orbit, and that new orbit its in now the farthest its from the sun is Jupiter, but closest it gets is almost down to the Earth, and its also orbiting in the plane of the orbit of the Earth. So, theres no inclination as its called and so, as a result, we can get to it fairly easily without having to put giant rocket motors on the spacecraft, and still have modest encounter velocity. So, its largely been selected for its convenience in terms of getting there. On the other hand, we might have wanted to select it anyways because the fact that it was scattered into this new orbit in 1974 indicates that prior to that it didnt get near the sun much, so it probably didnt get altered much by getting heated by the sun. So, it may be that in some respects we could have a fairly fresh comet in a sense. Its not a comet like Halleys comet which has been around the sun maybe hundreds of times. And each time it passes around the sun, its been altered somewhat by the heating of the sun. So, ahh, the main reason were going is the orbit is convenient, but it may also be that scientifically, its a very good comet to visit."
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