Spacecraft Hayabusa (Falcon) sample return mission to asteroid Itokawa

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The Falcon Has Landed

“The falcon cannot hear the falconer;
Things fall apart.”
-Yeats   [1]

Hayabusa (Falcon)

Hayabusa is a small, relatively inexpensive, spacecraft sent to observe a Near-Earth Object (NEO) and demonstrate the ability to successfully perform an automated sample return mission.

The craft was deployed and controlled by JAXA (Japan Aerospace Exploration Agency) with contributions from other space faring agencies worldwide.

The selected NEO target was Asteroid 25143 Itokawa (1998 SF36). Itokawa was the target chosen because its orbit intersects orbits of both Earth and Mars. With this choice, the mission design team would have a good baseline for data for different types and destinations of future missions. [2]

Mission control problems run amok

Like so many prior deep space missions, both manned and unmanned, the Hayabusa excursion had plenty of failures paving the way for heroic ground control engineers to attempt to salvage the project by ingenuity (and luck).

Among the potentially devastating list of problems with the craft were the lost communication with ISAS (Institute of Space and Astronautical Sciences JAXA), lost hydrazine propellant, dead batteries, MINERVA the lander/rover robot was lost to space due to an unwanted spin caused by the handicapped attitude control (part of the handicap was lost propellant, part failed engines, failed guidance systems, failed…).

The intelligent design of this spacecraft however, allowed for the probe to function autonomously until communications could be reestablished and mission adjustments could be made. Once ground control was able to reestablish a working com-link, an inventory revealed that functional instruments included imaging camera (to send back pictures of the target and to assist in landing site selection), the ever crucial laser altimeter (to determine how far from the surface landing sequences should properly begin), Near-Infrared Spectrometer and the X-Ray fluorescence spectrometer used to determine the chemical composition of the target asteroid and just maybe, the sample return probes (the probes were deployed, but whether valid samples were taken cannot be determined {possibly due to yet another faulty…}) [2]

The Rubble-Pile

Itokawa is referred to as a rubble pile asteroid because its physical properties are akin to those of a loosely piled heap of rubble or rock. Itokawa has a very low density estimated at 1.9 +/- 0.13 g cm^-3 when compared to other asteroids previously visited such as Eros with the NEAR spacecraft. The asteroid’s mass averaged to be 3.51E10 +/- 0.105E10 kg, again for its size, fairly light, which supports the low density readings. Also, an unexpected high porosity (>40%) further supports the notion of a loosely packed pile of rock. Expected porosity for such a quickly spinning galactic body (~12.1 hour/rotation) was ~20%.[3]

Spectral Results

Near-Infrared Spectral imaging taken by Hayabusa revealed a varied and unevenly distributed physical makeup. Variations in surface reflectance indicated that the typical pock-marked surface was present, but absent were the deep craters typically seen on moon-like or asteroid-like bodies to date.

The asteroid’s rich mineral composition seemed to suggest that Silicon played a large part in the structure of the space body along with other Earthly elements such a Aluminum. Similar chemical composition to other asteroids however was rather enigmatic in the face of a larger diversity in physical size of specimens compared to other asteroids. Rather than be all large boulders and chunks of boulders, it would appear that a large portion of Itokawa is actually smaller, gravel sized pieces that filter down and settle at the bottom of craters and hillsides on the asteroid to help smooth and “soften” the image data displayed to its admirers, telescope assisted humans on Earth and robotic star voyagers like Hayabusa.[4]


{After having assumed that Hayabusa was already en route back to Earth earlier, and having been quizzed about that during class I checked… here’s what I found… - Mitch}

Apparently more system failures have plagued the beleaguered craft and workarounds have been found and although on only 50% of the propulsion drives, Hayabusa will actually begin its return trip back to Earth in February 2007 and is expected to drop a re-entry capsule containing the Itokawa samples back to the waiting arms of scientists in 2010.


[1] J. Baker, “The Falcon Has Landed”. Science, Vol 312., p 1327, 2 June 2006

[2] E. Asphaug, “Adventures in Near-Earth Object Exploration”. Science, Vol 312., pp 1328-1329, 2 June 2006

[3] A. Fjuiwara et al. “The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa” Science, Vol 312., pp 1330-133, 2 June 2006

[4] M. Abe et al., “Near-Infrared Spectral Results of Asteroid Itokawa from the Hayabusa Spacecraft” Science, Vol 312., pp 1334-1338, 2 June 2006

[5] T. Okada et al., “X-ray Fluorescence Spectrometry of Asteroid Itokawa by Hayabusa” Science, Vol 312., pp 1338-1341, 2 June 2006

[6] J. Saito et al., “Detailed Images of Asteroid 25143 Itokawa from Hayabusa” Science, Vol 312., pp 1341-1344, 2 June 2006

[7] S. Abe et al., “Mass and Local Topography Measurements of Itokawa by Hayabusa” Science, Vol 312., pp 1344-1347, 2 June 2006

[8] H. Demura et al., “Pole and Global Shape of 25143 Itokawa” Science, Vol 312., pp 1347-1349, 2 June 2006

[9] H. Hano et al., “Touchdown of the Hayabusa Spacecraft at the Muses Sea on Itokawa” Science, Vol 312., pp 1350-1353, 2 June 2006

[10] “Orbit Simulation - Asteroid 25143 Itokawa (1998 SF36)” [29 January 2007].

[11] “Hayabusa” 22 January 2007 [29 January 2007].

[12] “NSSDC Master Catalog Display: Spacecraft - Hayabusa (Muses-C)”  [29 January 2007].