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.
Fred Singer
Singer was one of the first scientists to urge the launching of earth satellites for scientific observation during the 1950s. In 1951 or 1952 he proposed the MOUSE ("Minimal Orbital Unmanned Satellite, Earth"), a satellite that would contain Geiger counters for measuring cosmic rays, photo cells for scanning the Earth, telemetry electronics for sending data back to Earth, a magnetic data storage device, and rudimentary solar energy cells. Although MOUSE never flew, the "Baltimore News Post" reported in 1957 that had Singer's arguments about the need for satellites been heeded, the U.S. could have beaten Russia by launching the first earth satellite. He also proposed (along with R. C. Wentworth) that satellite measurement of ultraviolet backscatter could be used as a method to measure atmospheric ozone profiles. This technique was later used on early weather satellites.