Details on DARWIN and the search for extrasolar planets

The direct detection of an earth-like planet close to its parent star is challenging because the signal detected from the parent star is between 109 and 106 times brighter than the signal of a planet in the visual and infrared (IR), respectively. Future space based missions like DARWIN and TPF concentrate on the region between 6 pm and 18 mum, a region that contains the CO2, H2O, O-3 spectral features of the atmosphere. Using several small collecting telescopes and a beam combiner allows us to build an instrument with an angular resolution normally associated with monolithic telescopes of much larger diameters. The relative positions of the telescopes, forming the interferometer, are selected such that when the optical signals, collected by the individual telescopes, are coherently combined, the small angular distance between the planet and the star can be resolved. Different configurations of the free flying interferometer array influence the performance of the nulling array. The concepts for space nulling interferometers and the influence of different schemes of beam combination on the detected signal are investigated. The contribution of background noise to the detected signal is examined.