SOHO, launched over six years ago as a project of international cooperation between the European Space Agency (ESA) and NASA, has discovered more than 420 comets in just under six years. This makes the spacecraft the most prolific comet finder in the history of astronomy. Most of the comets were first spotted by amateurs around the world who downloaded SOHO's real-time images to their home computers. Anyone with Internet access can take part in the hunt for new comets and be a comet discoverer.

http://www.gsfc.nasa.gov/news-release/releases/2002/h02-71.htm