NASA GODDARD INSTITUTE FOR SPACE STUDIES
Radiative-Transfer Modeling of Spectra of Planetary Regoliths
“Remote sensing observations of Solar System bodies can be beneficial in inferring important properties of a given planetary surface. However, proper interpretation of remote sensing datasets can be difficult, especially for surfaces that are covered with regolith—fine-grained particles frequently resulting from various weathering events (e.g., meteor bombardments). Radiative transfer theory has often been applied to the study of densely packed particulate media like regoliths, but with difficulty. Here, we continue to investigate radiative transfer modeling of spectra of densely packed particulate media that may be appropriate for regoliths.”
Findings and Results
“The incorporation of the near-field effects with superposition T-matrix method and dense packing correction with static structure factor can better reproduce spectra of densely packed particulate media like planetary regoliths.
We use the superposition T-matrix method to compute scattering properties of clusters of particles and capture the near-field effects important for dense packing. Then these scattering parameters are modified with static structure factor correction, accounting for the dense packing of the clusters themselves. Using these corrected scattering parameters, reflectance (or emissivity via Kirchhoff’s Law) is computed with the method of invariance imbedding solution to the radiative transfer equation. Emissivity spectrum of enstatite in 3.3 μm particle size fraction, representing some common components of regoliths, in the mid-infrared wavelengths (5 – 50 m) was modeled. Spectrum from the T-matrix method with static structure factor correction using moderate packing densities (filling factors of 0.1 – 0.2) produced better fits to the laboratory measurement of corresponding spectrum than the spectrum modeled by the equivalent method without static structure factor correction. Future works will test the method of the superposition T-matrix and static structure factor correction combination for larger particles sizes and polydispersed clusters in search for most effective modeling of spectra of planetary regoliths.”
“The internship helped me refresh my knowledge in Fortran programming and mathematical theorems. I attended a seminar on aerosols and multiple enrichment trips to various locations in New York City. Overall, it was an excellent experience. My mentor and internship coordinators were supportive, and the content of the work was on-the-spot with my interests in the subjects of light scattering and radiative transfer. The internship reinforced my career plan to become a formal NASA scientist.
“Publications I was involved in included an abstract submission to American Geophysical Union Fall Meeting and a chapter of a PhD dissertation. I also wrote the dense packing Fortran program.”