1.   The current flexible arrays of silicon cells, which roll up and down like window shades, will be replaced by rigid panels of more efficient gallium arsenide cells.

2.   The flat panel, about the size of a queen-sized mattress, is covered with silicon cells that convert sunlight into electricity.

3.   When light falls on the surface of the silicon cells, it is converted into an electric charge in proportion to the brightness of the light.

4.   The old wings being returned to Earth are made of silicon cells.