Detection and Characterization of Extra‐Solar Planets: Future Space Missions Available to Purchase

Various techniques are being used to search for extra‐solar planetary signatures, including accurate measurement of positional (astrometric) displacements, gravitational microlensing, and photometric transits. Planned space experiments promise a huge increase in the detections and statistical knowledge arising from transit and astrometric measurements. In contrast, imaging of even nearby Earth‐mass planets in the habitable zone and the measurement of their spectral characteristics, typified by the TPF and Darwin missions, represents an enormous challenge. A number of proposed precursors aimed at exploiting coronagraphy or occultations are being studied. Beyond TPF/Darwin, Life Finder would aim to produce confirmatory evidence of the presence of life, while an Earth ‘imager’, some massive interferometric array providing resolved images of a distant Earth, appears only as a distant vision. A 10 nas astrometric mission would detect ‘Earths’ systematically out to 100 pc.