Timeline of first Earth observation satellites

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The timeline of first Earth observation satellites shows, in chronological order, those successful Earth observation satellites, that is, Earth satellites with a program of Earth science. Sputnik 1, while the first satellite ever launched, did not conduct Earth science. Explorer 1 was the first satellite to make an Earth science discovery when it found the Van Allen belts.

This list is incomplete; you can help by adding missing items. (August 2008)