No abstract

The scintillation pattern from a single star can be utilized to provide information on the refractive turbulence along the line of sight. Instruments that provide refractive turbulence parameters are the isoplanometer and the stellar scintillometer. Attention is drawn to the fact that the National Oceanic and Atmospheric Administration theoretical treatment and implementation of the stellar scintillometer is incomplete. The theory is corrected for spectral effects and finite aperture. A comparison is made of simultaneously obtained isoplanometer values and stellar scintillometer-derived values for isoplanatic angle. The measurements are obtained from an electro-optical/meteorological experiment conducted at Pennsylvania State University in April and May 1986. An atmospheric drop-off model is used to extrapolate the scintillometer measurements beyond the heights probed. Agreement between the two instruments is significantly improved after the appropriate corrections are applied to the scintillometer data. These data were obtained during widely varying meteorological conditions that provided the opportunity for comparisons over a wide range of isoplanatic angles (3 to 14 ,rad).Over the 5 days that data were obtained, relative percent departures of mean isoplanatic angles derived from the corrected stellar scintillometer are within 10% of the mean isoplanometer isoplanatic angle values. The uncorrected departures range from 16% to 24%.

The possibility of obtaining vertical profiles of refractive turbulence C' using an orbiting monochromatic light source is examined. The method employs spatial and temporal filtering of the observed scintillation pattern arising from density fluctuations in the atmosphere to measure C2. The impact of atmospheric motion on the method is discussed along with ways to mitigate its effect. Single and array receiver configurations are examined and the multiple response problem inherent in array configurations is corrected by tuning the individual array elements to the array response. The method is expected to be significantly better than the existing stellar scintillometer method.