LUTETIA 21 Asteroid reconstruction by structure from motion and photometric techniques

Rubino C. Master Thesis

by: Rubino Cosimo

Thesis Title:

LUTETIA 21 ASTEROID RECONSTRUCTION BY STRUCTURE FROM MOTION AND PHOTOMETRIC TECHNIQUES

The goal of my experimental work of thesis is the reconstruction of the northern hemisphere surface of the asteroid 21 Lutetia, which is one of the two objectives of the International Rosetta mission, whose images were acquired during the spacecraft fly-by on July 10, 2010.

By analizing image sequence captured by the optical imaging system mounted on the probe, it has been possible to generate the sparse surface by using some geometric properties.

Detected features without filtering	SfM reconstruction

With this unregistered and unscaled structure of features, it is possible to recover the position of the reconstructed part in a Lutetia-fixed based frame by using the geometric data provided by SPICE. SPICE is a ancillary information system developed by NASA, wich can give distances and orientation between bodies associated with many space mission.

KOALA and SfM merging	KOALA reconstruction with SfM 3D features

The main purpose of the master thesis work was to generate a dense reconstruction of the asteroid, and this target was reached by using the Shape from Shading technique.

SFS reconstruction

This metod, based on the main ipothesis of a Lambertian surface ( with an isotropic surface luminance ) may generate with a single image and the light direction a dense 3D reconstruction; the lackness of this method is a bad low spatial frequency recognition.

The final solution was to combine, with a appropriate cutoff frequency, the low frequency of the Structure from Motion reconstruction with the Shape from Shading relieves.

Dense reconstruction by high and low spacial frequence union	Final surface shape

This method generated a dense surface reconstruction with a good shape refinement.