Phase II of the Small Main-Belt Asteroid Spectroscopic Survey: The Observations

We present visible-wavelength (0.435–0.925 μm) spectroscopic measurements for 1341 main-belt asteroids observed during the second phase of the Small Main-belt Asteroid Spectroscopic Survey (SMASSII). The purpose of this survey is to provide a new basis for studying the compositional structure of the asteroid belt. Through the large sample size and the relatively high spectral resolution (R∼100) of the SMASSII data, we find that values of the spectral parameters describing these data form more of a continuum than previously realized. Objects with intermediate spectral characteristics are bridging gaps that once separated distinct spectral classes. In some cases, newly revealed small-scale spectral features may be indicative of previously unrecognized mineral constituents. Here we present the data and principal component analyses that describe the SMASSII spectra. A companion paper utilizes these principal component scores, along with other measures of the spectral features, to develop a new taxonomy that takes advantage of the information contained within charge-coupled device spectra.