What efforts are being made to learn more about Comet 67P/Churyumov-Gerasimenko, while Rosetta is still en route?
Currently, an extraordinary ground-based effort is taking place to understand the physical condition of the comet. The Hubble Space Telescope has observed the comet, as has the European Southern Observatory’s New Technology Telescope. From now on, the comet will be tracked from Earth all the time, in an effort to learn as much as possible about its behaviour and composition. At present, the Rosetta science team believe that the comet is about four kilometres in diameter and almost as black as coal, reflecting only about 5% of the sunlight that strikes its surface. They will soon be observing the comet with the Spitzer Space Telescope (SIRTF), using its infrared capabilities to learn more. In particular, a key parameter to be determined is the density of the comet. Once this is known, in conjunction with its size, astronomers will be able to calculate its gravitational field. This is an essential parameter that must be known before Rosetta’s lander ‘Philae’ is released, as it affects th
