Presently, the number of known asteroids is more than 710,000. Knowledge of size and albedo is essential in many aspects of asteroid research, such as the chemical composition and mineralogy, the size-frequency distribution of dynamical families, and the relationship between small bodies in the outer solar system or comets. Recently, based on the infrared all-sky survey data obtained by IRAS, AKARI, and WISE, the large asteroid catalogs containing size and albedo data have been constructed. In this paper, we discuss the compositional distribution in the main belt regions based on the compiled data on size, albedo, and separately obtained taxonomic type information.

ABSTRACT
1. INTRODUCTION
2. DISTRIBUTION OF THE MAIN BELT ASTEROIDS
    2.1. Size-albedo distribution
    2.2. Heliocentric distribution of albedo
3. CONCLUDING REMARKS
REFERENCES

• Fumihiko Usui(Center for Planetary Science, Graduate School of Science, Kobe University)
• Sunao Hasegawa(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency)
• Masateru Ishiguro(Department of Physics and Astronomy, Seoul National University)
• Thomas G. Muller(Max-Planck-Institut fur Extraterrestrische Physik)
• Takafumi Ootsubo(Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, The University of Tokyo)