t indicate
                the Moon is the target body.

                The target and observer define a position vector
                whose position component points from the observer
                to the target.

                [1,c1] = size(target), char = class(target)

                   or

                [1,1] = size(target); cell = class(target)

      et        the ephemeris time(s), expressed as seconds past J2000
                TDB, at which the position of the target body relative to
   