The northern hemisphere of asteroid (21) Lutetia—topography and orthoimages from Rosetta OSIRIS NAC image data

During the flyby at asteroid (21) Lutetia by the Rosetta spacecraft in July 2010, the OSIRIS imaging system onboard acquired several hundred images of Lutetiaʹs surface. Images of the OSIRIS NAC (Narrow Angle Camera) comprise up to 60 m/pixel ground resolution. We analyzed 84 multi-spectral NAC images with stereo-photogrammetric methods. A 3D point control network within a photogrammetric block adjustment was used to derive improved orientation data (pointing and position) for the Rosetta spacecraft as well as corrections of the pre-flight estimates of Lutetiaʹs position in space. For the generation of a digital terrain model (DTM), we selected a subset of 10 OSIRIS NAC images within a multi-image matching process. We combined the matching results with the adjusted orientation data and derived more than 12 million of surface points with a 3D point accuracy of ∼40 m (2/3 pixel) and a vertical component of that of ∼15 m (1/4 pixel). The 3D surface points were converted to a final 60 m raster DTM, which covers about 78% of the entire northern hemisphere. All 84 NAC images were then ortho-rectified on the basis of the improved orientation and the DTM. Thus, orthoimage products with sub-pixel registration accuracy are available for multi-spectral mapping of the surface of Lutetia. Finally, the DTM was textured with an orthoimage mosaic to form a VRML dataset for full-resolution interactive 3D investigations.