  The H.E.S.S. experiment in Namibia, Africa, is designed to study the origin
of high energy cosmic rays from 100 Gev to few tens of TeV, using the Cherenkov
technique. To minimize the systematic errors on the derived fluxes of the
measured sources, one has to calculate the impact of the atmospheric
properties, namely the extinction parameter a. A LIDAR can provide this kind of
information within the detectable energy range of the experiment. In this paper
we report on the hardware components, operation and data taking of such a
system installed on the HESS site for the last three years.
