STEREO - Solar Terrestrial Relations Observatory
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Important notice about STEREO Behind

Spotting Asteroid Vesta - January 16, 2008

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Beginning late on January 16 2008 the asteroid Vesta appeared in the STEREO SECCHI COR2-A ("Ahead" spacecraft) images. Although a fairly small, whitish dot, it can be picked out in the lower-left corner, moving left-to-right noticeably slower than the star field that passes behind it. Vesta is the second most massive asteroid that we know of, about the size of the state of Arizona. It has a very complex surface that bears the scars of countless ancient impacts, some of which have left craters deep enough for astronomers to peer below the asteroid's crust and into the past. In fact, the NASA's Dawn mission launched in late 2007 to begin an 8-year, 3.2-billion-mile odyssey to explore Vesta in 2011 and Ceres, another asteroid, in 2015 [ link: http://dawn.jpl.nasa.gov/ ].

The appearance of Vesta in SECCHI COR2-A is not a particularly big deal in and of itself -- SOHO's LASCO C3 coronagraph has observed Vesta several times and the wider-field SECCHI HI (Heliospheric Imager) instruments sees several asteroids on any given day. However, this is a first for COR2 and will be a reasonably rare event given the relatively small COR2 field of view. Additionally, the high-resolution of the COR2 instrument gives us the sharpest view STEREO will ever obtain of this ancient object. (Note that the cadence of the movie speeds up towards the end of the clip.) Vesta will leave the COR2-A field of view by early next week and should appear in the COR2-B ("Behind" spacecraft) sometime in March, extending our view of Vesta for just a little longer.


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