In 1981 the French Space Agency (CNES) circulated the French scientific community for ideas concerning Earth observation missions in order to define the scientific framework in which space missions would be integrated in the following 10 years. A geodesic laboratory proposed the realization of an altimeter, called Poseidon, to be carried on one satellite of the SPOT family, aiming to measure the distance between the surface and the satellite and hence contribute to developing a model of the geoid. The oceanographic community also joined and supported the project, as the measured distance permitted estimates of the sea level, which could give some clues on oceanic topography and circulation. It was eleven years later, in 1992, that the instrument Poseidon was finally launched, not on board a SPOT platform but as a part of an ambitious NASA's project, Topex/Poseidon. In 1999, after some years of observations, scientists in France and US separately published a similar result: sea level was rising at a rate of about 2-3mm/year. This figure was taken by the IPCC as evidence of global warming, included in its influential assessment report of 2001 (reiterating it also in 2007). Sea level rise became one of the key symbolic facts of environmentalism, a partisan object incarnating the existence of severe climatic change.

Satellites became the definitive technological vectors through which the sea level rise was brought to light. Actually, some tide gauge measurements made in situ already existed before the space age – which also indicated a tendency to sea level rise; nevertheless, it was the rise detected from space that was incorporated into the climatic change infrastructure. However, was this environmentalisation of a scientific result in turn taken by the space agencies and scientists to frame future satellite programs and research? Did scientific data resulting from Topex/Poseidon, considered as a herald of the global warming tenet, fuel the technological machinery to generate more data to support or modify those ideas? Satellite technology generated data, but was it at the same time conditioned by the data? In this paper I explore the considerations involving the selection and the conception of space missions at CNES, focusing in the altimetry missions as a case study, and examining to what extent environmental questions influenced satellite technology and space science development.