Planet Discoverer Interferometer I: PDI, a potential precursor to Terrestrial Planet Finder

We consider a possible precursor interferometer to Terrestrial Planet Finder. The precursor called Planet Discoverer Interferometer (PDI) would search for broadband 10 μm radiation from possible terrestrial planets orbiting stars out to a distance of 8-10pc and at an angular separation of at least 0.1 arcseconds. There are about 20 stars of types A,F,G and K around which an Earth-analog might be detected. PDI would be able to confirm such planets by seeing their orbital motion. PDI would also be able to observe 5 μm radiation from the more massive and younger gas-giant planets around stars up to distances ∼ 150 pc, separated from their star by more than 0.05 arc seconds. It would also see the re-radiated thermal radiation of Jupiter-like planets at temperatures above ∼130K. The device would be a 15m long truss with four SIRTF-like telescopes. It would need to be in a SIRTF-like Earth-trailing orbit, and would be radiatively cooled. A very preliminary design suggest that PDI could fit into the shroud of a Delta II rocket. Similar preliminary calculations suggest that the total lifetime cost of such a mission would be under $300M. Detailed studies of this concept are in process.