We use 414 turbulence profiles obtained by scidar over 20 nights to characterize the structure of the nighttime free atmosphere above Mauna Kea, Hawaii and to examine the isoplanatic patch enlargement that can be achieved in adaptive optics by conjugating the deformable mirror (DM) to the seeing layers. It is found that the typical night-time profile is composed of an underlying background of turbulence upon which are often superposed only one or two thin dominant layers. Low level turbulence is weak at the site. The turbulence structure is such that conjugation of a DM to turbulence rather than to the telescope entrance pupil increases the size of the isoplanatic patch by a factor of two (median); much larger gains are occasionally possible. When a single dominant layer is present, which occurs some 60 percent of the time, conjugation of the DM to that thin layer would typically reduce the seeing spread angle by a factor of two over a field of view of many arcmins. These results should be useful in the design and evaluation of AO systems for the site.

Date Published: 25 August 1995
PDF: 10 pages
Proc. SPIE 2534, Adaptive Optical Systems and Applications, (25 August 1995); doi: 10.1117/12.217743

Published in SPIE Proceedings Vol. 2534:
Adaptive Optical Systems and Applications
Robert K. Tyson; Robert Q. Fugate, Editor(s)