The scientific work of Pierre Léna is centred on infrared astronomy, a major branch of astronomy born in about 1960. With novel observations, he helped to model the solar atmosphere and its temperature minimum, then switched to the far infrared emission of molecular clouds in our Galaxy and the diffuse emission of interstellar medium observed with an airborne telescope.
He represented France on the governing Council of the European Southern Observatory (1986-1993), and directed the Graduate School of Astrophysics at Université Paris 7 (1976-1984 and 1992-1996) before becoming Director of the École Doctorale Astronomie d'Ile-de-France. His interest in educational matters led him to become President of the Institut National de Recherche Pédagogique (1991-1997) and to be an active member of La Main à la Pâte activity designed to renovate science education in schools. He was President of the Société Française de Physique in 1989 and from 2003 to 2007 President of the Comité d'éthique du CNRS. He built and was in charge of the Education office at the French Académie des sciences and became (2011) President of the new Foundation for science education, set by the Académie.