The ESA Cornerstone Mission GAIA, to be launched prior to 2012 and with
a nominal lifetime of 5 years, will improve the accuracy of Hipparcos
astrometry by more than two orders of magnitude.
GAIA high-precision global astrometric measurements will provide deep insights
on the science of extra-solar planets. The GAIA contribution is primarily
understood in terms of the number and spectral type of targets available
for investigation, and characteristics of the planets to be searched for.
Several hundreds of thousands of solar-type stars (F-G-K) within a sphere
of ~200 pc centered on our Sun will be observed. GAIA will be particularly
sensitive to giant planets (MP ~ MJ)
on wide orbits, up to periods twice as large as the mission duration, the
potential signposts of the existence of rocky planets in the Habitable Zone.
Thousands of new planets might be discovered, and a significant fraction
of those which will be detected will have orbital parameters measured to
better than 30% accuracy. By measuring to a few degrees
the relative inclinations of planets in multiple systems with favorable
configurations, GAIA will also make measurements of unique value towards a
better understanding of the formation and evolution processes of planetary