Optical and infrared studies of asteroids.

This thesis presents optical and infrared data of asteroids. The basis of the classification of asteroids by numerical taxonomy is data which are contained in the TRIAD file (Zellner, 1979). The resulting dendrograms are compared with existing classes of asteroids. Simultaneous visible and near-infrared lightcurves of several asteroids are plotted as colour curves which, in some cases, show variations indicative of an inhomogeneous surface composition. The colour curves of 4 Vesta are explained in terms of eucrite and diogenite mineralogies. Some of these lightcurves, together with published data from previous oppositions, are used to calculate the overall shape of the asteroid and the orientation of the spin axis. These are calculated using a lightcurve amplitude-longitude relation. Reflectance spectra in the 3 - 4 ?m region are presented, Two of which show evidence of water of hydration. These spectra highlight the importance of accurate thermal modelling. Data from IRAS is compared with the expected flux from the standard asteroid thermal model and the discrepancies examined in terms of emission from the unilluminated hemisphere.