In order to solve our shock wave equations the initial flyer density, pressure and velocity are required. Since our acceleration is few femtoseconds the density does not change by more than 20% (w2vTt/l, where t is the acceleration time before impact of the order of few femtosecond, l is the initial foil thickness and vT is the thermal plasma velocity of the flyer usually less than 109 cm/s). Furthermore, the initial density could be measured using an X-ray pulse created by a secondary laser beam. Regarding the initial pressure it was calculated (Eliezer et al., 2013) that it is negligible for the shock wave pressures under consideration which are larger than 1012 bars upon impact. The flyer velocity can be measured experimentally using the relativistic Doppler Effect.