Ground Layer Adaptive Optics

Adaptive optics (AO), technologies for sharpening images in astronomical observations, has seen a maturing in recent years, and AO instruments are increasingly becoming an integral part of modern optical observatories. A number of novel technology concepts are currently being investigated for the next generation of AO instruments. Examples are wide-field-of-view multi-conjugate adaptive optics (MCAO), or extremely-high-order AO (XAO), which are both expected to be required by future extremely large telescopes (ELTs), or for very-high-contrast imaging (“planet-finder” instruments) on the current 8-m class telescopes. While MCAO and XAO address some of the shortcomings of conventional AO and try to extend the parameter space, they both require complex and expensive solutions, and still do not cover the full parameter space of the AO domain. There is a gap at the wide-field low-order end, that the concept of ground-layer adaptive optics (GLAO) is poised to address by a variety of different techniques that have been proposed.

GLAO is a novel but as yet unproven concept that has attracted a fair amount of attention within the AO community recently. Its aim is to provide future AO instruments on astronomical telescopes with a new mode of turbulence compensation. By correcting only low-altitude turbulence, GLAO offers low-order compensation over a much larger field of view than conventional AO, with a spatially invariant point spread function being one of the desirable goals of GLAO turbulence compensation. The proposed methods for accomplishing this include aspects of, e.g., tomographic wavefront sensing and reconstruction algorithms, low-altitude laser guide stars that are insensitive to high-altitude turbulence, and exploiting the particular site characteristics where possible.

The aim of this workshop is on the one hand to provide a stimulating setting for researchers in the field, both for exchanging information and for working together on common problems to generate new solutions. We also hope to evolve a better appreciation of the various GLAO methods proposed, as well as an understanding of its role and importance in the parameter space of astronomical AO. Apart from technical issues concerning modeling, optimization and implementation of GLAO, it is a goal of the workshop to address the underlying issues, such as the value of GLAO to the scientific community, what are the limitations of the technique, and how do we go about verifying the concept experimentally.