Louis XIV and Colbert wished to attract the best foreign specialists to France to develop science, commerce and industry. In the case of astronomy, Giovanni-Domenico Cassini (1625-1712), from Bologna, Italy, was a great specialist on the motions of Jupiter’s satellites. In effect, the Observatory hoped to use these satellites as aids to determine one’s longitude on the sea and on land, a crucial problem for cartography and navigation. Cassini accepted the invitation, Gallicised his first names into Jean-Dominique, was naturalized and in 1673 married Geneviève de Laistre. They had a daughter and two sons. One of the sons, Jacques, became in turn director of the Observatory.

caption : Cassini’s portrait - copyright : Observatoire de Paris