HARPS: a new high-resolution spectrograph for the search of extrasolar planets

HARPS is a high-resolution spectrograph dedicated to the search for extra-solar planets by means of precise radial- velocity measurements. It will be installed on the ESO 3.6-m telescope at the ESO La Silla observatory and should start its operation son end 2002. The observations will provides for many solar-type stars of the solar vicinity a high number of RV measurements with 1 ms -1 accuracy and will allow the detection of Saturn-like planets. The instrument is a fiber-fed and cross-dispersed echelle spectrograph. It has been designed and optimized to measure the Doppler shift of the stellar spectrum by means of cross correction of the spectrum with a numerical mask. For this purpose the entire spectrum in the wavelength range from 380 nm to 680 nm is imaged on a 4k4 mosaic CCD detector at a spectral resolution of about R equals 90,000. Wavelength calibration is provided by a ThAr lamp simultaneously imaged on the CCD. The HARPS spectrograph is also characterized by its high optical efficiency and the high thermo-mechanical stability. Indeed the whole instrument will be temperature controlled and operated in vacuum, in order to assure its short and long-term stability. This paper summarizes the present status of the project and describes the optical and instrument design of HARPS. Also a short presentation of the scientific objectives pursued with HARPS is given by the author.