Astrometric methods and instrumentation to identify and characterize extrasolar planets: A review

I present a review of astrometric techniques and instrumentation used to search for, detect, and characterize extrasolar planets. First, I briefly summarize the properties of the current sample of extrasolar planets, in connection with predictions from theoretical models of planet formation and evolution. Next, the generic approach to planet detection with astrometry is described, with significant discussion of a variety of technical, statistical, and astrophysical issues to be faced by future ground-based and space-borne efforts in order to achieve the required degree of measurement precision. After a brief summary of past and present efforts to detect planets via milliarcsecond astrometry, I then discuss the planet-finding capabilities of future astrometric observatories aiming at microarcsecond precision. Finally, I outline a number of experiments that can be conducted by means of high-precision astrometry during the next decade, to illustrate its potential for important contributions to planetary science, compared to other indirect and direct methods for the detection and characterization of planetary systems.