An instrument named the grating scale monitor for measuring the outer scale ℒ<sub>0</sub> from the angle-of-arrival (AA) fluctuations of a perturbed wave front was developed a few years ago at Nice University. The AA is detected with a 5-ms time resolution by modulation of the stellar image in a small telescope with a grating. One uses the normalized covariance of AA fluctuations to estimate ℒ<sub>0</sub>. A new version of this instrument, the generalized seeing monitor (GSM) is described. It consists of four identical modules for measuring the AA at four locations on the wave front. A spatiotemporal analysis of these data leads to the determination of seeing ε<sub>0</sub>, outer scale ℒ<sub>0</sub>, and the wave-front speed. In addition, isoplanatic angle θ<sub>0</sub> is determined from scintillation, making the characterization of turbulence with the GSM almost complete. We describe the instrument and make a detailed analysis of its performance and accuracy. Several site-testing campaigns have been conducted with the GSM: at La Silla (Chile), Oukaïmeden (Morocco), Maidanak (Uzbekistan), and Cerro Pachon and Cerro Paranal (Chile). The main results of these campaigns are presented and discussed.
© 2000 Optical Society of America
(010.1080) Atmospheric and oceanic optics : Active or adaptive optics
(010.1290) Atmospheric and oceanic optics : Atmospheric optics
(010.1300) Atmospheric and oceanic optics : Atmospheric propagation
(010.1330) Atmospheric and oceanic optics : Atmospheric turbulence
(010.1350) Atmospheric and oceanic optics : Backscattering
Aziz Ziad, Rodolphe Conan, Andrei Tokovinin, François Martin, and Julien Borgnino, "From the Grating Scale Monitor to the Generalized Seeing Monitor," Appl. Opt. 39, 5415-5425 (2000)