From the BBC:
Japanese scientists are celebrating the successful deployment of their solar sail, Ikaros.
The 200-sq-m (2,100-sq-ft) membrane is attached to a small disc-shaped spacecraft that was put in orbit last month by an H-IIA rocket.
Ikaros will demonstrate the principle of using sunlight as a simple and efficient means of propulsion.
The technique has long been touted as a way of moving spacecraft around the Solar System using no chemical fuels.