Multi-Resolution Stereophotoclinometry by Deformation, a New 3D Shape Reconstruction Method Applied to ROSETTA/OSIRIS Images

Abstract

We developed a new 3D shape reconstruction method which combines stereo, photoclinometry and the deformation of a triangular mesh describing the surface of the object. The method deforms the mesh - initially a sphere - until the set of synthetic images, created from the mesh (Jorda et al., SPIE 2010) match the observed one. Stereo control points can be used as a constraint in the deformation of the mesh, but it is not required at low resolutions. This new technique has been applied to images of the nucleus of comet 67P/Churyumov-Gerasimenko acquired by the OSIRIS instrument aboard the Rosetta spacecraft. The technique allowed to reconstruct the shape of the nucleus and to retrieve its rotational parameters from low-resolution images obtained with the narrow-angle camera of OSIRIS in mid-July 2014, when stereo-based techniques were still inapplicable. This model called "SHAP1" has been delivered to ESA and to the lander team in July. The technique has also been applied to higher-resolution images of the nucleus later on, using the stereo information as a constraint. A comparison of the reconstructed global and local models with those retrieved with other techniques, such as stereophotoclinometry (Gaskell et al., MPS 2008) and stereophotogrammetry (Preusker et al., PSS 2012) will be presented.