The microwave discharge ion engines onboard HAYABUSA asteroid explorer have marked space operation of twenty thousands hour and unit as the accumulated operational time on December 9th.

HAYABUSA spacecraft, which was launched on May 2003, succeeded the Earth swing-by on May this year and continues to transfer into the asteroid using the acceleration by the ion engines.

They generated 1,300m/s delta-V consuming 20kg propellant up to now. After September the space maneuver using three ion engines was throttled down in order to adapt power reduction of the solar array panels due to enlargement of solar distance.

Furthermore one of three engines was turned off in the middle of October. The spacecraft stays in deep space 1.3 astronautical unit apart from Earth. The communication time lag exceeds twenty minutes, which is the time duration between sending commands and confirming answers on Earth. The telemetry bit rate is also gradually falling, so that the operation team feels helpless.

HAYABUSA spacecraft, which is executing the maneuver operation diligently and automatically in the lonely deep space, is sturdy and dependable rather than us.