NASA’s Pandora SmallSat Mission: Simulating the Impact of Stellar Photospheric Heterogeneity and Its Correction

Abstract Stellar photospheric heterogeneity is a dominant astrophysical systematic impacting exoplanet transmission spectroscopy. NASA’s Pandora SmallSat Mission is designed to address this challenge through contemporaneous visible-band photometry and near-infrared spectroscopy of exoplanet host stars. Here, we present an end-to-end simulation study quantifying Pandora’s ability to infer stellar photospheric properties and correct stellar contamination using out-of-transit observations. We construct eight representative stellar activity scenarios and generate 160 simulated Pandora datasets, incorporating time-dependent stellar spectra, instrument response, and noise. Given accurate models, Bayesian retrievals of joint visible photometry (0.4–0.7 μ m) and near-infrared spectroscopy (0.9–1.6 μ m, R ≈ 120) recover photospheric temperatures with typical uncertainties of ≈30 K, with no significant bias. Models with two spectral components (i.e., a quiescent photosphere and spots) are strongly favored in 95% of cases; one-component models are preferred when true spot filling factors fall below a detection threshold of ≈0.3%. We propagate the true and inferred stellar parameters to compute true, inferred, and residual contamination signals under physically motivated spot geometries. For simple spot distributions, contamination signals of 10 2 –10 3 ppm are reduced to ≲10 ppm—well below Pandora’s expected transmission spectroscopy precision (30–100 ppm). For more complex spot distributions, geometric degeneracies limit deterministic corrections, leaving residual contamination at the 10 3 ppm level that must be mitigated using additional constraints, such as spot-crossing events and joint stellar–planetary retrievals of transmission spectra. These results define regimes in which stellar contamination can be corrected from stellar observations alone and show how Pandora stellar observations can identify cases where additional information is required.

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Journal
The Astronomical Journal
Published
2026-05-08
DOI
https://doi.org/10.3847/1538-3881/ae5f63
Primary Topic
Stellar, planetary, and galactic studies
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article
Field-Weighted Citation Impact
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article

NASA’s Pandora SmallSat Mission: Simulating the Impact of Stellar Photospheric Heterogeneity and Its Correction

Joshua E. Schlieder, Pete Supsinskas, Trevor O. Foote, Brett M. Morris et al.
The Astronomical Journal
Stellar, planetary, and galactic studies
article

NASA’s Pandora SmallSat Mission: Simulating the Impact of Stellar Photospheric Heterogeneity and Its Correction

Joshua E. Schlieder, Pete Supsinskas, Trevor O. Foote, Brett M. Morris, Nikole K. Lewis, Susan E. Mullally, Emily A. Gilbert, Veselin B. Kostov, Jessie Dotson, Thomas P. Greene, Aurora Y. Kesseli, Knicole D. Colón, Jessie L. Christiansen, Peter McGill, A. Youngblood, Kelsey Hoffman, Jordan Karburn, Thomas Barclay, Jason Rowe, B V Rackham, Megan Weiner Mansfield, James P. Mason, Aishwarya R. Iyer, Christina Hedges, Luis Welbanks, Dániel Apai, Gregory Mosby, Yoav Rotman, Elisa V. Quintana, David R. Ciardi, Rae Holcomb
article en

Abstract

Abstract Stellar photospheric heterogeneity is a dominant astrophysical systematic impacting exoplanet transmission spectroscopy. NASA’s Pandora SmallSat Mission is designed to address this challenge through contemporaneous visible-band photometry and near-infrared spectroscopy of exoplanet host stars. Here, we present an end-to-end simulation study quantifying Pandora’s ability to infer stellar photospheric properties and correct stellar contamination using out-of-transit observations. We construct eight representative stellar activity scenarios and generate 160 simulated Pandora datasets, incorporating time-dependent stellar spectra, instrument response, and noise. Given accurate models, Bayesian retrievals of joint visible photometry (0.4–0.7 μ m) and near-infrared spectroscopy (0.9–1.6 μ m, R ≈ 120) recover photospheric temperatures with typical uncertainties of ≈30 K, with no significant bias. Models with two spectral components (i.e., a quiescent photosphere and spots) are strongly favored in 95% of cases; one-component models are preferred when true spot filling factors fall below a detection threshold of ≈0.3%. We propagate the true and inferred stellar parameters to compute true, inferred, and residual contamination signals under physically motivated spot geometries. For simple spot distributions, contamination signals of 10 2 –10 3 ppm are reduced to ≲10 ppm—well below Pandora’s expected transmission spectroscopy precision (30–100 ppm). For more complex spot distributions, geometric degeneracies limit deterministic corrections, leaving residual contamination at the 10 3 ppm level that must be mitigated using additional constraints, such as spot-crossing events and joint stellar–planetary retrievals of transmission spectra. These results define regimes in which stellar contamination can be corrected from stellar observations alone and show how Pandora stellar observations can identify cases where additional information is required.

The Astronomical JournalVol. 171(6)
Bishop's University (CA), California Institute of Technology (US), Ames Research Center (US), Lawrence Livermore National Laboratory (US), Space Telescope Science Institute (US), Space Science Institute (US), Goddard Space Flight Center (US), University of Arizona (US), Cornell University (US), NASA Exoplanet Science Institute (US), Johns Hopkins University Applied Physics Laboratory (US), Université Bourgogne Franche-Comté (FR), Arizona State University (US), Massachusetts Institute of Technology (US), University of Maryland, College Park (US), University of Maryland, Baltimore County (US), Search for Extraterrestrial Intelligence (US)
National Aeronautics and Space Administration, Heising-Simons Foundation
Openalex Percentile: Top 5%
Stellar, planetary, and galactic studies
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