This design by Ball Aerospace features four widely separated sunshields that are effective in reducing the temperature of the telescope optics and the science instrument compartment. The deployable primary mirror is mounted on three hinged slices of a 26-foot (8 meters) circular structure. By rolling the spacecraft so that the sunshade is always perpendicular to the Sun, the telescope can view half of the sky. The Ball model is designed for launch to L2 or similar orbits.