vipere - Telluric correction for CRIRES+ spectra

Forked and adapted from viper by Zechmeister & Koehler. Simplified to a single-file tool focused on telluric removal and stellar template creation for CRIRES+ data.

Author: Alexis Lavail (with help from Claude)

Requirements

• Python >= 3.10
• astropy, matplotlib, numpy, scipy

Installation

Install as a global command with uv:

uv tool install -e /path/to/vipere

The -e (editable) flag means changes to the code take effect immediately without reinstalling. You can then run vipere from anywhere on your system.

Updating

If installed with -e (editable), just pull the latest version:

cd /path/to/vipere && git pull

Changes take effect immediately — no reinstall needed.

If installed without -e, reinstall after pulling:

cd /path/to/vipere && git pull
uv tool install -e . --force

Usage

vipere "data/WASP18/cr2res*.fits" \
  -createtpl -telluric add -tsig 10 -tpl_wave tell \
  -deg_norm 2 -deg_wave 2 -o data/WASP18/tpl1

Alternatively, run directly without installing:

uv run vipere.py "data/WASP18/cr2res*.fits" -createtpl -telluric add -o output

See vipere -? for all options.

Key flags

Flag	Description	Default
-o	Output basename for result files	tmp
-oset	Order index range (e.g. 1:22 for 21 orders); auto-detected from FITS if omitted	auto
-nset	Spectrum index range	: (all)
-createtpl	Create a stellar template from multiple observations	off
-telluric	Telluric mode: add (per-molecule coefficients) or add2 (combined non-water coefficient)	off
-global_atm	Fit atmosphere globally across all orders (shared RV + atm coefficients)	off
-wavecorr_2d	Interpolate wavelength solution for unfitted orders via 2D polynomial fit per chip	off
-tellshift	Allow a wavelength shift of the telluric model	off
-tell_bic	BIC threshold for telluric model selection (0 to disable)	10
-tsig	Relative sigma for weighting telluric regions	1
-tpl_wave	Output wavelength grid: initial, berv, or tell	initial
-tpl_noRV	Do not apply stellar RV shift to telluric-corrected spectrum (with -createtpl)	off
-deg_norm	Polynomial degree for flux normalisation	3
-deg_wave	Polynomial degree for wavelength solution	3
-deg_bkg	Polynomial degree for background model	0
-oversampling	Oversampling factor for the template	auto
-ip	IP model: g, ag, sg, bg, mg, mcg	g
-kapsig	Kappa-sigma clipping values per stage (0 = no clipping)	0
-kapsig_ctpl	Kappa-sigma for outlier clipping in template creation	0.6
-plot	Plot level: 0 = off, 1 = with pause, 2 = without pause (saves PNG)	0
-rv_guess	Initial RV guess [km/s]	1.0
-vcut	Trim observation to range valid for model [km/s]	100
-fix	Fix parameters (e.g. -fix wave for stabilised instruments)	none
-molec	Molecules to include (all for automatic selection)	all
-nexcl	Ignore spectra matching string pattern	none
-wgt	Weighted fit: error (use data errors) or tell (upweight tellurics)	off
-config_file	YAML config file to override defaults	none

Citation

If you use this tool, please cite the original viper pipeline: https://ui.adsabs.harvard.edu/abs/2021ascl.soft08006Z