Auxiliary telescopes redirect light to enhance the main telescope's resolution, which means that mirror stability is critical. This is particularly true since the telescopes continue to rotate slowly while measurements are being carried out, and the weight of certain elements causes the structure to flex, resulting in inaccuracies. CSEM's engineers have developed precision mechanisms that are mechatronic masterpieces: extremely stiff hexapods that guide and control each telescope's secondary mirror with a precision and stability of around one micrometer. These devices compensate for the inaccuracies generated during the rotation of the telescopes. CSEM delivered five, six degrees of freedom hexapods, three of which have now been installed on the secondary mirrors of the VLT's auxiliary telescopes.
To learn more:
Compensating for atmospheric disturbances with NAOS
2001–present | When viewed from Earth, stars appear to twinkle, yet the light they generate is constant. This misleading effect is due to turbulence in the Earth's atmosphere (variations in temperature, pressure, etc.), which disrupts incoming light from stars.
Yepun, one of the four main VLT telescopes at Cerro Paranal, uses optical techniques to actively compensate for these disturbances, via the NAOS (Nasmyth Adaptive Optics System) facility. When the light reaches the telescope, perturbations caused by atmospheric turbulence are analyzed, a correction signal is generated and then subsequently sent to a deformable mirror. This mirror is fitted with several hundred actuators, which adapt the wavefront in real time, allowing the light emitted by a star to be reconstructed as it was before it entered the atmosphere. This feature enables the eight-meter Yepun telescope to observe objects with a resolution close to the theoretical limit.