Photogrammetric 3D reconstruction of Apollo 17 Station 6: From boulders to lunar rock samples integrated into virtual reality

Abstract

Apollo 17 astronauts spent three days exploring the Taurus Littrow Valley on the Moon in 1972. During their third Extravehicular Activity, they spent more than 1 h at Station 6, a geologic waypoint consisting of three big and two small fragments of a boulder that rolled down the North massif. We have used all the available scanned digital Apollo photos taken by the astronauts at this Station 6 to compute a comprehensive 3D model of the explored area. We used Structure From Motion photogrammetry to automatically derive the position of each of the 154 available images using their overlap. All images were aligned in a single photogrammetric project, which allows on one hand to automatically visualize the astronaut positions during their investigations, and on the other hand to reconstruct in 3D the three main pieces of boulders, therefore constraining their respective size and orientation. In addition to the boulders, we show that the 3D reconstruction by photogrammetry can also be applied to the rock samples taken from the boulders themselves. These samples were systematically photographed from multiple angles at the LPI during the 70s when brought back to Earth. For the reconstruction, we used scanned archived images representing 16 stereoscopic pairs, to compute 3D models of samples 76015, 76215, 76315 and 76275. These models might play a role in preservation as some of the samples, latter sawed for analysis, do not exist anymore in their pristine form. 3D models of the boulders and rock samples can then be manipulated and visualized on a web-based platform. 3D models have also been integrated into a virtual reality scene in order to provide the possibility to investigate their properties at full scale in an immersive and collaborative way. The knowledge of the samples position and orientation directly in their context might for example provide additional constrains to better understand processes such as the space weathering alteration due to micrometeorite impacts and solar wind particle. 3D photogrammetric reconstructions using images taken by rovers and/or astronauts might be one of the basic techniques to consider in forthcoming lunar missions in order to maximize their scientific, educational and outreach return.