n a state in planetographic coordinates 
 
      ( lon, lat, alt, dlon, dlat, dalt ) 
 
   the velocity in rectangular coordinates is given by the matrix 
   equation: 
 
                  t          |                                  t 
      (dx, dy, dz)   = jacobi|              * (dlon, dlat, dalt) 
                             |(lon,lat,alt) 
 
 
   This routine computes the matrix  
 
            | 
      jacobi| 
            |(lon,lat,alt) 
 
 
   In the planetographic coordinate system, longitude is 