French Ministry of Culture classified the building, bequeathed the entire site to the Socit Astronomique de France  but did not sign a lease.
Flammarion's second wife, Gabrielle Renaudot Flammarion, bequeathed the entire site to the Societe Astronomique de France upon her death in 1962. In 1971, the society signed a 99-year lease with the municipality of Juvisy to ensure the site's maintenance, preservation and accessibility. 
