M. G. Lattanzi, A. Spagna, A. Sozzetti
Osservatorio Astronomico di Torino, Italy
Stefano Casertano
Space Telescope Science Institute, Baltimore MD
Space-based astrometric missions, such as Hipparcos and the proposed GAIA and SIM missions, can yield frequently sampled, accurate position measurements for a large number of stars with uniform accuracy. Using Monte Carlo simulations, we assess the probability of identifying planets around nearby stars in such databases. The simulations are realistic and include effects such as a non-circular, randomly oriented planetary orbits, parallax and proper motion for the parent star, a Hipparcos-like scanning law and a finite mission length. The probability of false detections is also assessed. We give a simple parametrization of the discovery probability, based on the ratio of the astrometric signature to the accuracy of individual astrometric measurements.