In June 2006, an image of the asteroid Itokawa taken by HAYABUSA graced the cover of the American academic journal Science, which is rivaled in prestige only by its British counterpart Nature. That image heralded a special issue featuring six theses on what HAYABUSA found.
Asteroids are generally imagined to be solid chunks of rock. Around 1990, however, a new hypothesis emerged: they might instead be rubble piles consisting of a loosely bound, highly porous agglomeration of rocks of different sizes.
That hypothesis was first corroborated by HAYABUSA. And a panoply of NEC technology played a key role in bearing it out.
Images taken by the cameras aboard HAYABUSA, and readings taken with its LIDAR laser rangefinder, revealed Itokawa’s shape in three dimensions, enabling its volume to be calculated. Further, its gravity was measured during the spacecraft’s descent and orbit and its density was calculated, making it possible to work out its mass (weight) as well. This analysis of the observed data showed that Itokawa was a low-density object, with an average density of 1.9g per cubic centimeter, confirming that Itokawa was indeed a rubble-pile asteroid — the first to be observed by human eyes.