INDIRECT PLANET DETECTION WITH GROUND-BASED LONG-BASE-LINE INTERFEROMETRY

Narrow-angle astrometry with long-baseline infrared interferometers can provide extremely high accuracies as required for indirect planet detection. Narrow-angle astrometric interferometry exploits the properties of atmospheric turbulence over fields smaller than the interferometer baseline divided by the atmospheric scale height. For such fields, accuracy is linear with star separation, and nearly inversely proportional to baseline length. To exploit these properties, the interferometer observes a relatively bright (< 13 mag(K)) target in the near infrared at 2.2 mum, and uses phase referencing to find a reference star within the 2.2-mum isoplanatic patch. With this technique faint references can be found for most targets. With baselines > 100 m, which also minimize photon-noise errors, and with careful control of systematic errors by using laser metrology, accuracies of tens of microarcseconds/square-root hour should be possible.