This paper presents an analysis and discussion of
the Nadir return in the context of radar timing. Results obtained
during the Commissioning Phase of TerraSAR-X in verification
and measurement of Nadir return and timing margins are
shown. Pre-launch assumptions about the Nadir margins were
verified and optimized, which led to an improvement in the
timing commanding, i.e. a relaxing of the timing. By means of
three early acquired TerraSAR-X images which contain Nadir
returns their characteristic properties are shown and explained
