Octant solar arrays Four octants of solar array serve five functions: (1) generate power at all azimuths and elevations of solar incidence - without pointed arrays (2) radiate heat from white surface interspersed between cells (3) conduct heat from plane-to-plane to cool hot-spots (4) enclose robot to preclude dust from interior (5) achieve structural strength and rigidity of folded planes

From AstroboticBlogPhotos