The International Space Year was 1992, the year of the quincentenary of Christopher Columbus's voyage to the Americas in 1492. First proposed by U.S. Senator Spark Matsunaga, the designation of 1992 as International Space Year was endorsed by 18 national and international space agencies, who also proposed the year's theme, "Mission to Planet Earth". Eventually, 29 national space agencies and 10 international organizations took part in coordinated activities to promote space exploration and the use of sustainable technology on Earth.