A passive cost-effective solution for the high accuracy wavelength calibration of radial velocity spectrographs

Abstract

Today, the RV technique has pushed the planet detection limits down to super-earths but the reach the precision required to detect earth-like planets it is necessary to reach a precision around 1cm s -1 . While a significant part of the error budget is the incompressible photon noise, another part is the noise in the wavelength calibration of the spectrograph. In the past 3 years the Observatory of Geneva has designed, built and tested an commissioned 2 wavelength calibrator systems based on a Fabry-Perot (FP) interferometer with great success. The calibrator system demonstrated 10 cm s -1 stability over one night and 1 m s -1 over 60 days. By improving the system injecting the calibration light into the calibration fiber of the spectrograph we are aiming at 1 m s -1 repeatability over the long term. This technique is now being extended to cover the near infrared to the K band in the frame of the SPIROU project.