The TOPEX/POSEIDON satellite mission to observe the oceans triggered the formation of the new specialty of space oceanography from the 1970s to 1990s. Previously, in the 1960s in the United States, traditional oceanographers had shown little interest in the possibilities of space and thus space engineers and physicists worked on the first missions (Seasat in particular). TOPEX/POSEIDON brought together two projects, one American (TOPEX) and the other French (POSEIDON). The gradual crystallization of the disciplinary specialty of space oceanography occurred by making available a platform of instruments able to meet an ensemble of varied needs. Battery failures just before the launch of the joint mission meant that the mission had to focus on the essentials (notably El Niño effects). Subsequently, the discovery of a significant rise in sea levels due to global warming resulted in space oceanography becoming a recognized specialty. The case of TOPEX/POSEIDON shows the original ways in which instruments gained a place in the very large range of oceanographic techniques.