MATLAB
`Theta0 = SphericalTheta0(alpha,lambda,Geom,Atm)`

Computes the spherical wave isoplanatic angle given turbulence assumptions, propagation geometry, and wavelength. Returns NaN if propagation path intersects earth surface.

 Parameters Description alpha [vector] Multiplier on turbulence model lambda [scalar] Wavelength of laser (m) Geom [struct/list] Geometry parameters. Can be a structure from GeomStruct or a comma separated list of (...,hp,ht,rd) - not required if Atm is a struct from AtmStruct hp [scalar] Altitude of transmit/receive platform (m) ht [scalar] Altitude of target (m) rd [scalar] Downrange of target along spherical earth surface (m) Atm [struct/string] Atmospheric modeling parameters. Can be a structure from AtmStruct or a turbulence profile model to be used.
 Return Values Description Theta0 [vector] Spherical wave isoplanatic angle (rad)

• Fried, D. L. "Anisoplanatism in Adaptive Optics." J. Opt. Soc. Am. 72, 52-61 (1982).

>> theta0 = SphericalTheta0(1.0,1.0e-6,AtmStruct)

• Compute theta0 at 1 micron using the turbulence model in the input Atm struct.
>> theta0 = SphericalTheta0(2.0,1.0e-6,GeomStruct,AtmStruct)

• Compute theta0 scaling the input turbulence model by a factor of 2 in addition to any turbulence multiplier already in the Atm struct. If Geom and geometry in Atm are not consistent, Atm will be updated.
>> theta0 = SphericalTheta0(2.0,1.0e-6,GeomStruct, ...

{'HufnagelValley',15,1e-15})

• Compute theta0 scaling the input turbulence model by a factor of two. To pass additional parameters to the model, pass the model name and parameters in a cell array.
>> theta0 = SphericalTheta0(1.0,1.0e-6,10,3000,10000,'HV57')

• Compute theta0 passing geometry as a list with a continuous turbulence model.

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