It is commonly accepted that highly challenging planet finding missions such as Darwin and TPF need precursors on the
ground, for both technological demonstration and study of the exozodiacal clouds around potential targets. A first
instrument, GENIE, designed to be implemented in the interferometric laboratory of the VLTI, was studied by ESA and
scientific/industrial teams. In this paper we present a concept for ALADDIN, an operational nulling instrument to be
implemented at Dome C in Antarctica, and discuss the comparison with GENIE from the instrumental point of view.
Our preliminary design involves moderate ~1m size telescopes mounted on a 40m long rotating beam allowing
baselines up to 30m and feeding a 2-arm nulling beam combiner. When compared to GENIE, the rotating beam design
has the advantage of removing the need for both long-stroke delay line and dispersion control equipments. As a side
effect, the instrumental arrangement of ALADDIN finds itself more representative of what Darwin will be.
Furthermore, critical issues like phase control, photometric balance and instrumental background suppression are
expected to be relaxed by the improved atmospheric conditions, lower temperature, and simpler optical trains.
Calibration of geometrical stellar leakage will make advantage of the continuously adjustable baseline. As results, a
simpler instrument showing improved performance is expected. In conclusion, we see our ALADDIN concept as a
valuable alternative to GENIE, with a quite stronger scientific potential and a considerably simplified instrumental