(25143) Itokawa

Template: Infobox Asteroid / Maintenance / Error 2

( 25143 ) Itokawa (1998 SF36 ) is discovered on 26 September 1998, the Earth's orbit crossing near-Earth asteroid. It was named after celestial bodies Hideo Itokawa, a Japanese rocket scientist.

Orbit

Itokawa moves between 0.953 AU ( perihelion ) and 1.695 AU ( aphelion ) in about 556 days on an eccentric orbit around the sun. During the perihelion, the asteroid moves within the Earth's orbit. The orbital eccentricity is 0.280, the orbit is inclined 1.6 ° to the ecliptic.

Ground-based observations

Radar observations of the observatories Goldstone and Arecibo have shown that it is Itokawa an elongated structure is 320 × 288 meters with a size of only 594 ×. The surface appears to be predominantly of siliceous material, similar to ordinary chondrites. In around 12 hours, the asteroid rotates around its own axis.

In the measurement of rotational speed for calculating the Itokawas YORP effect, a deviation of the actual from the expected change in the speed was noted. Only when in the calculation assumed that the asteroid consists of two parts with differing densities, voted the measurement results agree with the calculated change in rotation speed. Itokawa must therefore from a part having a density of 2850 kilograms per cubic meter and a second consisting of a density of 1750 kilograms per cubic meter. This observation is unique in asteroids. It is believed that Itokawa was the collision of two asteroids.

Spacecraft Hayabusa

Itokawa was selected as a target for the Japanese Hayabusa mission. The recordings of the probe has reached Itokawa in September 2005, show the asteroid's surface with a resolution of less than one meter. Striking is the almost complete absence of impact craters that dominate the surfaces of other asteroids such as at ( 243) Ida or ( 433 ) Eros, which have been explored by spacecraft. Some areas on Itokawa is covered by regolith and rocks of various sizes, elsewhere apparently is bare rock free. The size of Itokawa was set 209 meters by 535 × 294 × on Hayabusa and the mean density of 1.95 ± 0.14 g / cm ³ to be determined. This corresponds to the density of the asteroid roughly the sand and is well below the value of ordinary chondrites (about 3.2 g / cm ³). These observations suggest that it is the asteroid to a held together only by the force of gravity " pile of rubble " (English rubble pile ) is having a porosity of about 40%. However, this hypothesis needs to 2006 in light of the discovery of 2014 that the asteroid consists of two parts significantly different density, to be re- considered.

Hayabusa took in November 2005 at two different points on the surface of the asteroid samples. After the first attempt on 19 November had failed, the mechanism of sampling at the second attempt worked on 26 November properly. The launch window could not be used in December 2005 due to loss of communication with the ground station; However, Hayabusa was launched in 2007 using its ion engines back to Earth. The return capsule of the space probe occurred after one overshadowed by various technical problems return flight on June 13, 2010 at 15:51 CEST on Australia in the Earth's atmosphere and landed on schedule at the Australian Woomera in the WPA.

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