The SARG Exo - Planets Search: The Instrument

The Spettrografo Alta Risoluzione Galileo (SARG)  is the high resolution optical spectrograph for the Italian  Telescopio Nazionale Galileo (TNG). Instrument characteristics include a high spectral resolution (maximum about R~150000), high efficiency (peak at about 13%), rather large spectral coverage in a single shot. SARG was designed as a multi-purpose instrument, in order to satisfy the scientific needs of a rather wide community. Emphasis in the design was put to have a high resolution, stable instrument, while not sacrificing efficiency; such an instrument is particularly suited for precise radial velocity programs, such as planet search and asteroseismology.

  To this purpose, SARG is equipped with an iodine cell (Marcy & Butler 1992, PASP 104, 270). The choice of the iodine cell technique is ideal for SARG, because it allows to achieve the best radial velocity precision maintaining at the same time the flexibility required by the multi-purpose nature of the instrument.