Volumetric Rendering of the Inner Coma of a Theoretically Modelled Comet for Comet Interceptor Mission

Abstract: The Comet Interceptor is a joint mission by European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) which seeks to perform a flyby over a Long Period Comet using a multi-element spacecraft. The Comet Interceptor comprises three spacecrafts- A, B1 and B2. All three spacecrafts will observe and map the comet at three different points on the coma of the comet, thereby making this mission the first ever multipoint mission dedicated to study a Long Period Comet. Out of the eleven instruments aboard the Comet Interceptor, the work done for this thesis aims to help the team designing the instrument-Optical Periscope Imager forComets (OPIC). The team designing OPIC uses the imaging simulation software Space Imaging Simulator for Proximity Operations (SISPO) to render images of theoretically modelled dust and gas densities of the coma of a comet to obtain prerequisite knowledge of the images which is to be taken by OPIC during its flyby. Using the theoretical model of the coma, a 3D model was created as part of the thesis which shall be later implemented in SISPO. The structure of the coma was made with the help of a sparse volumetric data manipulation tool OpenVDB, which was coded and run in Python. The generated data was imported in Blender to visualise the volumetric data with the help of Blender’s rendering engine-Cycles. To visualise the 3D model with utmost physical realism as the software Blender allows, a study on the scattering properties of the dust and gas model was done. Also, a motion blur was implemented in Blender to simulate the high relative velocity between the instrument and comet. Multiple approaches of varying complexities and time consumption were considered for importing and visualising the volumetric data. The final render images were brightness-matched with reference to images from previous cometary missions. Finally, a qualitative analysis was done by visually comparing the render images to the images from previous missions. With the help of this qualitative analysis, several features and characteristics were identified which were analogous to the real life images, thus establishing the correctness of the renders produced.