While single conjugated adaptive optics delivers high Strehl ratios on axis, this method suffers generally from angular anisoplanatism. Only a small field over the isoplanatic patch is well corrected with the performance degrading towards the edges quickly. Ground layer adaptive optics, utilizing multiple laser guide stars is generally capable of correcting a larger field of view. This technique has been demonstrated already with the use of natural stars and recently with Rayleigh guide stars at the MMT.
Ground layer adaptive optics offers some general benefits which are not associated with reaching the diffraction limit. The advantages here lie in the enhanced resolution, the increased point source sensitivity and slit coupling efficiency as well as the robustness against crowding. Offering those advantages over a large field of view makes up the uniqueness to enhance the scientific capabilities of the LBT.
Model calculations show the achievement that can be reached with laser guided ground layer adaptive optics.
(Left) Gain in FWHM with ARGOS GLAO correction. (Right) FWHM of the corrected PSF (solid lines) and of the uncorrected one (dashed). Colours identify the 4 different atmospheric profiles.
(Left) Gain in ensquared Energy with ARGOS GLAO correction. (Right) Ensquared Energy in a 0.25’’ square pixel of the corrected PSF (solid lines) and of the uncorrected one (dashed). Colors identify the 4 different atmospheric profiles defined in [AD1]