Laser-tracked Fabry-Perot etalons as wavelength calibrators for high-precision Doppler spectroscopy

Exoplanet space missions like TESS and PLATO require extensive follow-up through radial-velocity measurements from ground-based telescopes equipped with high-precision Doppler spectrographs. Radial velocity measurements are needed to characterise the orbit and mass, and complete the picture of densities and composition of the exoplanet systems found. These instruments' key performance issue is the availability of a long-term stable wavelength calibration source. This project aims to develop an affordable wavelength calibration system to enable extreme precision radial-velocity observations on small and medium-size telescopes. The system is based on the regularly peaked transmission spectrum of a Fabry- Pérot etalon, locked to an atomic transition through laser spectroscopy to provide it with absolute accuracy. The first part of this project involves the design, construction and characterisation of the Fabry-Pérot unit, its integration with the locked reference laser, and its commissioning on the HERMES spectrograph of the Mercator telescope. Thereafter, we will demonstrate the calibration system's performance on a set of TESS exoplanet detections, using HERMES radial-velocity measurements to confirm these discoveries and measure the mass and density of the exoplanets.