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.
Kosmos 6
Kosmos 6 ( meaning "Cosmos 6"), also known as DS-P1 No.1 and occasionally in the West as Sputnik 16 was a prototype radar target satellite for anti-ballistic missile tests, which was launched by the Soviet Union in 1962. It was the sixth satellite to be designated under the Kosmos system, and the second spacecraft launched as part of the DS programme to successfully reach orbit, after Kosmos 1. Its primary mission was to demonstrate the necessary technologies for radar tracking of spacecraft, which would allow future satellites to function as targets. It was the first solar-powered satellite manufactured by Yuzhnoye.