is the name of the body-fixed, body-centered
               reference frame associated with the target body. The
               input surface point `spoint' and the output vector
               `srfvec' are expressed relative to this reference
               frame. The string `fixref' is case-insensitive, and
               leading and trailing blanks in `fixref' are not
               significant.

               [1,c4] = size(fixref); char = class(fixref)

                  or

               [1,1] = size