We present the reconstruction of neutrino flavor ratios at astrophysical
sources. For distinguishing the pion source and the muon-damped source to the
3σ level, the neutrino flux ratios,
R≡ϕ(νμ)/(ϕ(νe)+ϕ(ντ)) and
S≡ϕ(νe)/ϕ(ντ), need to be measured in accuracies better
than 10%.Comment: 3 pages, 8 figures. Talk presented by T.C. Liu in ERICE 2009, Sicily