code: def vproj(a, b):
      
      a = stypes.toDoubleVector(a)
      b = stypes.toDoubleVector(b)
      vout = stypes.emptyDoubleVector(3)
      libspice.vproj_c(a, b, vout)
      return stypes.cVectorToPython(vout)
docs: Find the projection of one vector onto another vector.
  
      http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/vproj_c.html
  
      :param a: The vector to be projected. 
      :type a: 3-Element Array of floats
      :param b: The vector onto which a is to be projected. 
      :type b: 3-Element Array of floats
      :return: The projection of a onto b.
      :rtype: 3-Element Array of floats