Explorer 3

Explorer Spacecraft Explorer Spacecraft

A model of the Explorer series of spacecraft. Image credit: NASA/JPL-Caltech
› Larger view

Mission Summary

Explorer 3 was the third satellite of the Explorer mission series and the first successful follow-on to Explorer 1, which made history when in January 1958 it became the United States' first space satellite. Like it's predecessor, Explorer 3 collected data confirming the theory that radiation belts trapped by Earth's magnetic field exist around the planet.

The Explorer series consisted of more than fifty satellites launched over a period of about 15 years. In 1960, NASA's Jet Propulsion Laboratory, which designed, built and operated the first five satellites of the series, turned the project over to NASA's Goddard Space Flight Center and turned its attention to planetary exploration with its Mariner, Ranger and Surveyor spacecraft projects.

Key Discoveries

Data from Explorer 3 -- combined with earlier measurements from Explorer 1 -- confirmed Principal Investigator James Van Allen's theory that radiation belts trapped by Earth's magnetic field exist around the planet.

Scientific Instrument(s)

- Cosmic-ray detector
- Micrometeorite detector

Type: Orbiter
Status: Past
Launch Date: March 26, 1958
17:31 UTC
Launch Location: Cape Canaveral Air Force Station, Florida
Mission End Date: June 27, 1958
Target: Earth
This view of Earth comes from NASA's Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite. NASA Celebrates Earth Day with Public Events and Online Activities

› Read more

Cleaned Solar Arrays Gleam in Mars Rover's New Selfie NASA Rover Opportunity's Selfie Shows Clean Machine

› Read more

Magdalena Ridge Observatory Exoplanets Soon to Gleam in the Eye of NESSI

› Read more