AtmoPathSWP uses spherical wave propagation (converging / diverging propagation grids) to model optical propagation through atmospheric turbulence. AtmoPathSWP may also be used for planar wave propagation by setting propdxyPlat and propdxyTarg to the same value, i.e., propdxyPlat = propdxyTarg = propdxy. The atmosphere is modeled using multiple "phase screens", typically 5-20, distributed along the propagation path. Each phase screen represents the cumulative optical path differences for a slab of atmosphere, and in between phase screens we perform vacuum propagations, using a two-step FFT propagator. The details of the path model (number and placement of screens, turbulence strengths, inner scale, etc.) are specified by "atmosphere specification" (an object of type AcsAtmSpec). Atmosphere specifications can be created using TurbTool, and for certain common cases (e.g. uniformed turbulence, or scaled Clear1) we have also provided a more convenient function call interface. The phase screen dimensions are automatically calculated to span the propagation mesh at each screen location. If the specified bounds should be exceeded due to wind dragging, each screen will be "scrolled" as necessary. AtmoPathSWP is a composite system class, consisting of a GeneralAtmosphere2 and two PropagationControllers, and provides a simplified interface for propagation modeling options, which assumes that the same modeling options will be used in both propagation directions, including using planar or spherical reference waves with the same grid size and spacings and the defaults for point source and speckle modeling, with no spatial filtering or absorbing boundaries. If this is not what is desired, the user may wish to work with GeneralAtmosphere2 and PropagationController directly.

There is the option to remove tilt over a specified area from individual phase screens, with the area specified by a diameter.
Phase screens are available as output as a nscreen by 11+nxy*nxy array. The header of 11 data values before the nxy*nxy phase values for each screen is set in compPhaseScreen() in AcsPhaseScreen.cpp as:
propGrid->nx();
propGrid->ny();
propGrid->dx();
propGrid->dy();
propGrid->xCenter()-xtw;
propGrid->yCenter()-ytw;
distance;
rateX;
rateY;
xtw;
ytw;

Parameters
atmSpec	AcsAtmSpec	Specifies all the properties of the atmospheric path model: range, turbulence distribution, number of phase screens, etc.	AcsAtmSpec()
atmoSeed	int	Random number seed for atmospheric phase screens	-123456789
propnxy	int	Propagation mesh dimension (for both x & y)	propnxy
propdxyPlat	float	Propagation mesh at platform (for both x & y)	propdxyPlat
propdxyTarg	float	Propagation mesh at target (for both x & y)	propdxyTarg
superApDiameterOut	float	Used in modeling point sources and surface speckle; defines a circular region at the target plane which in vacuum would be uniformly illuminated	propnxy*propdxyTarg/2.0f
edgeSigmaOut	float	Used in modeling point sources and surface speckle; defines a gaussian round off at the edge of the superaperture	propdxyTarg
superApDiameterRet	float	Used in modeling point sources and surface speckle; defines a circular region at the platform plane which in vacuum would be uniformly illuminated	propnxy*propdxyPlat/2.0f
edgeSigmaRet	float	Used in modeling point sources and surface speckle; defines a gaussian round off at the edge of the superaperture	propdxyPlat
removeTilt	bool	Remove tilt from phase screens	false
diam	float	Beam diameter for tilt removal fit (m)	propnxy*propdxyPlat
useDispersion	bool	Use atmospheric dispersion calculations	false
nominalWavelength	float	Nominal wavelength (m) for dispersion calculations	0.0
Inputs
incomingIncident	WaveTrain	Describes all light incident from the "incoming" direction	WaveTrain()
outgoingIncident	WaveTrain	Describes all light incident from the "outgoing" direction	WaveTrain()
Outputs
incomingTransmitted	WaveTrain	Describes all light transmitted in the "incoming" direction
outgoingTransmitted	WaveTrain	Describes all light transmitted in the "outgoing" direction
phaseScreen	Array<float>	Phase screens as a nscreen by 11+nxy*nxy array
Subsystems
GeneralAtmosphere2    generalAtmo atmSpec   AcsAtmSpec    atmSpec randomSeed   int    atmoSeed gridPlatform   GridGeometry    gwoom(propnxy,propdxyPlat) gridTarget   GridGeometry    gwoom(propnxy,propdxyTarg) dxy   float    fmin(propdxyPlat,propdxyTarg) locFlag   int    0 removeTilt   bool    removeTilt diam   float    diam   PropagationController    propagationcontroller0 targetGrid   GridGeometry    grid_with_origin_on_mesh(propnxy,propnxy,propdxyTarg,propdxyTarg) xReferenceFocus   float    Rref(propdxyTarg,propdxyPlat,-atmSpec.pathLength()) yReferenceFocus   float    Rref(propdxyTarg,propdxyPlat,-atmSpec.pathLength()) oneTimeSpatialFilter   constFilter&    NullFilter() spatialFilter   constFilter&    NullFilter() absorbingBoundary   constFilter&    NullFilter() pointSourceModel   PointSourceModel    DEFAULT_PSM speckleModel   SpeckleModel    DEFAULT_SM superApDiameter   float    superApDiameterRet edgeSigma   float    edgeSigmaRet useDispersion   bool    useDispersion nominalWavelength   float    nominalWavelength   PropagationController    propagationcontroller targetGrid   GridGeometry    grid_with_origin_on_mesh(propnxy,propnxy,propdxyPlat,propdxyPlat) xReferenceFocus   float    Rref(propdxyPlat,propdxyTarg,atmSpec.pathLength()) yReferenceFocus   float    Rref(propdxyPlat,propdxyTarg,atmSpec.pathLength()) oneTimeSpatialFilter   constFilter&    NullFilter() spatialFilter   constFilter&    NullFilter() absorbingBoundary   constFilter&    NullFilter() pointSourceModel   PointSourceModel    DEFAULT_PSM speckleModel   SpeckleModel    DEFAULT_SM superApDiameter   float    superApDiameterOut edgeSigma   float    edgeSigmaOut useDispersion   bool    useDispersion nominalWavelength   float    nominalWavelength Connections propagationcontroller0.incident   <<=   incomingIncident propagationcontroller.incident   <<=   outgoingIncident incomingTransmitted   <<=   generalAtmo.incomingTransmitted outgoingTransmitted   <<=   generalAtmo.outgoingTransmitted phaseScreen   <<=   generalAtmo.phaseScreen generalAtmo.incomingIncident   <<=   propagationcontroller0.transmitted generalAtmo.outgoingIncident   <<=   propagationcontroller.transmitted
Last Saved: Fri Feb 22 10:45:06 MST 2008 by TVE version 2007B