HARPS-N is an echelle spectrograph covering the wavelength range between 383 to 693 nm, with a spectral resolution R=115000. This instrument allows the measurement of radial velocities with the highest accuracy currently available in the north hemisphere and is designed to avoid spectral drift due to temperature and air pressure variations thanks to a very accurate control of pressure and temperature. HARPS-N is fibre-fed by the Nasmyth B Focus of the 3.6 TNG telescope through a Front End Unit (FEU). The two HARPS fibres (object + sky or Th-Ar) have an aperture on the sky of 1""; this produces a resolving power of 115,000 in the spectrograph. Both fibres are equipped with an image scrambler to provide a uniform spectrograph pupil illumination, independent of pointing decentering.
The main scientific rationale of HARPS-N is the characterization and discovery of terrestrial planets by combining transits and Doppler measurements.
The HARPS-N Project is a collaboration between the Astronomical Observatory of the Geneva University (lead), the CfA in Cambridge, the Universities of St. Andrews and Edinburgh, the Queens University of Belfast, and the TNG-INAF Observatory.