NOVELTY - Primary stage has inner mirror surface for accepting solar radiation from entrance and directs radiation to exit. Secondary stage abutted to exit of primary stage, has biaxial gradient refractive index element comprised by gradient refractive index materials with high and low index surfaces. The index element is oriented such that high index plane is perpendicular to entrance and exit of secondary stage.    USE - For concentrating solar radiation onto solar cells used in space related vehicles such as low earth orbit (LEO) telecommunication satellites, mid earth orbit (MEO) military and research satellites, and also in large variety of geosynchronous earth orbit (GEO) applications. Also for missions that require radiation hardened systems or high concentration of solar radiation for deep space missions.    ADVANTAGE - Includes Bezier surfaces in tandem with biaxial lens, thereby increases off angle performance of concentrator by bending power of gradient index of refraction in biaxial lens and total internal reflection by walls of biaxial element. Reduces chromatic aberration even at high concentrations using simple technique. Improves storage power density with nesting capability and excels in thermal management with advanced composite system. Facilitates to use conventional flat PV panel mounting and deployment technology.    DETAILED DESCRIPTION - The primary stage has concentrator cusp (34) whose bottom supports the secondary stage. The two of sides of the cusp are longer than other two sides. The longer sides comprising Bezier surfaces are parallel to the high index plane of the secondary stage. The cusp contains flexible electronic circuitry strips on its outer surfaces for permitting nesting of cusps. The mirrored surfaces of the primary stage are protected with dielectric coating or coating selected from group containing silica, titania. Solar cells are arranged in exit surface of biaxial gradient refractive index element.    DESCRIPTION OF DRAWING(S) - The figure depicts enlarged perspective view of lower portion of concentrator showing biaxial lens, solar cells and substrate which supports the solar cell.    Concentrator cusp (34)