  It is in principle possible to measure directly the electron neutrino mass
(or masses and mixing angles) in weak electron-capture decays. The optimal
nuclide in this respect is $^{163}$Ho. The favoured experimental technique,
currently pursued in various experiments (ECHo, HOLMES and NuMECS) is
"calorimetric". The calorimetric energy spectrum is a sum over the unstable
vacant orbitals, or "holes", left by the electrons weakly captured by the
nucleus. We discuss the current progress in this field and analize the
preliminary data. Our conclusion is that, as pointed out by Robertson, the
contribution of two-hole states is not negligible. But --in strong
contradistinction with the tacit conclusion of previous comparisons of theory
and observations-- we find a quite satisfactory agreement. A crucial point is
that, in the creation of secondary holes, electron shakeoff and not only
electron shakeup must be taken into account.
