def _keplerian_to_keplerian_circular(cls, coord, center):
        """Conversion from Mean Keplerian to Keplerian near-circular elements
        """
        a, e, i, Ω, ω, ν = coord

        ex = e * cos(ω)
        ey = e * sin(ω)
        u = ω + ν

        return np.array([a, ex, ey, i, Ω, u], dtype=float)