Pierre Lacroute (1906–1993)

Pierre Lacroute passed away on 14 January 1993, a few days before reaching the age of 87. In 1946, shortly after the end of World War II, he was appointed Director of Strasbourg (France) Astronomical Observatory (succeeding André Danjon who was then taking up the directorship of Paris Observatory). Pierre Lacroute stayed in this position until his retirement in 1976. During the same period, he was also Professor at the Faculty of Sciences of Strasbourg Louis Pasteur University. He served also as Dean of this Faculty.

Pierre Lacroute will be remembered as a pioneer of space astrometry. Already in 1967, he was proposing an original technique based on the measurement of large angles from a space telescope. He refined this idea and finally got support from the European Space Agency. The Hipparcos satellite was born. Launched in 1989, Hipparcos initially encountered difficulties in achieving a correct orbit. Nowadays though, this satellite has completed its task of collecting data of an outstanding quality that will lead to a deep revision of the distance scale in the Universe. Astronomers from all over the world are participating in the programs of this satellite.

It would be a mistake to reduce Pierre Lacroute’s career to this single Hipparcos project, since his entire life was devoted to the development of measurement techniques of stellar positions and velocities. At the beginning of the 1970s, he also welcomed in his Observatory the Strasbourg Astronomical Data Centre (CDS) whose database SIMBAD is now serving the world astronomical community.

I came personally to know Pierre Lacroute around that time since I started my professional astronomical life with Jean Jung, first CDS Director. I was always impressed by his kindness, although he was molded in the old-style, somewhat authoritative, managerial approach, so typical of the elder generation. He never missed an opportunity to discuss his ideas (scientific or general), as well as his space projects such as Hipparcos, with young people, including the foreign visitor and beginner I was at the time. His famous “Comment dirais-je…” (“How could I say…”) will remain in the ears of all those who talked to him.

He was originally from Burgundy, a region he loved and where he has now been buried. He was a father of a large happy family. Pierre Lacroute was honored by several French distinctions and prizes, and it was fitting the he lived long enough after his retirement to see his brainchild Hipparcos successfully operational.