SUBROUTINE  VISNP (PH,TH,JP,IT,NP,NT,O)

C     [NEAREST POINT]
C     DETERMINE THE COORDINATES OF THE LINE OF SIGHT JOINING THE
C     OBSERVER TO THE CENTER OF THE SPHERICAL COORDINATES.
C     (PH,TH)  SURFACE COORDINATES OF NEAREST POINT
C     (JP,IT)  INDICES OF NEAREST POINT
C     (NP,NT)  RANGE OF PHI, THETA INDICES
C     O(3,3)   ORTHOGONAL MATRIX DEFINING ROTATION
C     [16-JUN-74]

      DIMENSION   O(3,3)

      O31=O(3,1)
      O32=O(3,2)
      PH=ATAN2(O32,O31)
      IF (PH.LT.0.0) PH=6.28318+PH
      RH=SQRT(O31*O31+O32*O32)
      TH=ATAN2(RH,O(3,3))
      JP=1+IFIX(0.5+(FLOAT(NP)*PH)/6.28318)
      IT=MIN0(MAX0(IFIX(1.5+(TH*FLOAT(NT-1))/3.14159),1),NT)
      RETURN

      END