MATLAB
`B = BeamIrradianceCovariance(alpha,d,Atm,wvl,W0,F0)`

Computes the irradiance covariance for a beam wave given turbulence multiplier alpha, point spacings d, atmospheric modeling data in Atm, and wavelength in wvl. In this calculation, the light propagates from the target to the platform. Uses the weak turbulence assumption. Use with caution - function is numerically unstable.

 Parameters Description alpha [scalar] Turbulence strength multiplier. d [vector] Separation of the points in the aperture plane (m). Atm [struct] Atmospheric modeling structure from AtmStruct. wvl [scalar] Optical wavelength (m). W0 [scalar] 1/e radius of the source field (m). F0 [scalar] Radius of curvature of the source field (m).
 Return Values Description B [vector] Irradiance covariance value EXAMPLES; > alpha 1; > wvl 0.5e-6; > G SimpleGeom(0, 2e4, 0); > Atm AtmStruct(G, 100, 'Cn2', 'HV57'); > d linspace(0, sqrt(Atm.L/(2*pi/wvl))*4, 10); > W0 0.5; > F0 inf; > B BeamIrradianceCovariance(alpha, d, Atm, wvl, W0, F0); Irradiance covariance for turbulence multiplier of 1, wavelength 500 nm, focused Gaussian source with beam radius 50 cm at 20 km propagating straight down, pupil-plane separations d, and atmospheric model Atm.

• L. C. Andrews and R. L. Phillips, Laser Beam Propagation through Random Media, 2nd ed. Bellingham, Wash.: SPIE Press, 2005.

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