Design and Performance Analysis of Adaptive Optical Telescopes Using Laser Guide Stars.

摘要

Atmospheric turbulence severely limits the resolution of ground-based astronomical telescopes. In good seeing conditions at the best observatory sites, resolution at visible wavelengths is typically limited to approx. 1 sec of arc. During the past 15 years adaptive optical systems using electrically deformable mirrors have been developed to compensate for turbulence effects. Unfortunately, these systems require bright reference sources adjacent to the object of interest and can be used to observe only the brightest stars. Artificial guide stars suitable for controlling an adaptive imaging system can be created in the upper atmosphere by using a laser to excite either Rayleigh backscattering in the stratosphere or resonance backscattering in the mesospheric sodium layer. The design requirements of a laser-guided adaptive telescope , as well as the expected imaging performance, are discussed in this thesis. Analytical expressions giving the performance of a class of adaptive optics systems using slope sensors are derived. We show that a two-meter, ground-based, laser-guided telescope can achieve imaging performance levels at visible wavelengths nearly matching those of the Hubble Space Telescope (HST). Design examples, including lidar systems for atmospheric research and laser-guided telescopes, are studied in detail. (rh)