Earth observation satellite
Earth observation satellites or Earth remote sensing satellites are satellites specifically designed for Earth observation from orbit, similar to spy satellites but intended for non-military uses such as environmental monitoring, meteorology, map making etc. 
The first occurrence of satellite remote sensing can be dated to the launch of the first artificial satellite, Sputnik 1, by the Soviet Union on October 4, 1957. Sputnik 1 sent back radio signals, which scientists used to study the ionosphere.
NASA launched the first American satellite, Explorer 1, in January 31, 1958. The information sent back from its radiation detector led to the discovery of the Earth's Van Allen radiation belts.
The TIROS-1 spacecraft, launched on April 1, 1960 as part of NASA's TIROS (Television Infrared Observation Satellite) Program, sent back the first television footage of weather patterns to be taken from space.
, more than 150 Earth observation satellites were in orbit, recording data with both passive and active sensors and acquiring more than 10 terabits of data daily.
The Princeton Three
October 4, 1957 the Soviet Union put the first satellite into orbit around the Earth. Sputnik one caused many in the U.S. scientific community to outburst on the lack of work put into a satellite program. One of the key contributors to these outbursts was a former German scientist, turned American through project paperclip, Wernher von Braun. Von Braun stated that if given the correct materials and the go ahead he would have an American satellite in orbit in a matter of months, and he did not disappoint. January 31, 1958, two months after the Soviets launch their second satellite, Sputnik II, into orbit Explorer I, the first American satellite, was launched into orbit. The Soviets launch of Sputnik I and Sputnik II showed that America was falling behind in fall facets of scientific research only adding to the need of a national laboratory set aside for scientific research according to the issues present.