New wavelength calibration of the HARPS spectrograph

Understand

(abridged) Even if the HARPS spectrograph has been operational for more than 15 years and it provides among the most precise Doppler measurements, improvements are still possible.

• One known problem, for instance, is the non-fully regular block-stitching of the CCDs, which introduces, in some cases, one-year period parasitic signals in the measured radial velocity.
• The aim is to improve the wavelength calibration of HARPS to push further its planet-detection capabilities.
• The properties of the CCD stitching-induced pixel-size anomalies are determined with LED flat-field frames, and then a physical, gap-corrected map of the CCDs is used for the fitting model of the spectral orders.