From classical ...
... to extreme adaptive optics

One of the limitations of classical Adaptive Optics (AO) originates from the fact that the correction of aberrations created by passing through a turbulent volume of atmosphere is performed by a single deformable mirror. This mirror is optically conjugated with a single turbulent layer. As a matter of fact, the correction is mainly effective in the direction of the guide star, used for aberrations sensing, but is degraded rapidly in the field of view.

The interest of the Multi Conjugate Adaptive Optics concept (MCAO), proposed more than 30 years ago, has been revealed by the work of Thierry Fusco. He has quantitatively demonstrated for the first time that a dramatic increase of the corrected field may be obtained with a very small number of deformable mirrors and guide stars. He answered to the crucial questions raised by the concept: how to distribute these mirrors and what should be measured to controlled them.

In addition, Thierry Fusco brought innovative and decisive solutions in the field of extreme AO concept, dedicated to high contrast imagery. These are concepts needed to detect exosolar planets that is faint objects near extraordinary more brilliant star.

Today, MCAO and extreme AO play a central part in the study of concepts and developments for future “Extremely Large Telescopes”. These telescopes being tens of meters wide will lead in the next decade to new scientific instruments and will ensure major advances of the knowledge in astronomy.

Very Large Telescope (4 x 8m) operational since 1998

Extremely Large Telescope European ELT :
diameter 42 m. Expected to be put into service in 2017