Stardust flies by Earth today
Posted by Emily Lakdawalla
14-01-2009 14:26 CST
In less than two hours, Stardust will approach to within 10,000 kilometers of Earth, getting a gravity assist that will target it for a February 14, 2011 encounter with comet Tempel 1, once the target of the Deep Impact mission. This page from the Stardust-NExT mission (the official name of Stardust's extended mission to Tempel 1) says that just before the flyby, the spacecraft was commanded to take some calibration photos targeting the Moon. There was some concern that during Stardust's original mission, when it flew through the coma of comet Wild-2, the mirrors on its periscope may have gotten pitted by cometary particles, which would have reduced the quality of its camera's images. (Stardust has the periscope to make sure that the camera's optics aren't themselves flying face-on into cometary particles, so that if anything got damaged, it would be the mirrors in the periscope, not the camera itself.) Here are two photos of the Moon taken two days ago, with and without the periscope in the optical path. (The Stardust website did not actually indicate which of these images was taken with the periscope, and which without.)Don't be too underwhelmed. These pictures were taken from pretty far away, and the camera on Stardust is not one of its primary science instruments -- it's an engineering camera, a navigational tool. As a reminder, here a montage of the best Stardust images of its original quarry, Wild-2, at their original resolution (once you enlarge them; they're at about 1/3 their original resolution below. Realize that Stardust was less than 300 kilometers away from Wild 2 when it took these photos). ...and, for completeness, here's one of Stardust's other catches, the small asteroid Annefrank. Stardust is actually the second spacecraft to fly by Earth in a month. Deep Impact came by, too, on December 28. It was a pretty distant flyby, at 43,000 kilometers. Both spacecraft were challenging targets for amateur astronomers. Deep Impact was much farther away, so fewer astronomers seem to have caught it, but people have been having better luck spotting and photographing Stardust as it passes by; several photos are posted at the Minor Planets Mailing List..
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