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diff --git a/src/slalib/ds2c6.f b/src/slalib/ds2c6.f
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+      SUBROUTINE sla_DS2C6 (A, B, R, AD, BD, RD, V)
+*+
+*     - - - - - -
+*      D S 2 C 6
+*     - - - - - -
+*
+*  Conversion of position & velocity in spherical coordinates
+*  to Cartesian coordinates
+*
+*  (double precision)
+*
+*  Given:
+*     A     dp      longitude (radians)
+*     B     dp      latitude (radians)
+*     R     dp      radial coordinate
+*     AD    dp      longitude derivative (radians per unit time)
+*     BD    dp      latitude derivative (radians per unit time)
+*     RD    dp      radial derivative
+*
+*  Returned:
+*     V     dp(6)   Cartesian position & velocity vector
+*
+*  P.T.Wallace   Starlink   10 July 1993
+*
+*  Copyright (C) 1995 Rutherford Appleton Laboratory
+*-
+
+      IMPLICIT NONE
+
+      DOUBLE PRECISION A,B,R,AD,BD,RD,V(6)
+
+      DOUBLE PRECISION SA,CA,SB,CB,RCB,X,Y,RBD,W
+
+
+
+*  Useful functions
+      SA=SIN(A)
+      CA=COS(A)
+      SB=SIN(B)
+      CB=COS(B)
+      RCB=R*CB
+      X=RCB*CA
+      Y=RCB*SA
+      RBD=R*BD
+      W=RBD*SB-CB*RD
+
+*  Position
+      V(1)=X
+      V(2)=Y
+      V(3)=R*SB
+
+*  Velocity
+      V(4)=-Y*AD-W*CA
+      V(5)=X*AD-W*SA
+      V(6)=RBD*CB+SB*RD
+
+      END