On Error Estimates for Hapke Photometric Model Parameters from Disk-integrated Phase Curves of Airless Planetary Bodies
The Hapke bidirectional reflectance model is widely used to analyze photometric observations of planetary surfaces. When fitting disk-integrated data, nonuniqueness concerns arise if observations lack sufficient phase angle coverage to constrain the model’s numerous parameters. Sparsity and nonunifo...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Planetary Science Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/PSJ/adcd5d |
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| Summary: | The Hapke bidirectional reflectance model is widely used to analyze photometric observations of planetary surfaces. When fitting disk-integrated data, nonuniqueness concerns arise if observations lack sufficient phase angle coverage to constrain the model’s numerous parameters. Sparsity and nonuniformity of observational phase angle coverage especially challenge the goal of obtaining reliable parameter values and error estimates. The obstacles include the relatively small number and phase angle spread of observations in comparison to the sizable number of model parameters, coupling of model parameters and their ability to mimic one another, and systematic differences in measurement uncertainties between data collected from different instruments and observing environments. In these cases, meaningful error analysis is especially critical. We lay a strategic foundation for obtaining uncertainty estimates for Hapke model parameters retrieved from fits to disk-integrated phase curves of airless planetary bodies. We develop and demonstrate analysis tools for treating the separate contributions of goodness-of-fit errors, uncertainties due to the absence of critical phase angle coverage, and absolute calibration errors. Our approach suggests a parameter retrieval methodology that leverages the intricate coupling among Hapke parameters to provide constraints that would not be possible were they strictly independent variables. We apply this new strategy to fits of the Hapke model to phase curves of Kuiper Belt objects and dwarf planets observed by New Horizons. |
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| ISSN: | 2632-3338 |