Fifty three years ago, on 31 January 1958, the first satellite for the observation of Earth was launched. Explorer 1 was the first satellite sent into orbit by the United States of America. In October 1957 the Soviet Union launched Sputnik 1 into space thus beginning the Cold War space race.
Both Sputnik 1 and Sputnik 2 intended only to test the possibilities and methods to bring a manmade object into space. Explorer 1, on the contrary, was built to gather data about our planet. The year 1958 was announced as the International Geophysical Year and was the year of the first satellite remote sensing project. Explorer 1, with a total weight of only 14 kilograms, was armed with magnetic sensors and transmitted data for only one month despite remaining in orbit for more than 12 years. After more than 58,000 orbits, a total distance of nearly 2.5 billion kilometres, Explorer 1 re-entered the atmosphere in March 1970.
Today, more than 2,000 satellites are circling the Earth. Some are communication satellites only, but most satellites are built to observe the Earth. Optical systems on satellites like GeoEye or RapidEye (both private) allow optical resolutions of up to 50 centimetres, providing spectacular views of the Earth surface.
Satellite missions like GRACE (Nasa and DLR) and GOCE (ESA) showed that we can view our planet by interpreting gravitational data collected by satellites. Missions like ESA’s CryoSat or SMOS provide important data to understand sub-systems like the global oceans conveyor belt or the effects of soil moisture on regional climate behaviour.
Today we celebrate 53 years of satellite remote sensing and how it has shown us that sometimes we need to step back and look at the big picture to reveal the details.