Whole-disk Photometric and Colorimetric Phase Curves of Earth with the Clementine Lunar Orbiter
Abstract
The phase curve on a planetary object can reveal key details about its atmosphere and surface, including the presence of surface liquid oceans. Phase curves for Earth can inform the search for habitable surface environments on terrestrial exoplanets, but such phase curves are quite rare. The Clementine lunar orbiter made 3,744 observations of the Earth between February and May of 1994. These observations spanned phase angles between 3.4 and 139.1 degrees. From these data, we produce phase curves of Earth in 5 distinct bands with wavelengths between 400 nm and 1000 nm. We extrapolate fits to the phase curves to derive the geometric albedo of Earth in each filter. We examine the Earth's color as a function of phase angle and find the observed values are best fitted by models that include contributions from ocean glint. We also find a number of observations where contributions from glint are minimal but the disk-integrated color is in line with the glinting model predictions; we propose that this can be explained by the presence of optically clouds on the disk. These findings stress the importance of high-phase Earth observations for high-fidelity Earth models and for future efforts to characterize terrestrial exoplanets via direct imaging.
Related
- Connectivity rewiring and filament formation by active region emergence observed with Solar Orbiter
- Connectivity rewiring and filament formation by active region emergence observed with Solar Orbiter
- Current Sheets and Magnetic Reconnection statistics by Solar Orbiter at few to tens of Ion Inertial Lengths II: Conditions for Reconnection, and Current Sheet Planarity
- Radial Evolution of Turbulent Modes near the Sun Using Parker Solar Probe and Solar Orbiter Measurements
- Successfully Reproducing Solar Orbiter Polar Field Observations with a Surface Flux Transport Model
BibTeX
@misc{cooper2026wholedisk,
title = {{Whole-disk Photometric and Colorimetric Phase Curves of Earth with the Clementine Lunar Orbiter}},
author = {Chase Cooper and Tyler D. Robinson and L. C. Mayorga and Jason W. Barnes and Lily Robinthal},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.36291},
eprint = {2609.36291},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.36291},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Whole-disk Photometric and Colorimetric Phase Curves of Earth with the Clementine Lunar Orbiter
AU - Chase Cooper
AU - Tyler D. Robinson
AU - L. C. Mayorga
AU - Jason W. Barnes
AU - Lily Robinthal
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.36291
UR - https://arxiv.org/abs/2609.36291
AB - The phase curve on a planetary object can reveal key details about its atmosphere and surface, including the presence of surface liquid oceans. Phase curves for Earth can inform the search for habitable surface environments on terrestrial exoplanets, but such phase curves are quite rare. The Clementine lunar orbiter made 3,744 observations of the Earth between February and May of 1994. These observations spanned phase angles between 3.4 and 139.1 degrees. From these data, we produce phase curves of Earth in 5 distinct bands with wavelengths between 400 nm and 1000 nm. We extrapolate fits to the phase curves to derive the geometric albedo of Earth in each filter. We examine the Earth's color as a function of phase angle and find the observed values are best fitted by models that include contributions from ocean glint. We also find a number of observations where contributions from glint are minimal but the disk-integrated color is in line with the glinting model predictions; we propose that this can be explained by the presence of optically clouds on the disk. These findings stress the importance of high-phase Earth observations for high-fidelity Earth models and for future efforts to characterize terrestrial exoplanets via direct imaging.
ER -