RomainAllart / Telluric_correction

Automatic telluric correction for ESPRESSO and NIRPS ESO pipelines

Telluric correction

Automatic telluric correction for ESPRESSO and NIRPS ESO pipelines. This is a stand-alone Python script, described in detail in Allart et al. 2022 (ADS link: https://ui.adsabs.harvard.edu/abs/2022A%26A...666A.196A/abstract). Please cite this paper when using this code.

To summarize, the goal is to have an automatic code that is able to correct astrophysical spectra from the main absorber of the Earth's atmosphere. It consists of a radiative transfer model with one atmospheric layer. The produced telluric spectrum is convolved at the instrumental resolution and a least-square minimization is performed on carefully selected lines to optimize the parameters of the model. It is currently adapted to ESPRESSO and NIRPS but will be extended to other instruments in the near future.

The code is fully running on Python 3.9 and requires the following packages:

Users have to clone the repository to their personal directory and make sure that the following libraries are installed.

• numpy
• os
• astropy
• multiprocessing
• glob
• lmfit
• scpipy
• functools
• warning

Structure of the repository:

• The telluric_correction.py script contains all the functions to perform the telluric correction.
• The run_telluric_correction.py script is to run the telluric correction. Users only have to manipulate this file.
• The run_telluric_correction_for_Trigger.py is for internal consortium use.
• The Static_model directory containts fits files with line list parameters and the selection of lines to perform the optimization.
• The Static_resolution directory includes resolution maps for the different modes of NIRPS and ESPRESSO.

The following parameters can be modified in the run_telluric_correction.py:

• files_drs is an array of files for which the telluric correction as to be performed. It is important to only provide S2D_BLAZE_A.fits files to perform the telluric correction.
• instrument can either be 'ESPRESSO' or 'NIRPS_drs' for now. Functions in the telluric_correction.py take care of the different instrumental modes.
• molecules can either be ['H2O','O2'] or ['H2O,'O2','CO2','CH4'] respectively for ESPRESSO and NIRPS. These molecules are the main absorber in their respective spectral range.
• save_path is the output folder to save the data.
• save_options is an array that can contains either or all of the following keywords: 'DRS', 'Extended' and 'Telluric'.
  • 'DRS' creates a S2D_BLAZE_A_TELL_CORR.fits file where the spectrum is telluric corrected.
  • 'Extended' creates a S2D_BLAZE_A_TELL_CORR_EXTENDED.fits file that contains the uncorrected spectrum, the corrected spectrum, and the telluric spectrum.
  • 'Telluric' creates a S2D_BLAZE_A_TELL.fits file with the telluric spectrum alone.
  • As an additional note, the telluric corrected spectra are set to 0 when the telluric lines have an absorption larger than 90% to avoid numerical effect.
• By default, the telluric correction uses multiprocessing to split the files to correct on the number of cores available - 2.