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

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Obrzud, Ewelina
Rainer, Monica
Harutyunyan, Avet
Chazelas, Bruno
Cecconi, Massimo
Ghedina, Adriano
Molinari, Emilio
Kundermann, Stefan
Lecomte, Steve
Pepe, Francesco
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.
Publication Reference
Optics Express, vol. 26 (26), pp. 34830-34841