Probing Earth

Human exploration of the solar system began with Earth. The first spacecraft were small unmanned craft launched into Earth's atmosphere. Improvements in space technology led to manned craft orbiting Earth.

Much of Earth has been studied without the aid of spacecraft. However, data from spacecraft confirmed much of what was known and enabled more accurate maps to be made. Pictures taken by spacecraft from space around Earth have helped scientists to predict weather and track hurricanes, for example.

Early in the space race, the USSR was active with its Sputnik, Vostok, Voskhod and Soyuz spacecraft. Early US spacecraft placed in Earth orbit included Explorer and those of the Mercury and Gemini programs. These early missions were the pioneers of future exploration of the Moon and other planets. For example, the 10 manned Gemini missions between 1964 and 1966 involved rendezvous between spacecraft in orbit, space walks, and dockings with unmanned target vehicles. The American Apollo program featured many spacecraft missions that eventually resulted in humans visiting the Moon (Earth's only natural satellite).

Today there are many artificial satellites in orbit around Earth. These are being used for many purposes, including communications, defence, science, navigation (including GPS) and weather monitoring. Orbiting

Table 6.2 Significant space probes used to monitor Earth


Country of origin



Explorer 1

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