Low-elevation transmission measurements at EOPACE III. Scintillation effects

This paper concerns the effect of scintillation on the detection range of infrared sensors, where frame rate appears to play an important role. During EOPACE scintillation measurements were carried out over the Monterey and San Diego Bay. For this purpose 2 kinds of sources were used, either a source, modulated with 1000 Hz, or a DC searchlight source. The detector was a silicon detector with a narrow bandfilter around 0.85 tim. The results show that scintillation is always present, even when locally the air to sea temperature difference (ASTD) is close to zero. This indicates that large ASTD variations may occur along the measurement path. The magnitude of the scintillation agrees reasonably well with the theory. This means a big advantage for high frame rate sensors in comparison with low frame rate sensors for detection of point targets at low elevation.