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.
Bradford Parkinson
Beginning with the landmark launch of Sputnik in 1957, the first man-made satellite, members of the aeronautical and military spheres realized that satellite-based positioning was technically feasible, perhaps likely. The United States Navy experimented with the technology in 1960, launching the Transit positioning satellites which was mainly used for submarine navigation, in particular for initializing their on-board ballistic missiles. However, Transit only provided two-dimensional, periodic fixes every several hours with an accuracy of about 1/10th to 1/4 mile. Additional, satellite-based, navigation systems were proposed or launched throughout the 1960s including by the USAF/Aerospace Corporation, the Johns Hopkins Applied Physics Laboratory, and the Naval Research Laboratory. But because of the secrecy and competition for budgets, of such military endeavors, collaboration was minimal. Also, their collective promise of accuracy was not credible to Pentagon officials and they publicly voiced their skepticism of the whole premise. They did not believe the usefulness would justify the cost. Parkinson was met with extreme resistance, but used small-scale prototypes sell what would go on to become GPS.