Wavelength calibration from 1 - 5μm for the CRIRES+ high-resolution spectrograph at the VLT

Abstract

© 2014 SPIE.CRIRES at the VLT is one of the few adaptive optics enabled instruments that offer a resolving power of 105 from 1-5 μ m. An instrument upgrade (CRIRES+) is proposed to implement cross-dispersion capabilities, spectro-polarimetry modes, a new detector mosaic, and a new gas absorption cell. CRIRES+ will boost the simultaneous wavelength coverage of the current instrument (∼ λ/70 in a single-order) by a factor of ≳ 10 in the cross-dispersed configuration, while still retaining a 10 arcsec slit suitable for long-slit spectroscopy. CRIRES+ dramatically enhances the instrument's observing efficiency, and opens new scientific opportunities. These include high-precision radial-velocity studies on the 3m/s level to characterize extra-solar planets and their athmospheres, which demand for specialized, highly accurate wavelength calibration techniques. In this paper, we present a newly developed absorption gas-cell to enable high-precision wavelength calibration for CRIRES+. We also discuss the strategies and developments to cover the full operational spectral range (1-5 μ m), employing hollow-cathode emission lamps, Fabry-Pérotétalons, and absorption gas-cells.