Detailed Geometry Data Study and Photometric Analysis with Rosetta/OSIRIS Images of Comet 67P/Churyumov-Gerasimenko

The Rosetta mission greatly broadened our view of Comet surface after escorting Comet 67P/Churyumov-Gerasimenko for more than two years from 3.6 AU pre-perihelion to 3.3 AU post-perihelion. The rich set of imaging data at down to sub-meter scales returned by Rosetta OSIRIS Narrow Angle Camera (NAC) enables us to study surface changes on the nucleus of a Jupiter Family Comet at an unprecedented level of detail. Because photometric properties are sensitive to the physical properties of a surface, such as texture, porosity, roughness, and grain size, they can serve as markers for local alteration processes. With a high-resolution shape model, we investigate the physical properties of various locations on the surface of 67Ps nucleus at various perihelion distances through photometric analysis. We examine different regolith alteration and dust transportation scenarios in different geomorphological settings, and measure the properties with our best accurate methods. To achieve the best quality of photometric analysis and examine the subtle differences in the photometric properties across the surface, we used the United States Geological Surveys Integrated Software for Imagers and Spectrometers (ISIS). ISIS is used to photogrammetrically control (i.e., adjust spacecraft pointing and position of) the images and then derive the geometry data (x, y, z, incidence, emission and phase angle etc.) for all images. We will report our method to generate the geometry data and the preliminary results of our detailed photometric analysis for a few different geomorphological sites. Acknowledgments: This work is supported by NASA under Grants 80NSSC19K0421 and 80NSSC20K1152.