CCD reflectance spectra of selected asteroids: I. Presentation and data analysis considerations

Abstract

Narrowband reflectance spectra of 35 asteroids have been obtained with a CCD spectrograph from 1984 to 1987 as part of a search for weak features in the reflectance spectra of asteroids that would expand our knowledge of their surface mineralogical composition. Spectra obtained of primitive asteroids were examined for evidence of aqueous alteration products. The spectrum of 1 Ceres shows weak absorption features at 0.60 and 0.67 μm not yet explained by laboratory reflectance spectra. Spectra of some main-belt and outer-belt C- and P-class asteroids show weak absorption features that have analogues among spectra of CM carbonaceous chondrites and terrestial phyllosilicates. Weak absorption features are seen in the spectra of some asteroids located in the Hilda and Cybele groups beyond the outer edge of the main asteroid belt that do not have analogues among laboratory spectra. The Trojan D-class asteroids observed show no sign of absorption features, suggesting that aqueous alteration did not operate at that heliocentric distance. Features present in the spectra of ordinary chondrites were sought in spectra of asteroids located in possible source regions for the ordinary chondrites. Spectra of asteroids located near the 3:1 Kirkwood Gap both in and outside of the proposed chaotic zone show no resemblance to laboratory spectra of ordinary chondrites.