CORALIE

CORALIE
Name	CORALIE
Type	Echelle spectrograph
Location	La Silla Observatory
Operator	Observatoire de Genève and European Southern Observatory
Wavelength	Optical
Spectral resolution	~50,000
First light	1998
Mounted on	1.2-metre Leonard Euler Telescope
Country	Chile

CORALIE is a high-resolution optical echelle spectrograph installed on the 1.2-metre Leonard Euler Telescope at La Silla Observatory in Chile. Designed for precision radial-velocity measurements, it has been a workhorse for exoplanet detection and stellar astrophysics since first light in 1998. CORALIE's design heritage and operational model connect it to a lineage of instruments including predecessors and contemporaries at European Southern Observatory facilities and instruments developed by the Observatoire de Genève team.

Overview

CORALIE was commissioned to pursue programs at the intersection of observational programs led by teams at Observatoire de Genève, University of Geneva, European Southern Observatory, and collaborating institutions such as Max Planck Institute for Astronomy, University of California, Santa Cruz, and NASA. Its science drivers aligned with observational campaigns targeting targets from catalogs compiled by projects like Hipparcos and follow-up programs associated with surveys such as the Anglo-Australian Planet Search and Keck Planet Search. The instrument operates in the optical bandpass and emphasizes stability to measure Doppler shifts tied to programs similar to those of HARPS and HIRES.

Instrument Design and Components

CORALIE is an echelle spectrograph using a cross-dispersed design with a temperature-controlled bench. The optical train includes a collimator, an echelle grating, a cross-disperser, and a camera feeding a CCD detector comparable to sensors used in instruments at European Southern Observatory sites. The instrument couples to the telescope via a fibre link, a strategy employed by instruments at Observatoire de Genève and by teams at Anglo-Australian Observatory and Keck Observatory. The calibration subsystem features a Thorium-Argon lamp and simultaneous-reference fibres, methods shared with ELODIE and HARPS. The spectrograph enclosure incorporates vibration isolation informed by practices at Institut d'Astrophysique de Paris and Laboratoire d'Astrophysique de Marseille instrumentation groups. Thermal control and pressure stabilization mirror approaches developed for instruments at La Silla Observatory and Paranal Observatory.

Observing Modes and Performance

CORALIE supports high-precision radial-velocity mode using simultaneous wavelength calibration and single-fibre mode for fainter targets. Typical resolving power is around 50,000 with wavelength coverage optimized for stellar absorption lines used in Doppler work, paralleling strategies from ELODIE and SOPHIE. Long-term radial-velocity precision reached a few meters per second after upgrades, enabling detection of gas-giant exoplanets in short- and medium-period orbits similar to discoveries announced from California Planet Survey and Anglo-Australian Planet Search. Observing procedures and exposure-time calculators used by CORALIE teams are consistent with practices at European Southern Observatory and Observatoire de Genève observing programs.

Data Reduction and Calibration

Data reduction pipelines for CORALIE perform bias subtraction, flat-fielding, spectral order extraction, wavelength calibration, and radial-velocity determination via cross-correlation functions (CCF) with numerical masks. This approach reflects methods used by teams behind ELODIE, HARPS, and HIRES. Calibration uses Thorium-Argon spectra and simultaneous-reference fibre traces to track instrumental drift as in systems at European Southern Observatory and at La Silla Observatory. Reduced products feed into stellar parameter pipelines influenced by work at Geneva Observatory and databases maintained by collaborations with Centre de Données astronomiques de Strasbourg and survey teams associated with Hipparcos and Gaia follow-up efforts.

Scientific Contributions and Discoveries

CORALIE has contributed to the discovery and characterization of exoplanets, multiplicity studies, and stellar parameter surveys. Notable science outcomes include detection of gas-giant companions in programs coordinated with groups at Observatoire de Genève, confirmations of candidates from transit surveys such as OGLE follow-up campaigns, and radial-velocity monitoring that complemented photometric programs like SuperWASP and HATNet. CORALIE measurements have been cited in studies alongside results from HARPS, HIRES, UVES, and surveys by teams at Keck Observatory, Subaru Telescope, and Anglo-Australian Telescope. The instrument also supported stellar activity and rotation analyses in collaboration with researchers linked to Max Planck Institute for Astronomy and Institut d'Astrophysique de Paris.

Operation and Maintenance

Operational oversight of CORALIE is provided by teams from Observatoire de Genève in cooperation with staff at La Silla Observatory operated by European Southern Observatory. Routine maintenance includes fibre feed checks, CCD electronics servicing, thermal control verification, and calibration-lamp replacement following protocols similar to those at Paranal Observatory and Cerro Tololo Inter-American Observatory. Observing time allocation has been managed through time-allocation committees with institutional representation from University of Geneva, European Southern Observatory, and partner universities including University of Bern and Université de Haute-Savoie. Training and handover procedures draw on knowledge transfer practices used by instrument teams at European Southern Observatory and Observatoire de Genève.

Future Developments and Upgrades

Planned or proposed upgrades for instruments in this class, echoed in community discussions involving Observatoire de Genève, European Southern Observatory, and survey consortia such as Gaia follow-up groups, include detector replacement, improved thermal and pressure control, and enhanced calibration sources like laser frequency combs pioneered by collaborations involving MENLO Systems and research groups at Max Planck Institute for Quantum Optics. Synergies with next-generation surveys at ESO facilities and space missions like Gaia and TESS motivate continued modernization to maintain competitiveness with instruments such as HARPS-N and spectrographs on Very Large Telescope units.

Category:Astronomical spectrographs