Rosetta Spacecraft - Sergei Gulyaev
If you ever wondered how to measure a comet, you're just about to find out. The Rosetta space craft successfully landed a probe on a comet (Comet-67P) last year. And current predictions are that it's 10 billion tonnes - or about the size of Mount Everest. But, scientists think this may be wrong. Professor Sergei Gulyaev is the founder and director of AUT's Institute for Radio Astronomy and Space Research. He's been helping the European Space Agency to find out just how big it is.