C     -*-fortran-*-
C     RAIN ATTENUATION PREDICTION ACCORDING TO YAMADA ET AL.
C     RADIO SCIENCE, VOL.22, NO.6, NOV.1987
C     *********************
      REAL LAT, LS, L0, LE
C     PARAMETER INPUTS
C
C     INPUT FROM RAIN CLIMATE CONTOURS
      WRITE (6,*) "0.01% PROBABLE RAIN RATE (MM/HR.)?" 
      READ (5,*) R01
C     INPUT aR^b COEFFICIENTS FOR FREQUENCY AND POLARIZATION
      WRITE (6,*) "aR^b COEFFICIENTS, a,b?"
      READ (5,*) A,B
C     INPUT SITE INFORMATION
      WRITE (6,*) "SITE ALTITUDE (KM), LATITUDE (DEG), SATELLITE ELEVATION ANGL
     $E (DEG)?"
      READ (5,*) HS,LAT,EL
C
C     **********************
C     PRELIMINARY CALCULATIONS
C
      EL=EL*3.14159/180.0
      AS=A*R01**B
      WRITE (6,*) "0.01% PROBABLE SPECIFIC ATTEN = ", AS, " DB/KM"
      IF (LAT-36.0) 2,2,3
   2  H=4.0
      GO TO 4
   3  H=4.0-0.075*(LAT-36.0)
      WRITE (6,*) "RAIN HEIGHT = ", H, "KM"
   4  LS=(H-HS)/SIN(EL)
      WRITE (6,*) "SLANT PATH THROUGH RAIN = ", LS, "KM"
      L0=35.0*EXP(-0.015*R01)
      WRITE (6,*) "CHARACTERISTIC RAIN CORRELATION DIST = ", L0, "KM"
      LE=LS/(1+LS*COS(EL)/L0)
      WRITE (6,*) "EFFECTIVE RAIN PATH = ", LE, "KM"
      A01=AS*LE
      WRITE (6,*) "0.01% PROBABLE ATTENUATION = ", A01, "DB"
C
C     ***********************
C     INTERACTIVE CALCULATION
C
  10  WRITE (6,*) "PERCENT PROBABILITY THE CALCULATED ATTENUATION WILL
     XBE EXCEEDED ? 0 ENDS PROGRAM"
      READ (5,*) P
      IF (P) 30,30,40
  40  A=0.12*A01*(P**(-0.546-0.043*ALOG(P)/ALOG(10.0)))
      WRITE (6,*) "ATTENUATION =", A, "DB"
      GO TO 10
  30  END