Generalized SCIDAR Measurements at San Pedro Mártir. I. Turbulence Profile Statistics

Abstract

We present the results of monitoring optical-turbulence profiles at San Pedro Mártir, Mexico, during 11 nights in 1997 March and April, and 16 nights in 2000 May. The data were collected using the generalized scintillation detection and ranging (SCIDAR) technique from Nice University at the 1.5 and 2.1 m telescopes. A total of 6414 turbulence profiles were measured and statistically analyzed. The principal results are as follows: the seeing produced by the turbulence in the first 1.2 km at the 1.5 m and 2.1 m telescopes, not including turbulence inside the domes, have median values of 0″.63 ± 0″.01 and 0″.44 ± 0″.02, respectively. The dome seeing at those telescopes have median values of 0″.64 ± 0″.01 and 0″.31 ± 0″.02. The median values of the seeing produced above 1.2 km and in the whole atmosphere are 0″.39 ± 0″.01 and 0″.71 ± 0″.01. The isoplanatic angle for full-correction adaptive optics has a median value of 1″.87 ± 0″.04. The decorrelation time (defined as the time lag for which the temporal correlation drops to 50%) of the turbulence strength at altitudes below and above 16 km above sea level is approximately equal to 2 and 0.5 hr, respectively. The isoplanatic-angle decorrelation time is estimated to be equal to 2 hr. The turbulence above ∼8 km remained notably calm during nine consecutive nights, which is encouraging for adaptive optics observations at the site. The results obtained here places San Pedro Mártir among the best suited sites for installing next-generation optical telescopes.