Night-sky emission correction techniques for high-resolution spectroscopy: Demonstration with NIRPS
Abstract
Ground-based spectrographs operating in the near-infrared (NIR) regime are hampered by various absorption and emission features of Earth's atmosphere. While considerable attention has been paid to mitigating telluric absorption, correcting telluric emission features remains non-trivial and can significantly affect the observation of faint targets. We aim to develop and implement automated algorithms for sky background emission correction in the context of high-resolution spectroscopy. These empirical-based algorithms have been officially integrated into both NIRPS data reduction pipelines: NIRPS DRS and APERO DRS. Designed for flexibility, these techniques can be incorporated into the reduction workflow of any high-resolution spectrograph to improve the radial velocity (RV) performance. In our approach, a reference sky spectrum is first created by deep-stacking NIRPS sky calibration frames on a common wavelength grid and calculating the weighted median flux per pixel, separately for both the high-accuracy and high-efficiency instrument modes. This process is repeated for all spectral orders and for both the object and sky-calibration fibres: fibre A and fibre B, respectively. In this reference sky spectrum, the sky emission lines can be identified and used to construct a static library. During the data reduction process, the emission features in the library are individually scaled in terms of flux using two distinct techniques, each specific to the two DRS pipelines. Finally, they are locally subtracted from the science observations to minimise their noise contribution to the final spectrum. We find that the correction algorithms significantly improve the RV measurements obtained using both the cross-correlation function and line-by-line techniques, enabling NIRPS to achieve submetre-per-second precision in the NIR. The techniques have been successfully validated and demonstrated.
Versions
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BibTeX
@misc{srivastava2026nightsky,
title = {{Night-sky emission correction techniques for high-resolution spectroscopy: Demonstration with NIRPS}},
author = {Avidaan Srivastava and François Bouchy and Xavier Dumusque and Étienne Artigau and René Doyon and Neil J. Cook and Danuta Sosnowska and Flavie Bélanger and David Lafrenière and Frédérique Baron and Lison Malo and Susana C. C. Barros and Björn Benneke and Xavier Bonfils and Marta Bryan and Ryan Cloutier and Nicolas B. Cowan and Elisa Delgado-Mena and Xavier Delfosse and David Ehrenreich and Pedro Figueira and Jonay I. González Hernández and Izan de Castro Leão and Christophe Lovis and Bruno L. Canto Martins and Lucile Mignon and Christoph Mordasini and Francesco Pepe and Rafael Rebolo and Jason Rowe and Nuno C. Santos and Damien Ségransan and Alejandro Suárez Mascareño and Jose Renan De Medeiros and Stéphane Udry and Diana Valencia and Gregg Wade and Romain Allart and Vincent Bourrier and Pedro Branco and Charles Cadieux and Gaspare Lo Curto and Yolanda G. C. Frensch and Jonathan Gagné and Roseane de Lima Gomes and Nicole Gromek and Vigneshwaran Krishnamurthy and Pierrot Lamontagne and Yuri S. Messias and Khaled Al Moulla and Dany Mounzer and Nicola Nari and Léna Parc and Atanas K. Stefanov and Thomas Vandal and Drew Weisserman and Joost P. Wardenier},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03374},
eprint = {2609.03374},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03374},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Night-sky emission correction techniques for high-resolution spectroscopy: Demonstration with NIRPS
AU - Avidaan Srivastava
AU - François Bouchy
AU - Xavier Dumusque
AU - Étienne Artigau
AU - René Doyon
AU - Neil J. Cook
AU - Danuta Sosnowska
AU - Flavie Bélanger
AU - David Lafrenière
AU - Frédérique Baron
AU - Lison Malo
AU - Susana C. C. Barros
AU - Björn Benneke
AU - Xavier Bonfils
AU - Marta Bryan
AU - Ryan Cloutier
AU - Nicolas B. Cowan
AU - Elisa Delgado-Mena
AU - Xavier Delfosse
AU - David Ehrenreich
AU - Pedro Figueira
AU - Jonay I. González Hernández
AU - Izan de Castro Leão
AU - Christophe Lovis
AU - Bruno L. Canto Martins
AU - Lucile Mignon
AU - Christoph Mordasini
AU - Francesco Pepe
AU - Rafael Rebolo
AU - Jason Rowe
AU - Nuno C. Santos
AU - Damien Ségransan
AU - Alejandro Suárez Mascareño
AU - Jose Renan De Medeiros
AU - Stéphane Udry
AU - Diana Valencia
AU - Gregg Wade
AU - Romain Allart
AU - Vincent Bourrier
AU - Pedro Branco
AU - Charles Cadieux
AU - Gaspare Lo Curto
AU - Yolanda G. C. Frensch
AU - Jonathan Gagné
AU - Roseane de Lima Gomes
AU - Nicole Gromek
AU - Vigneshwaran Krishnamurthy
AU - Pierrot Lamontagne
AU - Yuri S. Messias
AU - Khaled Al Moulla
AU - Dany Mounzer
AU - Nicola Nari
AU - Léna Parc
AU - Atanas K. Stefanov
AU - Thomas Vandal
AU - Drew Weisserman
AU - Joost P. Wardenier
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03374
UR - https://arxiv.org/abs/2609.03374
AB - Ground-based spectrographs operating in the near-infrared (NIR) regime are hampered by various absorption and emission features of Earth's atmosphere. While considerable attention has been paid to mitigating telluric absorption, correcting telluric emission features remains non-trivial and can significantly affect the observation of faint targets. We aim to develop and implement automated algorithms for sky background emission correction in the context of high-resolution spectroscopy. These empirical-based algorithms have been officially integrated into both NIRPS data reduction pipelines: NIRPS DRS and APERO DRS. Designed for flexibility, these techniques can be incorporated into the reduction workflow of any high-resolution spectrograph to improve the radial velocity (RV) performance. In our approach, a reference sky spectrum is first created by deep-stacking NIRPS sky calibration frames on a common wavelength grid and calculating the weighted median flux per pixel, separately for both the high-accuracy and high-efficiency instrument modes. This process is repeated for all spectral orders and for both the object and sky-calibration fibres: fibre A and fibre B, respectively. In this reference sky spectrum, the sky emission lines can be identified and used to construct a static library. During the data reduction process, the emission features in the library are individually scaled in terms of flux using two distinct techniques, each specific to the two DRS pipelines. Finally, they are locally subtracted from the science observations to minimise their noise contribution to the final spectrum. We find that the correction algorithms significantly improve the RV measurements obtained using both the cross-correlation function and line-by-line techniques, enabling NIRPS to achieve submetre-per-second precision in the NIR. The techniques have been successfully validated and demonstrated.
ER -