KORONIS FAMILY - REFLECTANCE SPECTRA OF 243 IDA, 1442 CORVINA AND 2226 CUNITZA

Low-resolution spectra of the asteroids 243 Ida (target of the Galileo spacecraft on 28 August 1993), 1442 Corvina and 2226 Cunitza (other members of the Koronis family) were obtained. In the frame of a ground-based international campaign to observe Ida before the Galileo encounter (Binzel et al., Icarus, in press, 1993), we observed it spectroscopically in the visible at ESO-La Silla (Chile), obtaining four spectra covering the total rotational period (4.63 h). In one of these spectra, we observed a considerable variation in the depth of the absorption feature near 0.9 mum, implying a different content of pyroxene and olivine on the surface of Ida. The spectra obtained for the other two objects are consistent with those of S-type asteroids and similar to that of Ida.