  We consider the problem of estimating a vector of unknown constant parameters
for a class of hybrid dynamical systems -- that is, systems whose state
variables exhibit both continuous (flow) and discrete (jump) evolution. Using a
hybrid systems framework, we propose a hybrid estimation algorithm that can
operate during both flows and jumps that, under a notion of hybrid persistence
of excitation, guarantees convergence of the parameter estimate to the true
value. Furthermore, we show that the parameter estimate is input-to-state
stable with respect to a class of hybrid disturbances. Simulation results
including a spacecraft application show the merits of our proposed approach.
