BeaconD0

MATLAB

d0 = BeaconD0(alpha,lambda,Geom,Lb,Atm)

Description

Computes the section size of a laser guide star beacon (d0) given turbulence assumptions, propagation geometry, and wavelength. Output is appropriate for computing residual phase variance for compensation from laser guide star beacon as $(D/d0)^{5/3}$. Assumes the target object is at a finite range as specified by Geom. Hence propagation calculations are made using spherical wave analysis. Returns NaN if propagation path intersects earth surface.

Parameters

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 structure 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)
Lb [scalar]	Slant range of beacon (m)
Atm [struct/string]	Atmospheric modeling parameters. Can be a structure from AtmStruct or a turbulence profile model to be used.

Return Values

Return Values	Description
d0 [vector]	Laser guide star beacon section size (m)

References

Tyler, G. A. et al., "Adaptive Optics: Theory and Applications," Tech Rep. AFRL-DE-PS-TR-1998-1054, Air Force Research Laboratory, Directed Energy Directorate, Sec 2.5 (1999).

Examples

>> G = GeomStruct;

>> Atm = AtmStruct;

>> d0 = BeaconD0(1,550e-9,G,Atm.L/2,Atm)

Geom and Atm must have same values for hp, ht, and rd.

>> d0 = BeaconD0(1,550e-9,G,Atm.L,'HV57')

>> d0 = BeaconD0(1,550e-9,0,12000,0,24000,'HV57')