Observing the Earth: An international endeavour

“Achieving comprehensive, coordinated, and sustained Earth observations for the benefit of humankind.” The need to collect, organize, standardize Earth observation data for the benefit of a planetary community of users has been recognized since more than a century: in the recent period, after World War Two, the ‘World Meteorological Convention’ adopted a strategy in Washington in 1947, which led to the creation of WMO in 1951 (World Meteorological Organization). An important step took place, next, when ICSU (International Council of Scientific Unions now named International Council for Science), upon a suggestion of Lloyd Berkner, initiated in 1952 the organization of the International Geophysical Year (1957–1958) with a special focus on Earth observation from space. Indeed, the launching of Earth observation satellites was put forward as one of the major objectives of IGY (International Geophysical Year). This goal was reached beautifully with the successful launches of Sputnik on 4 October 1957 by the USSR and of Explorer I on 31 January 1958 by the USA. Sputnik, purposely spherically shaped, brought the first high-altitude atmospheric data through the observation of the drag exerted by the atmosphere on the spacecraft. Explorer I, equipped with a Geiger counter, led to the discovery of the ‘Van Allen belts’ surrounding the Earth. The development, at a tremendous pace, of experimental satellites observing the Earth, the planets, and the Universe followed then immediately. As early as 1960, the concept of meteorology satellites emerged with the launch of the first weather satellite in polar orbit, TIROS. It took then almost 20 years before reaching the stage of implementing operational meteorological satellites in polar sun-synchronous or in geostationary orbits: at that time, meteorologists had learned how to incorporate meteorological space data into weather-forecast systems. The aim of this paper is to describe schematically the gradual implementation of an Earth observation system of systems associating in situ and space observations as well as numerical modelling in order to provide humankind with the necessary tools for Earth science, sustainable development, and security. To cite this article: P. Baüer et al., C. R. Geoscience 338 (2006).