IOT Overview: High Resolution Spectrographs
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ESO, Alonso de Cord´ ova 3107, Vitacura, Santiago, Chile; [email protected] Observatoire de Paris-Meudon, GEPI, 92195 Meudon Cedex, France
1 Introduction ESO operates a suite of nine High Resolution (HR) spectrographs in Chile, covering the wavelength range from the optical to the medium infrared. They explore a wide spectra of scientific goals, which ultimately define their specific characteristics. All the spectrographs are operated both in service and in visitor mode, and obey a similar operation scheme in common with all the ESO instruments, which is driven by the concept of Observation Blocks (OB), that allows users to entirely pre-define the instrument configuration for their observations. Calibrations, which are also used in part to monitor the instruments performance, are executed following dedicated calibration plans, presented in the instrument user manuals and web pages. This work is organized as follows: Section 2 presents a summary of the instrumentation, Section 3 discusses the main common calibration issues, Section 4 presents the issue of stability for instruments that are used in Radial Velocity (RV) measurements, and the last section presents some future prospects and the conclusions.
2 Instrumentation The ESO instrumentation for high resolution spectroscopy covers a wide range of formats and wavelengths. The suite of instruments includes both fibre and slit spectrographs, in fixed configuration or with tunable central wavelength. All the ESO high resolution spectrographs use echelle reflective diffraction gratings, either in pre-dispersed or in cross-dispersed format, for high dispersion and optimum efficiency. As always, the accent has been put on providing high data quality and efficiency: technical downtime due to the spectrographs is generally well below 2%. This is achieved through the execution of well aimed maintenance plans. The science coverage of the ESO high resolution spectrographs is extremely large, ranging from solar system to extra-galactic astrophysics. In the years 2005 and 2006 the ESO high resolution spectrographs alone have contributed to more than 300 refereed publications.
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G. Lo Curto et al.
Apart from CES and EMMI-echelle, which only have “quick-look” scripts, all ESO high resolution spectrographs are equipped with online pipelines, which, apart from performing the reduction of the data, supply the basic quality control parameters. The HARPS pipeline is developed and maintained by the consortium who build the instrument, and besides delivering science products and precise radial velocities also performs online quality control. 2.1 Optical Spectrographs Fibre-Fed, Extended Range, Echelle Spectrograph (FEROS) The FEROS spectrograph [10] is a fibre fed, cross dispersed echelle spectrograph. It uses two fibres whose diameter covers an angle of 2” in the sky, one fibre is normally placed on the science target while the other one can be exposed either to the empty sky for background subtraction or to a reference light for drift measurement and optimum radial velocity precision. The confi
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