  We present a detection criterion for exo-planets to be used with the space
mission COROT. This criterion is based on the transit method, which suggests
the observation of star dimming caused by partial occulations by planetary
companions. When at least three transits are observed, we show that a
cross-correlation technique can yield a detection threshold, thus enabling the
evaluation of the number of possible detections, assuming a model for the
stellar population in the Galaxy.
