The SMT woofer-tweeter system design has four key assumptions. First, the wavefront disturbances are low frequency allowing the two mirrors to operate at the same bandwidth. Second, the wavefront sensing system measures the combined wavefront error of the primary mirror and the additional deformable mirror. Third, the individual segments are phased relative to each other and piston, tip, or tilt error is removed using the individual segment coarse and fine actuators. Fourth, the SMT AHM segment and deformable mirror responses are designed to be linear, and the actuator responses obey the principle of linear superposition.