In the course of the DR06 project a fitting routine was developed to correct spectra for telluric features (TFs) with the help of radiative transfer codes, meteorological data, and line databases. This approach was already successfully applied to a number of VLT instruments, e.g. CRIRES (Figure 1) and X-shooter (Figure 2). The previous project DR07 was aimed at improving the sky emission removal method developed by Davies (2007). Also this method was successfully applied to various VLT instruments, e.g. SINFONI and X-Shooter (see Figure 3 and Figure 4). The purpose of the SM-03 deliverable is twofold: It shall provide a sky signature correction tool which incorporates (a) an extension of the DR06 (fitting of radiance and transmission spectra) and the DR07 (sky emission subtraction) projects, and (b) an implementation of an improved telluric absorption feature correction procedure. In terms of code development SM-03 is closely related to SM-02, which aims at deriving atmospheric properties.
Figure 1: Best fit of an artificial transmission spectrum (red) to observed CRIRES data (black) performed with the DR06 software (see [6]). The gaps in the spectra (at ~3.295 µm, ~3.315µm, ~3.335µm) result from gaps between the CRIRES detector chips. In the artificial spectrum corresponding masks are used to exclude these regions in the fit. Note, that the transmission spectra are not normalised. (click to image to enlarge)
Figure 2: Same as in Figure 1, but for X-shooter(click to image to enlarge)
Figure 3: DR07 sky correction software applied on SINFONI J-band data (radiance units: photons/s m2 µm arcsec2). The upper panel shows the input and the best-fit sky spectrum. The lower panel gives the residual in two different scalings (black=original, green=optimal scaling)(click to image to enlarge)
Figure 4: DR07 sky correction software applied on X-Shooter data (radiance units: photons/s m2 µm arcsec). The upper panel shows the input and the best-fit sky spectrum. The lower panel gives the residual in two different scalings (black=original, green=optimal scaling)(click to image to enlarge)