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.
J. Allen Hynek
In 1956, he left to join Professor Fred Whipple, the Harvard astronomer, at the Smithsonian Astrophysical Observatory, which had combined with the Harvard Observatory at Harvard. Hynek had the assignment of directing the tracking of an American space satellite, a project for the International Geophysical Year in 1956 and thereafter. In addition to over 200 teams of amateur scientists around the world that were part of Operation Moonwatch, there were also 12 photographic Baker-Nunn stations. A special camera was devised for the task and a prototype was built and tested and then stripped apart again when, on Oct. 4, 1957, the Soviet Union launched its first satellite, Sputnik 1.