Broadband near-infrared astronomical spectrometer calibration and on-sky validation with an electro-optic laser frequency comb

• Published in: Optics express Vol. 26; no. 26; pp. 34830 - 34841
• Main Authors: Obrzud, E, Rainer, M, Harutyunyan, A, Chazelas, B, Cecconi, M, Ghedina, A, Molinari, E, Kundermann, S, Lecomte, S, Pepe, F, Wildi, F, Bouchy, F, Herr, T
• Format: Journal Article
• Language: English
• Published: United States 24-12-2018
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.26.034830

The quest for extrasolar planets and their characterization as well as studies of fundamental physics on cosmological scales rely on capabilities of high-resolution astronomical spectroscopy. A central requirement is a precise wavelength calibration of astronomical spectrographs allowing for extraction of subtle wavelength shifts from the spectra of stars and quasars. Here, we present an all-fiber, 400 nm wide near-infrared frequency comb based on electro-optic modulation with 14.5 GHz comb line spacing. Tests on the high-resolution, near-infrared spectrometer GIANO-B show a photon-noise limited calibration precision of < 10 cms as required for Earth-like planet detection. Moreover, the presented comb provides detailed insight into particularities of the spectrograph such as detector inhomogeneities and differential spectrograph drifts. The system is validated in on-sky observations of a radial velocity standard star (HD221354) and telluric atmospheric absorption features. The advantages of the system include simplicity, robustness and turn-key operation, features that are valuable at the observation sites.