Thursday, August 7, 2014

Rendezvous with a Comet

For the first time mankind will be landing on a comet in the next few months.  The European Space Agency launched Rosetta on March 2, 2004.  The purpose of the mission is to perform a detailed study of comet 67P/Churyumov–Gerasimenko. Until the last few weeks,
astronomers had no idea what the comet looks like.  After a long trip through space, in mid-July the spacecraft got close enough for scientists to get a closer look at the comet and realised that it has a very strange shape.  Rather than it being one comet, it is actually two comets joined together as
an offset binary comet. 

This week Rosetta advanced to less than 4000 kilometres from the comet.  In the next several days, it will fly within 70 kilometres of its surface during its first fly-by.  Since the comet does not have enough gravity to pull Rosetta into orbit, the satellite will spend several weeks flying around the comet in a series of equilateral triangles.  The purpose of these fly-byes is to map the entire surface of the comet, determine how much the comet is out-gassing, and to identify potential landing sites.   The schedule is for Rosetta to fly within a couple of kilometres above the surface on November 11th, before releasing the landing robot, Philae.

Comet Churyumov–Gerasimenko is a comet with a current orbital period of 6.45 years and a rotation period of approximately 12.7 hours. The comet will next come to perihelion (closest approach to the Sun) on 13 August 2015.  Like all comets, it is named after its discoverers, Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko, who first observed it on photographic plates in 1969.  It is interesting to know that the comet used to be twice the distance from the sun as compared to its current position.  However, in 1959 the comet had a close encounter with Jupiter, which changed its orbit and pushed it closer to the sun.

The size of the comet is only 3.5×4 km (2.2×2.5 mi).  Rosetta has travelled 400 million km to reach the comet, which is between the orbits of Mars and Jupiter.

ESA/Rosetta/NAVCAM – Collage/Processing: Marco Di Lorenzo/Ken Kremer-
ESA/Rosetta/NAVCAM/OSIRIS/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA Collage/Processing: Marco Di Lorenzo/Ken Kremer

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