[en] The spectral reflectivity of asteroid surfaces over the wavelength range of 0.3 to 1.1 μm can be used to classify these objects onto several broad groups with similar spectral characteristics. The three most recently developed taxonomies group the asteroids into 9, 11 or 14 different classes, depending on the technique used to perform the analysis. The distribution of the taxonomic classes shows that darker and redder objects become more dominant at larger heliocentric distances, while the rare asteroid types are found more frequently among the small objects of the planet-crossing population

[en] The principles of asteroid light-curve inversion are discussed together with basic principles involved in approaches for deriving asteroid pole and shape parameters from photometry data. The merits of various pole determination techniques are described and compared. Results obtained so far on the pole orientations and shapes of asteroids are presented. 78 refs

[en] Asteroids are believed to be remnant planetesimals from the crucial period of planetary formation. They are located in the transition region separating the terrestrial planets from the Jovian ones, where the planetary formation process interrupted at the intermediate stage owing to an unknown mechanism, probably associated to the gravitational influence of the massive proto-Jupiter. Asteroid eccentricities and inclinations were pumped up, thereby increasing collision velocities and transforming the accretion among planetesimal into collisional destruction and erosion. Impacts have altered sizes, physical structures, rotation rates and spin axis directions of most of the asteroids over the course of solar system history; however, the magnitude of these changes is not yet well understood. Asteroids constituted of essentially unalterated primitive material preserve important information about the chemical composition and the environmental condition of the protoplanetary nebula and the processes that produced the planetary bodies. The knowledge of these small bodies has considerably improved over the last twenty years, by means of Earth-based observations. In this paper we discuss the current knowledge on the nature of the asteroid population and the related constraints on the solar system formation

[en] The principles of asteroid lightcurve inversion and the information available from photometry are reviewed. General tools as well as specific techniques for shape and pole determinations are summarized and their advantages and shortcomings are discussed. The authors present the results obtained so far in this very active field and discuss their significance in the general context of asteroid research and planetary formation