Hayabusa is still 100 million kilometers from the Earth, less than an astronomical unit away but still with months to travel. But according to an update posted to their website this morning by project manager Junichiro Kawaguchi, Hayabusa is on the home stretch. Even if Hayabusa's ion engines were to quit now, it would pass within 2 million kilometers of Earth, a distance five times the Moon's orbital radius and only 1.4 times the breadth of Earth's gravitational influence (according to them).
JAXA / ISAS / Hitoshi Kuninaka
With its recently reconfigured ion engines, Hayabusa is still patiently thrusting, and the goal now is to give the orbit the slight shift it needs to be brought under the sway of Earth's gravity. "Getting into Earth gravity field now becomes real, and will be confirmed in the middle of January," the update says. Hayabusa approaches Earth at the rate of 150 to 200 thousand kilometers per week (or about a quarter to a third of a kilometer per second), a rate that seems quite slow but it's because Hayabusa and Earth are both traveling around the Sun at very similar speeds of 30 kilometers per second.
The update closes "The Hayabusa project team will update whenever any new information becomes available. We will soon be ready to say Welcome Back Home, Hayabusa." Dare we hope that Hayabusa will return its sample capsule? The target return date is in June of next year.
ISAS / JAXA
Hayabusa's trajectory, December 2008
In December 2008, Hayabusa was slowly approaching Earth.