The document summarizes major space exploration milestones from the 1950s-2000s. It describes the launch of Sputnik 1 as the first artificial satellite and Explorer 1 as the first US satellite. The US Pioneer program launched several early probes to study the Moon and Venus. In the 1960s-70s, Pioneer 10 became the first to travel through the asteroid belt and observe Jupiter. Pioneer 11 observed Jupiter and Saturn. The 1980s saw long duration SkyLab missions and the Soviet Salyut program, until the Challenger disaster in 1986. The 1990s included the launch of Hubble and Galileo and Mars rovers in the 2000s.