Observations of near-Earth objects by the Japanese infrared survey mission ASTRO-F

Abstract

The infrared astronomical satellite ASTRO-F, which has a 67 cm cooled telescope, will be launched in early 2004 and it will carry out all sky survey observation. The obtained data will be used to study various fields of astronomy, such as formation and evolution of galaxies, star formation, interstellar matter, brown dwarf, and dark matter. In addition to these, ASTRO-F also observes objects in the solar system, such as asteroids, comets, and interplanetary dust. In this paper, we investigated the possible observation for Near-Earth Objects (NEOs), especially Near-Earth Asteroids (NEAs), by ASTRO-F. The definition of NEA is the asteroids whose perihelion distance is less than 1.3 AU. At the beginning of 2002, there were about 1750 NEAs. Among these NEAs, about 250 are numbered asteroids and about 1500 are unnumbered ones. At first we studied the number of NEAs that ASTRO-F can observe during the first survey period of six months in 2004. The result is that 140 NEAs (48 numbered and 92 unnumbered asteroids) will be observed if we assume that the limiting magnitude of the observation is 20 in V band. Next we checked infrared observations in the past for these 140 NEAs and found that most of them do not have infrared data. ASTRO-F has a capability to observe at 1.8–5, 5–12, 10–26, and 50–200 μm. Using these data, we can obtain the albedo and the size of these NEAs. We think that these data will be useful not only in the scientific researches but also in the hazard analysis of asteroid collision.