ELODIE spectrograph

ELODIE is a high-resolution spectrograph installed at the Observatoire de Haute-Provence 1.93-m reflector in south-eastern France. Its optical instrumentation was developed by André Baranne from the Marseille Observatory. This spectrograph is capable of detecting with an uncanny precision any small shift of a star, caused by the gravitational pull of an exoplanet.

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Michel Mayor and Didier Queloz discovered the first extrasolar planet 51 Pegasi b in 1995 using this instrument. Over twenty such planets have been found so far with ELODIE. First light was achieved in mid-1993 and it will continue to operate until the end of 2006, to be replaced by SOPHIE, a new instrument of the same type but with much improved features.

Characteristics

Spectra cover the 3895-6815 Å wavelength range in a single exposure, split into 67 orders. The instrument, which is located in a temperature-controlled room, is fed with optical fibers from the Cassegrain focus. One of the unique features of ELODIE is an integrated data reduction pipeline which fully reduces the spectra immediately after acquisition and allows the user to measure highly accurate radial velocities through cross-correlation with a numerical mask. This accuracy can reach ±7 m/s.

Over 30,000 spectra have been taken with this instrument so far, and about one-half are publicly available through a dedicated on-line archive. ELODIE is the result of a collaboration the observatories of Haute-Provence, Geneva and Marseille. A publication describing the instrument appeared in Astronomy & Astrophysics Supplements.

References

• ELODIE: A spectrograph for accurate radial velocity measurements