Wavelength calibrators are a critical component of high precision and accuracy radial velocity measurements. An order of magnitude improvement of the state-of-the-art of calibration of echelle spectrographs is amongst the requirements needed to achieve detection of earth-mass planets around sun-like stars in the habitable zone. We present studies of calibrators using a custom Fourier Transform Spectrograph (FTS) optimized for characterizing broadband, high repetition-rate laser frequency combs ("astro-combs") as well as other calibration sources including Th:Ar lamps and white-light etalons.
