Observation Plan of Asteroid Itokawa Using the XRS onboard Hayabusa

Abstract

The Hayabusa will rendezvous 25143 Itokawa, an S (IV)-class near-earth asteroid, in September to October, 2005. The XRS is among the remote sensing instruments aboard. We present here the main objectives of the XRS observation. The XRS will determine major elemental composition of surface of the asteroid. Elemental variation will be surveyed by asteroid rotation in longitudinal direction, maybe with spatial resolution of 60 degrees. The XRS always detect such major elements as Mg, Al, Si, and S, but it also can do for higher atomic number elements such as Ca and Fe, especially during the occurrence of solar flare. Furthermore, microscopic roughness of the surface is informed by observation at various solar phase angles due to particle size effect in X-ray fluorescence. Since thermal design of the XRS has been well calibrated, thermal radiation intensity off the asteroid surface will be estimated by monitoring the temperature profile during descent of the spacecraft for asteroid touchdown.