¹Philip R. Christensen,²Victoria E. Hamilton,¹Saadat Anwar,¹Greg Mehall,²John R. Spencer,³Jessica M. Sunshine,²Harold F. Levison
Journal of Geophysical Research (Planets) Open Access Link to Article [https://doi.org/10.1029/2024JE008493]
¹School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA
²Southwest Research Institute, Boulder, CO, USA
³University of Maryland, College Park, MD, USA
Published by arrangement with John Wiley & Sons

The Lucy Thermal Emission Spectrometer (L’TES) instrument acquired hyperspectral thermal infrared (TIR) observations of the Earth’s Moon during Lucy’s 2022 Earth gravity assist. L’TES covers the spectral range of 100–1,750 cm−1 (100–5.8 μm) at a spectral sampling of 8.64 cm−1 (Christensen et al., 2023, https://doi.org/10.1007/s11214-023-01029-y). The field of view (FOV) is 7.3-mrad, giving a spatial resolution on the Moon of 1,650 km. Seventeen high-quality spectra of the warm disk were acquired of Oceanus Procellarum that provide the first well-calibrated TIR observations of the Moon with high spectral resolution. The lunar surface emissivity was determined by modeling the surface radiance using two different methods that gave nearly identical results. The L’TES spectra have Christiansen feature (CF) maxima at 1,226 cm−1 (8.15 μm), a spectral band depth of ∼0.04, and a downward slope at wavenumbers >1,200 cm−1 that is characteristic of <100 μm particles. Comparison with Diviner 3-point spectral data (Greenhagen et al., 2010, https://doi.org/10.1126/science.1192196) shows excellent agreement in the CF location and band shape. The L’TES spectra closely match several lunar soil laboratory spectra (Donaldson-Hanna et al., 2017, https://doi.org/10.1016/j.icarus.2016.05.034), providing excellent ground truth for the L’TES observations, validating the L’TES data processing, and demonstrating that high-spatial and spectral resolution TIR data would provide a powerful tool for remote compositional mapping. The L’TES nightside observations accurately derived surface temperatures at 110 K, even when the Moon only filled 10% of the FOV, confirming that L’TES will accurately determine the cold Trojan asteroid temperatures.

¹Edwin S. Kite,²Benjamin M. Tutolo,¹Madison L. Turner,³Heather B. Franz,³David G. Burtt,⁴Thomas F. Bristow,⁵Woodward W. Fischer,⁶Ralph E. Milliken,⁷Abigail A. Fraeman,¹Daniel Y. Zhou
Nature 643, 60-66. Open Access Link to Article [DOI https://doi.org/10.1038/s41586-025-09161-1]
¹University of Chicago, Chicago, IL, USA
²University of Calgary, Calgary, Alberta, Canada
³NASA Goddard Space Flight Center, Greenbelt, MD, USA
⁴NASA Ames Research Center, Moffett Field, CA, USA
⁵California Institute of Technology, Pasadena, CA, USA
⁶Brown University, Providence, RI, USA
⁷Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

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