Pierre Lacroute (1906–1993), was a French astrophysicist and pioneer of

astrometry Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other Astronomical object, celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, th ...

using satellite experiments. He is known as the first proposer of the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of ...

space experiment.

Education and career

After graduating in physics at

École normale supérieure École or Ecole may refer to: * an elementary school in the French educational stages normally followed by Secondary education in France, secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing i ...

, Pierre Lacroute received a doctorate in physical sciences from the Faculty of Sciences of the

University of Paris The University of Paris (), known Metonymy, metonymically as the Sorbonne (), was the leading university in Paris, France, from 1150 to 1970, except for 1793–1806 during the French Revolution. Emerging around 1150 as a corporation associated wit ...

in 1934. His Ph.D. thesis entitled ''Effet Zeeman du brome et de l'iode'' (

Zeeman effect The Zeeman effect () is the splitting of a spectral line into several components in the presence of a static magnetic field. It is caused by the interaction of the magnetic field with the magnetic moment of the atomic electron associated with ...

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

and of

iodine Iodine is a chemical element; it has symbol I and atomic number 53. The heaviest of the stable halogens, it exists at standard conditions as a semi-lustrous, non-metallic solid that melts to form a deep violet liquid at , and boils to a vi ...

) was directed by Eugène Bloch. From 1935 to 1946, Lacroute was an astronomer at the

Toulouse Observatory The Toulouse Observatory () is located in Toulouse, France and was established in 1733. It was founded by ''l'Académie des Sciences, Inscriptions et Belles-Lettres de Toulouse'' ("Academy of Science, Inscriptions and the Humanities of Toulouse") ...

where he set up an astrophysics department specializing in spectroscopic observation of stars. From 1946 until his retirement in 1976, he was a professor of astronomy at the Faculty of Sciences of Strasbourg and served as director of the

Observatory of Strasbourg The Observatory of Strasbourg is an astronomical observatory in Strasbourg, France. History This observatory is actually Strasbourg's third observatory: the first was built in 1673 on one of the city's surrounding towers (the astronomer Julius R ...

. He led the observatory's involvement in the AGK3R program. Since its creation in 1972 with the support of Jean Delhaye, then director of the National Institute of Astronomy and Geophysics, the observatory has housed the ''

Centre de Données astronomiques de Strasbourg Center or centre may refer to: Mathematics *Center (geometry), the middle of an object * Center (algebra), used in various contexts ** Center (group theory) ** Center (ring theory) * Graph center, the set of all vertices of minimum eccentric ...

'' (Strasbourg Astronomical Data Center), world database of astronomical knowledge.

Astrometry with artificial satellites

In the mid-1960s, Lacroute and Pierre Bacchus studied the problem of equipping a satellite with a telescope in order to overcome observational problems caused by planet Earth's atmosphere. In 1967, Pierre Lacroute proposed to the ''Centre national d'études spatiales'' (CNES, National Centre for Space Studies), to equip an

artificial satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scienti ...

with a

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

in order to obtain a

star catalogue A star catalogue is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the year ...

more accurate than could be established using terrestrial telescopes. The CNES agreed to develop the project but in view of its cost decided to move towards multinational financing. After a feasibility study carried out in 1977, the

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

finally agreed in 1980 to finance the mission. He was thus the initiator of the

satellite project launched by an Ariane IV rocket in 1989. The mission of this satellite was to measure the

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

es of stars.

Awards and honours

The

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

1851 Lacroute, discovered by Louis Boyer in 1950, is named in his honour. Lacroute was awarded in 1975

Prix Jules Janssen The Prix Jules Janssen is the highest award of the Société astronomique de France (SAF), the French astronomical society. This annual prize is given to a professional French astronomer or to an astronomer of another nationality in recognition ...

of the

Société astronomique de France The Société astronomique de France (SAF; ), the France, French astronomical society, is a non-profit association in the public interest organized under French law (Association loi de 1901). Founded by astronomer Camille Flammarion in 1887, its ...

and in 1992 the Prix André Lallemand of the

Académie des sciences The French Academy of Sciences (, ) is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific method, scientific research. It was at the forefron ...

. He was in 1986 the president of the

Académie des Sciences, Arts et Belles-Lettres de Dijon The Académie de Dijon was founded by Hector-Bernard Pouffier, the most senior member of the Parlement de Bourgogne, in 1725. It received royal ''lettres patentes'' in 1740. In 1775, it became the "Académie des Sciences, Arts et Belles-Lettres de ...

. A street in Dijon, his native city, is named in his honour.

Selected publications

* *

References

External links

* {{DEFAULTSORT:Lacroute, Pierre 1906 births 1993 deaths 20th-century French astronomers French astrophysicists École Normale Supérieure alumni University of Paris alumni