These changes may include the effects of global warming, stratospheric ozone depletion, and large-scale changes in land cover due to human activities such as biomass burning. In the 1960s, the desire to monitor the Earth's environment was linked with new technology that enabled us to observe our planet from space - giving humans our first global view of Earth.
Today there are hundreds of artificial satellites in orbit around the Earth.
These satellites are used for many purposes, such as communications, weather forecasting, and navigation, as well as observing the Earth. Satellites used to observe the Earth carry a variety of instruments to study the land, ocean, air and life, as well as their interactions. Scientists at NASA's Langley Research Center use several satellites now in orbit to measure some very specific atmospheric phenomena, such as the amount of ozone in the atmosphere, and to help them distinguish between environmental changes caused by humans and those that occur naturally. The technology used on a satellite varies, depending on its mission. Computers aboard a satellite can receive, store and transmit information in the form of radio signals sent to and from stations on Earth.