Direct neutrino mass measurements

Direct neutrino mass measurements are based on high precision spectroscopy studies close to the kinematic end-point of low-energy beta-emitters such as H-3 and Re-187. Relying only on energy-momentum conservation in beta-decay, they offer the only model-independent method to measure the absolute nu-mass scale with sub-eV sensitivity. The two most sensitive detection principles, electrostatic retarding spectrometers and microbolometers, are complementary to each other, and two experiments are currently being prepared to explore nu-masses down to m(nu) = 200 meV. beta-spectroscopy will thus allow to constrain the role of neutrino hot dark matter in structure formation, as well as to explore the parameter region of nu-mass scenarios with quasi-degenerate pattern. The MARE project will investigate the beta-decay of Re-187 with bolometers based on metallic Re and AgReO4 in a two-staged approach: in a phase-I set-up a sensitivity of m(nu) = 2 eV is expected, forming the basis for a later sub-eV phase-H. The Karlsruhe Tritium Neutrino (KATRIN) experiment is currently being set-up on the site of Tritium Laboratory at KIT. The experiment will combine an ultra-luminous windowless gaseous tritium source with a high resolution electrostatic spectrometer and offer an unprecedented precision in beta-decay studies, pushing this technique to its technological limits. First KATRIN measurements with H-3 after successful system integration are expected for mid-2011. This contribution gives a status report and outlook for both experiments and discusses the impact of direct nu-mass experiments on astroparticle physics.