  The KATRIN experiment in Karlsruhe Germany will monitor the decay of tritium,
which produces an electron-antineutrino. While the present upper bound for its
mass is 2 eV/$c^2$, KATRIN will search down to 0.2 eV$/c^2$. If the dark matter
of the galaxy cluster Abell 1689 is modeled as degenerate isothermal fermions,
the strong and weak lensing data may be explained by degenerate neutrinos with
mass of 1.5 eV$/c^2$. Strong lensing data beyond 275 kpc put tension on the
standard cold dark matter interpretation. In the most natural scenario, the
electron antineutrino will have a mass of 1.5 eV/$c^2$, a value that will be
tested in KATRIN.
