Preparatory studies for a mid-infrared nulling interferometry experiment at cryogenic conditions

Abstract

A space-based mid-infrared nulling interferometer is one of the most promising concepts to achieve one of the long-term goals of exoplanet science - the characterization of many terrestrial planets and the assessment of their potential habitability. In preparation of a potential future mission, we are continuing the efforts of previous mission concepts and their associated nulling testbeds that operated at ambient conditions. While they successfully proved that the required deep null can be achieved and stabilised over many hours, we are building a cryogenically cooled nulling interferometer testbed working in the potential mission wavelength range (4 - 18 μm) and with comparable sensitivity in order to demonstrate the measurement concept at fluxes similar to the astronomical targets. Many new challenges arise from this goal such as the need to optimize the setup for throughput and symmetry in order to avoid performance losses when exposed to unpolarized and broadband light. In this paper we present first concepts and theoretical results of a fully symmetric setup.