  In order to understand the r-process nucleosynthesis, we suggest precision
required for mass and beta-decay half-life measurements planned at future
RI-beam facilities. To satisfy a simple requirement that we put on nuclear
model predictions, it is concluded that the detectors for the mass measurements
must have a precision of 1sigma ~< 250 keV, and that the detectors for the
half-life measurements demand a precision of 1sigma ~< 0.15 ms. Both the above
precisions are required at the neutron richness of A/Z = 3.0 at the N=82 shell
closure and A/Z = 2.9 at the N=50 shell closure. For the doubly magic nuclide
78Ni, a precision of 1sigma ~< 300 keV and 1sigma ~< 5 ms are required,
respectively, for mass and half-life measurements. This analysis aims to
provide a first rough guide for ongoing detector developments.
