A method for determining the coefficients of an asymptotic

-expansion, known as Luneburg-Kline expansion, from bandlimited scattering data is presented. The coefficients are derived from the output signals of an orthogonal filter. The method is applicable to calculate geometric quantities as principal radii or principal directions of curvature of simple scatterers. Furthermore early parts of transient backscattered signals can be analyzed, e.g., to reconstruct the early ramp or impulse response.