The SPACE testbed is designed to emulate a Cassegrain telescope of 2.4-meter focal length with performance comparable to an actual space-borne system. The system's top-level requirements figure maintenance of the primary mirror to within 1 micron RMS distortion with respect to a nominal shape of the primary mirror, pointing accuracy of 2 arc seconds, a high level of disturbance rejection (100:1), and attenuation of vibration due to gravity, thermal and seismic effects, and control structure interaction. The primary mirror is composed of a ring of six actively controlled hexagonal panels arranged around a central panel. The central panel is fixed and serves as a point of reference to the moving panels. The testbed is a control-oriented experimental system and due to the difficulty and added expense of actual optical quality segments made from glass, the panels are made of aluminum honeycomb plates. The required paraboloid surface is thus maintained by positioning the flat panels as tangents to the surface.