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.
Soviet rocketry
Sputnik 1 was the first artificial Earth satellite ever launched. On October 4, 1957, the USSR launched Sputnik 1 into orbit and received transmissions from it. Sputnik 1 was designed to be the forerunner for multiple satellite missions. The technology constantly underwent upgrades as the weight of satellites increased. The first notable failure occurred during Sputnik 4, an unmanned test of the Vostok capsule. A guidance system malfunction pointed the capsule in the wrong direction for the orbit-exiting engine burn, sending it instead into a higher orbit, which decayed approximately four months later. The success of Sputnik 1 was followed by the launch of 175 meteorological rockets in the next two years. In all, there were ten of the Sputnik satellites launched.