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.
Udupi Ramachandra Rao
Rao started his career as a cosmic ray scientist, and worked under Dr. Vikram Sarabhai, which he continued at MIT. In association with the JPL Group, he was the first to establish the continuous nature of the solar wind and its effect on geomagnetism using Mariner 2 observations. Rao's experiments on a number of Pioneer and Explorer spacecraft led to a complete understanding of the solar cosmic ray phenomena and the electromagnetic state of the interplanetary space. Convinced of the imperative need to use space technology for rapid development, Rao undertook the responsibility for the establishment of satellite technology in India in 1972. Under his guidance, beginning with the first Indian satellite "Aryabhata" in 1975, over 18 satellites including Bhaskara, APPLE, Rohini, INSAT-1 and INSAT-2 series of multipurpose satellites and the IRS-1A and IRS-1B remote sensing satellites were designed, fabricated and launched for providing communication, remote sensing and meteorological services.