[Function] Air Mass Calculation

Function AirMass, Angle
; ********************************************************
; IDL Function to calculate air mass ; *********************************************************
; Air Mass = COS(Sun Zenith Angle or Sensor View Angle)
;
; 2008. 10. 4
; WRITTEN BY Kwon H. Lee (kwonho.lee@gmail.com)
;=============================================
XG=Angle*!dtor
IF(Angle GE 60.0) THEN begin
AMass=COS(XG)+0.50572*((6.07995+90.0-Angle)^(-1.6364))
endif ELSE begin
AMass=COS(XG)
ENDelse
return, Amass
end