VISUALIZING SPACE DATA IN VIRTUAL REALITY

Virtual reality is a useful and effective method to visualize space data in an immersive way. 3D models of space objects, such as asteroids and the Moon, can be implemented in VR using previously collected data and analyzed more efficiently. An immersive 3D space allows for many advantageous applications in scientific fields, exploration, training, and more. Introduction. Vast amounts of data can be gathered from imaging celestial bodies from an exploration spacecraft. These data can be used for a multitude of applications and are often used to construct 3D models of the observed body. There exists a variety of ways to display and interact with these models and the various scientific measurements that may be co-registered to this model (e.g., albedo, chemical composition, slope). Recent decades have seen great advancements in virtual reality (VR) technology that now allows the analyst to enjoy an immersive experience that often facilitates a greater understanding of the data. To explore this idea, we have created a computer graphics pipeline using the game engine Unreal Engine† to allow for exploration of the lunar surface using topography data derived from the Lunar Reconnaissance Orbiter Camera (LROC). Specifically, the example VR environment created here places the user on a digital elevation model (DEM) of the Moon’s TaurusLittrow Valley (which includes the Apollo 17 Landing site). Remarks on Potential Applications. Virtual reality has numerous applications in space science and exploration. A few potentially useful and interesting topics are briefly discussed here. Analysts may use VR to immersively explore data. In some cases, such an immersive experience may enhance intuitive understanding and allow for easier identification of certain phenomena. Further, augmented reality (AR) could be incorporated into a VR environment, where additional information could appear overlaid in front of a user over the 3D environment. The VR/AR environment could also aid in the remote operation (e.g., navigation) of rovers and other robotic spacecraft across an unfamiliar terrain (e.g., lunar or Martian surface). Traditionally, this may have been a difficult task, but it can be accomplished in VR with a simulated environment combined with additional metadata. VR provides a way to train people in scenarios that are difficult to replicate in real life. Space travel and exploration is dangerous, expensive, and requires thousands of hours of training to prepare for a mission. In particular, VR provides practical means of replicating planetary environments. Placing astronauts on the lunar or Martian surface are both examples of training environments †https://www.unrealengine. com that are re-creatable with virtual tools. One of the first VR headsets was developed in the 1970s at NASA, and newer headsets continue to serve as an important tool in astronaut training across multiple NASA centers in the Figure 1. Overview of the process used to create a VR environment of the Moon’s Taurus-Littrow Valley using a DEM constructed from LROC data. A section of the entire DEM was used to create a 1.98 × 1.95 km high-resolution mesh that was imported into a VR engine environment. Material properties and textures were applied to this mesh in Unreal Engine. 2 RPI Space Imaging Workshop. Saratoga Springs, NY. 28-30 October 2019 1 United States. Numerous publications exist that discuss the use of VR in astronaut training. Educational and outreach programs could also benefit from using exciting and immersive technology to engage both students and the general public. People of all ages and skills could benefit from learning new topics in VR environment, and experiencing life-like space environments could motivate some individuals to explore space research further. Several studies have shown how VR can impact learning outcomes, and the use of VR has been been explored in other disciplines as well. DEM to Mesh Conversion. This work makes use of a digital elevation model (DEM) of the Moon’s TaurusLittrow Valley (TLV) that was produced via stereophotogrammetry (SPG) using images from the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC). This DEM consists of terrain elevation data points arranged in a 9, 240×7, 800 grid (total of 72,072,000 data points) with a distance of 1.5 meters between each grid data point (corresponding to a terrain map for a 13.9×11.7 km section of the lunar surface). We converted this DEM into a quadrilateral mesh using a custom processing pipeline (implemented in MATLAB) to convert the DEM to a usable mesh format for the VR engine. The full TLV DEM is a mesh with 72,054,961 quad faces, which results in a several gigabytes-sized model when stored in the OBJ file format. The large polygon count makes the full size model difficult to render in real-time using a typical game engine on an everyday computer. To avoid this complication, only a small section of the full-resolution TLV mesh was imported into the VR engine environment, thus allowing real-time rendering. This created an appropriately sized model that could adequately be handled on a computer for rendering while using the headset. The section created by the authors includes about 1.7 million polygons which formed a large enough area (1.98 × 1.95 km) to allow exploration and immersion inside the VR environment. Graphics Pipeline. Virtual reality immersion relies upon photorealistic graphics that are rendered in realtime. This particular task required a scientifically accurate 3D model of the lunar terrain, a UV map of the 3D model, photorealistic lunar surface textures, a game engine that allows high quality graphics to render in realtime for VR, and a VR head mounted display. Starting with the LROC-derived 3D model of the Moon’s TLV discussed above, the UV map of the model was generated using a planar projection from the Y-axis in Autodesk Maya. UV maps are a 2D representation of a 3D model that allows a 3D model to be textured. After the model was UV mapped, it was brought into an Unreal Engine scene and set up appropriately as a VR-compatible environment. Photorealistic lunar surface textures were made for the site through Unreal Engine’s node-based Physically Based Rendering (PBR) material editor. PBR materials recognizes the way that light interacts with different materials (e.g., metal, rock). It also allows the addition of fine details that are not included in the model’s mesh, such as smaller craters, pebbles, and dust. These details were included as a multitude of layers in the normal map using uniquely patterned masks. A directional light was placed in the Unreal scene to simulate sunlight, with lowered intensity at a warmer temperature color that casts realistic shadows on the mesh surface. An Oculus Rift is used to view this scene in a virtual environment. Example renders from the VR scene in Unreal are shown in Figs. 2, 3, 4, and 5. Acknowledgments. The authors thank Rich Radke and Jason Hicken of Rensselaer Polytechnic Institute (RPI) for use of the equipment in the Rensselaer Augmented and Virtual Environment (RAVE) Lab. We also thank Daniel J. Charewicz of the Advanced Concepts Lab at NASA Langley Research Center for his assistance and guidance in Unreal Engine material building.