Experimental investigation of scaling laws for the noise-equivalent angle due to speckle and scintillation

In this paper, we investigate the scaling laws associated with jitter error in active imaging systems for long-range applications. Coherent effects such as speckle (induced by rough-surface scattering) and scintillation (induced by extended-volume turbulence) contribute to line-of-sight jitter and reduce system performance. A key concern is estimating centroid jitter in the focal plane that is indistinguishable from noise. Practitioners typically quantify this tracking error by the noise-equivalent angle (NEA). In this work, we construct a scaled laboratory experiment that generates the coherent effects of speckle and scintillation. Using this setup, we independently validate the scaling laws for NEA due to speckle and scintillation in addition to investigating the coupling between these two contributions. When both speckle and scintillation are present, we observe weak coupling between the two contributions. As a result, the quadrature sum of the individual NEA terms provides a good estimate of the total jitter error. These results, at large, enable more accurate estimations of tracking errors in active imaging systems operating through extended-volume turbulence where both speckle and scintillation are present.