The Danish 1.54-metre telescope at La Silla

The CORrelation-RAdial-VELocities (CORAVEL) instrument was a Cassegrain spectrometer for determining stellar radial velocities with very high time resolution and high accuracy. The instrument was mounted on the Danish 1.54-metre telescope at La Silla Observatory in 1981 and was operated by the Geneva Observatory and then shared with Danish and ESO astronomers. CORAVEL was mounted on the Danish 1.54-metre telescope because it required a rather large telescope (1.5 metre diameter or larger), allowing fast automatic pointing and this telescope was the only one adapted to receive it.

The project for building CORAVEL started in 1972 from a collaboration between the Marseille Observatory and the Geneva Observatory and was financed by the Swiss National Foundation for Scientific Research and the French National Institute for Astrophysics and Geophysics. Two CORAVEL instruments were made, the first being mounted on the 1-metre Swiss telescope at the Haute-Provence Observatory in 1977. With the second CORAVEL mounted on the Danish 1.54-metre telescope a natural collaboration between ESO astronomers and astronomers from several institutes and observatories in Denmark, Switzerland and France was born.

As a radial velocity scanner, CORAVEL worked by comparing a stellar spectrum with a reference spectrum, providing for that period exceptional accuracy (1800 km/h) and acquisition speed (measurements took less than 5 minutes). The reference was a plaque with about 3000 holes matching the absorption lines of Arcturus and that was located in the focal plane of the spectrograph. The radial velocity of the stars under study was calculated by measuring the spectral shift of their absorption lines relative to Arcturus’ lines.

During their more than 20 years of operation the two CORAVEL spectrometers measured hundreds of thousands of  radial velocities in thousands of stars, most of them part of surveys conducted in Chile and France. These surveys included that of Milky Way classical Cepheid stars[1], giant Ba and S stars[2a,b] or late-type stars[3] of the Hipparcos mission.

CORAVEL in La Silla was decommissioned in January 1998 and eventually returned to Switzerland.


This table lists the global capabilities of the instrument. The authoritative technical specifications as offered for astronomical observations are available from the Science Operations page.

Location: Decommissioned
Telescope: Danish 1.54-m telescope
Focus: Cassegrain
Type: Spectrometer
Wavelength range: 360–520 nm
Spatial resolution:
Spectral resolution: R ~20 000
First light: January 1981
Science goal:
  • Stellar radial velocities
  • Stellar rotation
  • Stellar metallicity
Images taken with the instrument: Link
Images of the instrument: Link
Press Releases with the instrument: Link
  • Observatoire de Marseille
  • Observatoire de Genève
  • Copenhagen University Observatory
  • ESO