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Deriving the Thermophysical Properties of Planetary Surfaces Using Off-Axis Thermal Emission Spectroscopy

McKeeby, Benjamin E. (2023) Deriving the Thermophysical Properties of Planetary Surfaces Using Off-Axis Thermal Emission Spectroscopy. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Thermal mixing below the spatial resolution of thermal infrared (TIR) instruments can produce negatively sloped emissivity spectra at longer wavelengths that may inhibit accurate compositional analysis. Sloped spectra are produced either from an incorrect assumption of a uniform surface temperature or a maximum emissivity during temperature-emissivity separation of the radiance data. Surfaces viewed at higher solar incident angles and/or emission angles display greater varied amounts of sub-pixel anisothermality due to the viewing geometry. Spectral slopes are distinct, with magnitudes proportional to the degree of anisothermality.
Laboratory work utilizing hyperspectral TIR spectroscopy and high-definition 3D photogrammetry is also detailed to describe the effects of micro and macro surface roughness on the TIR spectrum. Micron scale roughness results in a reduction in spectral contrast due to multiple surface reflections by emitted radiant energy. This does not result in negative spectral slopes. However, rough surfaces are also prone to differential heating due to shelf shadowing. Where this is the case and anisothermality manifests at sub-pixel scale, spectral slopes can develop. By combining rigorous hyperspectral TIR spectroscopy with statistical surface topographic analysis we investigate these two thermophysical effects in natural basaltic surfaces, and under viewing conditions analogous to the THEMIS ROTO data.
Routine Off-nadir Targeted Observations (ROTO) of the Thermal Emission Imaging Spectrometer (THEMIS) are used here for the first time to validate prior surface roughness modeling that used nadir-only THEMIS data. Two regions within Apollinaris Mons and two regions within Arsia Mons are studied here using THEMIS ROTO data acquired near to or just after local sunset. Spectral slopes and brightness temperatures are modeled using thermal model to predict the lateral distribution of rock and dust, and the vertical thickness of dust layering. Ultimately, this method allows for determinations of particle size, rock abundance, and dust mantling. Additionally, it may assist with the separability of rock and dust spectral signatures necessary to perform rigorous compositional analysis.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
McKeeby, Benjamin E.bem101@pitt.edubem1010000-0003-2621-6152
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairRamsey, Michael S.mramsey@pitt.edumramsey0000-0001-8911-9187
Committee MemberHarbert,
Committee MemberBain,
Committee MemberShelef, Eitanshelef@pitt.edu0000-0003-0672-5144
Committee MemberHamilton, Victoriahamilton@boulder.swri.edu0000-0001-8675-2083
Date: 25 January 2023
Date Type: Publication
Defense Date: 19 July 2022
Approval Date: 25 January 2023
Submission Date: 9 September 2022
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 212
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Geology and Environmental Science
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Spectroscopy, Planetary Science, Mars Surface Processes
Date Deposited: 25 Jan 2023 20:56
Last Modified: 16 Feb 2023 21:45

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