DARWIN NULLING INTERFEROMETER BREADBOARD Ⅱ: DESIGN AND MANUFACTURING

摘要

Nulling interferometry is a direct method to detect earth-like planets. To determine whether a planet is earth-like spectrometry can be performed which requires a broadband optical input signal from the planet. Nulling interferometry should decrease the broadband (λ≈ 6-18μm) star signal by about a factor of 10~6. For an ESA contract a nulling interferometer breadboard has been designed, manufactured and tested by TNO TPD together with and as subcontractor of Astrium GmbH in Germany. The set-up enables testing of two different phase shifter types (dispersive phase shifting and field reversal), two different star/planet simulator designs and consists of three sources, a star source, a planet source and a control source. The optical path difference is actively stabilized using an adaptive control scheme and a piezo activated cat's-eye delay-line. The bandwidth of one star source equals 1550 ± 15nm. First tests with this source at TNO TPD resulted in an optical path length stability of 0.5nm rms and a stable, repeatable nulling depth of 30000 (3.3·10~(-5)).