Single and double Bracewell nulling interferometer in space

As part of a NASA NRA study we have examined the design and use of a small Bracewell nulling interferometer in space for observations of Jovian and terrestrial planets in the 4-12 μm spectral region. At these wavelengths, the contrast is typically 10^-7 for most planets while younger and/or more massive Jovian planets have a contrast 100 times better. For planets farther from their star than Earth, a short baseline can provide good null depth and still have adequate resolution. With the single Bracewell nulling interferometer described here, massive/young giant planets far from their star are not difficult to observe and young Jovian mass planetary systems as far as 100 pc can be probed. A program to study planetary systems like the solar system is much harder. In the case of older and smaller planets, distinguishing the planet signal from the star and local zodiacal background is much harder and requires both high stability of the gain for the IR detectors, and nulling over periods of hours. The difficulties of a 2-telescope, single Bracewell nuller are overcome using a dual Bracewell nuller consisting of four telescopes, and phase chopping between two null beams. Double Bracewell nulling described here will have the potential to detect Earth's around 20 nearby stars.