Geoscience Reference
In-Depth Information
The XRF is a well-established technology for both qualitative and quan-
titative elemental analysis in the laboratory. The difference of the space
XRF is that the excitation source is not a generator but the Sun. As was
proven during the Apollo 15 and 16 missions,
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the major elemental compo-
sition of an atmosphere-free planetary surface can be determined through
this method. The Near-Earth Asteroid Rendezvous mission to Asteroid 433
Eros and the SMART-1 lunar orbiter mission also have the XRS.
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,
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The
instrument has been used for many previous missions, and will be also
used for the coming lunar orbiter missions such as the Japanese SELENE,
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the Indian Chandrayaan-1, and the Chinese Chang'E as well as the Mer-
cury missions of the NASA's MESSENGER
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and the ESA-Japan's Bepi
Colombo.
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In this paper, we present the objectives and specifications of the XRS
instrument onboard Hayabusa. The method of onboard analysis and some
results of pre-flight and in-flight experiments are also described.
2. Overviews of the Hayabusa Mission
Hayabusa
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has been launched on May 9, 2003, by the fifth M-V launch
vehicle. After one-year cruise by using the ion engine system, the spacecraft
has swung by the Earth for acceleration with terrestrial gravity assist. In
September of 2005, it will arrive at 25143 Itokawa, which is a near-Earth
asteroid of elongated shape (about 540 m
210 m) and classified as
S(IV) type. Hayabusa will characterize the asteroid through remote sensing,
followed by sample collections of the uppermost surface material. These
samples will be recovered by direct re-entry from the interplanetary orbit
in June, 2007.
The mission aims at the technology demonstration of sample return from
a near-Earth object. But it also has high scientific significance, since several
remote sensing instruments including the XRS and the robotic lander for
characterization of the asteroid are mounted on it, as well as instrumenta-
tion for the very first rocky sample return from a solar system body other
than the Moon.
×
290 m
×
3. Science and Instrument of the XRS
3.1.
Scientific objectives
The XRS is to determine major elemental composition of Itokawa such as
Mg, Al, Si, and S. Heavier elements such as Ca, Ti, and Fe will be also
