Optimized setup for active compensation of distortions for interferometric techniques onboard the International Space Station

摘要

The main part of the Fluid Science Laboratory (FSL) that is under development for the Columbus Orbital Facility is the Optical Diagnosis Module (ODM). It provides quantitative measurements of fluid science experiments with the help of different interferometric techniques. The assembly of these methods is based on a Mach-Zehnder-Interferometer. Because of the employment on the FSL the design of this interferometer has several requirements regarding volume, mass, modularity, operational needs and especially an environment with thermal and mechanical distortions of the interferometer. At BIAS an interferometer was designed that detects the misalignment due to external distortions and compensates it. The design is based on a simplified Hartmann-Sensor and detects wavefront tilt and curvature errors. The active compensation of these errors is realized by piezoelectric driven optical components and operates in realtime but cannot compensate the curvature errors completely. In this paper we describe the construction of a modified setup that compensates wavefront tilt and curvature errors in a temperature range from 15?C to 35?C sufficiently for the planned applications. The new design is substantial simpler and hence the passive stability is better as well. The results of thermal tests with the new setup are demonstrated and show the enhanced stability of the new actively stabilized interferometer.