Image of the Month - February 2004

Rosetta Target

Originally, comet 46P/Wirtanen was selected as the target of the Rosetta spacecraft. Following a failure of the Ariane 5 rocket, Rosetta's journey had to be postponed, and a new target had to be selected. After checking several possible options, comet 67P/Churyumov-Gerasimenko was chosen. Liftoff of Rosetta is scheduled for February 26, 2004, when the European spacecraft will start a ten-year journey trough the solar system. The route will also take the spcaecraft into the asteroid belt twice, and a fly-by at one or more minor planets is currently considered. After reaching it's target in 2014, the spacecraft will swing into an orbit around the comet, and will even drop a small lander on it's icy nucleus.

Comet 67P/Churyumov-Gerasimenko was discovered in 1969 by Klim Ivanovic Churyumov and Svetlana Ivanovna Gerasimenko during observations of comet 32P/Comas-Sola at the Alma-Ata Astrophysical Institute. The comet is unusual in that it's perihelion distance was at least 4.0 AU only about 160 years back. Repeated encounters with Jupiter changed it's orbit so that the perihelion distance is currently only 1.3 AU, making this comet one of the "freshest" short-period comets knwon. 67P/Churyumov-Gerasimenko is also noted to have displayed outburst at perihelion at three of its last four returns to the inner solar system.

Credit & Copyright: Martin Christoph Tschimmel and Christoph Ries, Mt. Wendelstein observatory, Germany.
Color Composite by Herbert Raab, Austria. Click on the image above to see the full 825x825 pixel frame (383 kB).

The image shown here is a color composite assembled from three monochrome images, each a 300 second exposure, taken with the MONICA CCD imaging system at the 0.8m telescope of the Mt. Wendelstein observatory (Germany) trough green-yellow (V), red (R), and near-infrared (I) filters. The images were taken by Martin Tschimmel, on March 23, 2003 for photometric purporses. For astrometric data reduction, Christoph Ries later forewarded the images to Herbert Raab, who also combined the images to create this color composite, using the V-band image for the blue, the R-band image for the green, and the I-band image for the red color channel. The total magnitude of the comet, which boasts a tail about 4' in length in this image, was about 15mag at the time when the image was taken.

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