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.
Carl E. Duckett
On October 4, 1957, America was shaken by the launch by the Soviet Union of the first artificial satellite, "Sputnik I". The U.S. Air Force and the CIA assembled a highly secret Telemetry and Beacon Analysis Committee (TABAC) to analyze the signals recorded from the launch at Tyuratam and those heard all over the world from "Sputnik". From his work in Jam Session, Duckett was asked to be a leader in the TABAC effort. It required about 18 months to calibrate the signals and understand how they related to the launch vehicle characteristics. The payoff, however, was significant; for the next two decades this provided the U.S a major window into the operation of Soviet missiles.