page_title: List of uncrewed NASA missions
section_title: Explorers Program (1958–present)
hierarchical_section_title: List of uncrewed NASA missions / List of missions / Explorers Program (1958–present)
caption_attribution_description: English: Explorer 1 satellitePolski: Satelita Explorer 1
context_page_description: Since 1958, NASA has overseen more than 1,000 uncrewed missions into Earth orbit or beyond. It has both launched its own missions and provided funding for private-sector missions. A number of NASA missions, including the Explorers Program, Voyager program, and New Frontiers program, are ongoing.
context_section_description: The Explorer program has launched more than 90 missions since it began more than five decades ago. It has matured into one of NASA's lower-cost mission programs.
  The program started as a U.S. Army proposal to place a scientific satellite into orbit during the International Geophysical Year (1957–58). However, that proposal was rejected in favor of the U.S. Navy's Project Vanguard. The Explorer program was later reestablished to catch up with the Soviet Union after the launch of Sputnik 1 in October 1957. Explorer 1 was launched January 31, 1958; at this time the project still belonged to the Army Ballistic Missile Agency (ABMA) and the Jet Propulsion Laboratory (JPL). Besides being the first U.S. satellite, it is known for discovering the Van Allen radiation belt.
  The Explorer program was later transferred to NASA, which continued to use the name for an ongoing series of relatively small space missions, typically an artificial satellite with a science focus. Over the years, NASA has launched a series of Explorer spacecraft carrying a wide variety of scientific investigations.
caption: Explorer 1 satellite.
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