Atm = AtmStruct(Geom,Nscreens,...

Atm = AtmStruct(Geom,x,dx,...

Generates a structure with atmospheric model data for a specified laser propagation path, with modeling assumptions as specified in the calling sequence. Structure may contain turbulence, absorption, scattering, and temperature model data for the laser path altitude corresponding to the input geometry. Assumes specified atmospheric models are available as altitude-dependent functions (with arbitrary parameters), where altitude is the first input to the function. Data in these structures is appropriate for use in wave-optics simulation or propagation analysis calculations.

Geom [struct/list] 
Geometry parameters. Can be a structure from GeomStruct or a comma separated list of (hp,ht,rd,...) 
hp [scalar] 
Platform altitude (m) 
ht [scalar] 
Target altitude (m) 
rd [scalar] 
Downrange along spherical earth surface (m) 
NScreens [scalar] 
(Optional) Number of equal thickness phase screens. Screens are spaced symmetrically about the midpoint of the propagation path. For a continuous model use NScreens=Inf 
x [vector] 
(Optional) Path-normalized screen location in range 0<=x<1. Passing x=1 or x=[1] will result in a single phase screen placed at the midpoint of the propagation path. For single screen at the target, use x=[0.9999] 
dx [vector] 
(Optional) Path-normalized screen thickness. Must be the same size as x if passed. 
MaxAlt [scalar] 
(Optional) The maximum altitude over which the discrete atmosphere should be evaluated (m). Defaults to Inf. At altitudes above MaxAlt, the model evaluations are set to 0. NScreens, x, and dx are interpreted as being over the path where altitude is less than MaxAlt. MUST BE SCALAR. 
xRange [vector] 
(Optional) The normalized ranges over which the atmospheric models are to be computed. MaxAlt is a shortcut that will compute xRange for the path. The user can also manually specify the ranges. If both MaxAlt and xRange are specified, xRange will be set by taking the max of xRange(1) and the min of xRange(2). MUST BE 1x2.
OPTIONAL INPUTS FOR ATMOSPHERIC MODELS: The remaining inputs are all optional, and are used to set values of model data in the Atm structure of 13 types: 'Cn2' (turbulence strength), 'Abs' (absorption coefficient), 'Scat' (scattering coefficient), 'Temp' (temperature), 'Wind' (natural wind), 'WindHeading' (natural wind direction), 'Ext' (extinction), 'Press' (atmospheric pressure), 'Dens' (atmospheric density), 'Lin' (inner scale for turbulence), 'Lout' (outer scale for turbulence), 'RH' (relative humidity), and 'DewPt' (dew point). Model data is generated by calls to existing functions of the form ModelName(h,P1...PN). Any, all, or none of the models may be set, depending upon calling sequence. If a particular type of model is specified twice, the last specification will be used in the Atm structure. If an error is encountered in evaluating the model function, the Atm fields will not be set for the specified model type.
ModelType [string] 
(Optional) Identifier for type of atmospheric model. Supported model types are 'Cn2', 'Abs', 'Scat', 'Temp', 'Wind', 'WindHeading', 'Ext', 'Press', 'Dens' 'Lin', 'Lout', 'RH', and 'DewPt' affecting the corresponding field in the Atm structure. 
ModelName [string] 
(Required if specifying ModelType) Function to be evaluated in setting the model values. Must correspond to a function on the Matlab path with calling sequence ModelName(h,P1...PN). For available models type "help AtmModels." To input measured data for any model, use "NoEval" for the ModelName and the data values - in vector form" for the input parameter. 
Parameter values for the function ModelName, as required by the specified function 
Return Values
Return Values 
Atm [struct] 
Structure containing turbulence screen parameters 
Atm.hp [scalar] 
Altitude of transmit/receive platform (m) [scalar] 
Altitude of target (m) 
Atm.rd [scalar] 
Downrange to target along curved earth surface (m) 
Atm.L [scalar] 
Slant range from platform to target (m) 
Atm.LatLong [struct] 
Structure of geometry information used to create/recreate an Atm structure 
Atm.MaxAlt [scalar] 
Max Alt over which the models are evaluated (m) 
Atm.xRange [vector] 
Normalized slant ranges at the beginning and end of the atmosphere. Can be set by MaxAlt or by specifying xRange. 
Atm.z [vector] 
Phase screen distances from transmitter (m) [vector] 
Phase screen thicknesses (m) 
Atm.h [vector] 
Altitude of each phase screen above earth surface (m) 
Atm.Cn2 [vector] 
(Optional) Cn2 values for the phase screens (${m}^{-2/3}$) 
Atm.Cn2Eval [cell] 
(Optional) Turbulence model evaluation 
Atm.Abs [vector] 
(Optional) Absorption coefficients for the phase screens (1/m) 
Atm.AbsEval [cell] 
(Optional) Absorption model evaluation 
Atm.Scat [vector] 
(Optional) Scattering coefficients for the phase screens (1/m) 
Atm.ScatEval [cell] 
(Optional) Scattering model evaluation 
Atm.Temp [vector] 
(Optional) Temperature values for the phase screens (K) 
Atm.TempEval [cell] 
(Optional) Temperature model evaluation 
Atm.Wind [vector] 
(Optional) Natural wind speed values for the phase screens (m/s) 
Atm.WindEval [cell] 
(Optional) Natural wind model evaluation 
Atm.WindHeading [vector] 
(Optional) Natural wind heading for the phase screens (deg from North) 
Atm.WindHeadingEval [cell] 
(Optional) Natural wind heading model evaluation 
Atm.VerticalWind [vector] 
(Optional) Natural vertical wind 
Atm.VerticalWindEval [cell] 
(Optional) Natural vertical wind model evaluation 
Atm.Ext [vector] 
(Optional) Extinction coeff. values for the phase screens (1/m) 
Atm.ExtEval [cell] 
(Optional) Extinction model evaluation 
Atm.Press [vector] 
(Optional) Atmospheric pressure values for the phase screens (Pa) 
Atm.PressEval [cell] 
(Optional) Pressure model evaluation 
Atm.Dens [vector] 
(Optional) Atmospheric density values for the phase screens (${kg}/{m}^3$) 
Atm.DensEval [cell] 
(Optional) Density model evaluation 
Atm.Lin [vector] 
(Optional) Turbulence inner scale values for the phase screens (m) 
Atm.LinEval [cell] 
(Optional) Inner scale model evaluation 
Atm.Lout [vector] 
(Optional) Turbulence outer scale for the phase screens (m) 
Atm.LoutEval [cell] 
(Optional) Outer scale model evaluation 
Atm.RH [vector] 
(Optional) Relative humidity for the phase screens (%) 
Atm.RHEval [cell] 
(Optional) Relative humidity model evaluation 
Atm.DewPt [vector] 
(Optional) Dew point for the phase screens (K) 
Atm.DewPtEval [cell] 
(Optional) Dew point model evaluation 

>> Atm = AtmStruct(3000,10000,50000,Inf,'Cn2','Clear1Night') 

  • Continuous Atm with turbulence specified by Clear1Night
>> Atm = AtmStruct(GeomStruct,20,'Abs','LogScaling',10,1e-5,3000) 

  • Discrete Atm with 20 equally spaced screens which uses a log scaling for the absorption profile
>> Atm = AtmStruct(GeomStruct,[.25 .75],[.5 .5],'Cn2','HV57') 

  • Discrete Atm with 2 screens at 0.25 and 0.75 times the slant range with thickness equal to half the slant range

See Also
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