  Only weakly interacting, neutrinos are the principal messengers reaching us
from the center of a supernova. Terrestrial neutrino telescopes, such as SNO
and SuperKamiokande, can provide precious information about the processes in
the core of a collapsing and exploding star. But the information about the
supernova that a neutrino detector can supply, is restricted by the fact that
little experimental data on the neutrino-nucleus cross sections exists and by
the uncertainties in theoretical calculations. In this letter, we propose a
novel procedure that determines the response of a target nucleus in a
supernova-neutrino detector directly, by using low-energy beta-beams. We show
that fitting 'synthetic' spectra, constructed by taking linear combinations of
beta-beam spectra, to the original supernova-neutrino spectra reproduces the
folded differential cross sections very accurately. Comparing the response in a
terrestrial detector to these synthetic responses provides a direct way to
determine the main parameters of the supernova-neutrino energy-distribution.
