Power spectral densities of the simulated aberrations. The upstream and downstream aberrations are randomly generated according to a f^-2 spectrum and with an rms value of 30 nm. The downstream aberrations are not corrected by the adaptive optics. The upstream aberrations are corrected by the adaptive optics up to 20 cycles/pupil. The residuals are due to the non-common path aberrations. Below 4 cycles/pupil, these non-common path aberrations are corrected but there are some residuals from rotative optics.