ISO observations of low and moderate albedo asteroids

Abstract

The ISO observations presented here are devoted to low and moderate albedo asteroids, which are supposed to be among the more primitive objects of the solar system. Spectroscopic and multi-filter photometric data of 77 Frigga, 114 Kassandra, 308 Polyxo, 511 Davida, and 914 Palisana have been obtained by the ISO instrument ISOPHOT. The subsystem PHT–P carried out photometric observations at 10, 12, 25, and 60 μ m, while low resolution spectra have been acquired by the subsystem PHT–S between 5.8 and 11.6 μ m. The Standard Thermal Model and a black-body fit have been applied to the obtained data in order to model the thermal continuum and to derive sub-solar and black-body temperatures. To interpret the obtained results and to investigate the surface composition of the observed asteroids, we compare the ISO spectra with the whole sample of mineral and meteorite laboratory spectra available in the literature. New laboratory experiments performed at the Capodimonte Observatory have been carried out to increase the available sample. A tentative spectral similarity with meteorites is presented.