Book Description

A stellar scintillometer measures the variance of stellar intensity for a first magnitude or greater star. This variance can be converted, by the use of spatial filters, into a profile of (c sub n) -sq, the index of refraction structure constant, for 7 different altitudes or levels. The (c sub n) -sq values are not entirely instrument independent because there will be some overlap in the weighting functions used to separate the spatial frequencies. It is usually assumed that readings from levels 1, 4, and 7 are instrument independent. When linear correlation coefficients are calculated between levels for (c sub n) -sq and Log (c sub n) -sq of this data set, results obtained seem to contradict the above stated assumption. Much less correlation is observed when calculated on a nightly basis. In fact, some nightly coefficients are significantly negative, which could not be due to weighting function overlap. We have investigated other mechanisms which could lead to a high degree of correlation across the entire data set. During the measurement program, atmospheric conditions changed from evening to evening. For example, the jet stream passed through several times affecting the entire altitude range of the scintillometer. Correlation studies do not indicate that, except for low lying adjacent levels, (c sub n) -sq values obtained using the scintillometer are instrument dependent.