  The problem of how many trajectories of a random walker in a potential are
needed to reconstruct the values of this potential is studied. We show that
this problem can be solved by calculating the probability of survival of an
abstract random walker in a partially absorbing potential. The approach is
illustrated on the discrete Sinai (random force) model with a drift. We
determine the parameter (temperature, duration of each trajectory, ...) values
making reconstruction as fast as possible.
