Currently, ## scientific satellites are in orbit around the Earth. These satellites address a wide array of scientific issues. For example, NASA characterizes scientific satellites by the following types: astronomy, earth science, planetary science, solar physics, space physics, life science, and microgravity.
Non-U.S. military estimates, which are for 2004, include the following countries: United Kingdom, France, Russia, Germany, Belgium, Spain, Italy, and Israel. China’s budget includes both military and civil expenditures. Note that the estimate of China’s space budget is controversial. At a NASA budget hearing in April 2006, much of the discussion was about the possible size of China’s space program and its ability to complete its plans to land astronauts on the Moon in 2017.
Space-based platforms provide unique opportunities for microgravity research and international scientific cooperation. The ISS, the space shuttles, Skylab, Russia’s Mir Space Station and Soyuz, and the Chinese Shenzhou have enabled microgravity research.
More than ## missions carrying scientific instruments, in the form of probes and rovers, have been launched into the solar system to study planets, comets, asteroids, and other phenomena. These instruments return valuable scientific data on the history and nature of the solar system. Recently, NASA launched the New Horizons probe in January 2006 to study Pluto.
China’s Shenzhou (“Divine Vessel”) launched two taikonauts into orbit in 2005 for a mission lasting more than 115 hours. It was China’s second human launch, following the launch of one taikonaut in October 2003. China’s next human mission is expected to launch in 2007. The Shenzhou capsule bears many design similarities to Russia’s Soyuz reentry crew capsule.