  Radiative shocks (RS) are complex phenomena which are ubiquitous in
astrophysical environments. The study of such hypersonic shocks in the
laboratory, under controlled conditions, is of primary interest to understand
the physics at play and also to check the ability of numerical simulations to
reproduce the experimental results. In this context, we conducted, at the
Prague Asterix Laser System facility (PALS), the first experiments dedicated to
the study of two counter-propagating radiative shocks propagating at non-equal
speeds up to 25-50 km/s in noble gases at pressures ranging between 0.1 and 0.6
bar. These experiments highlighted the interaction between the two radiative
precursors. This interaction is qualitatively but not quantitatively described
by 1D simulations. Preliminary results obtained with XUV spectroscopy leading
to the estimation of shock temperature and ion charge of the plasma are also
presented.
