Development of an optical diagnostic instrument for use in microgravity fluid physics research

An optical diagnostic instrument is being developed taking up design challenges derived both from experiment requirements for microgravity fluid physics research and from boundary conditions imposed by taking into account possible accommodation in a space laboratory. The instrument combines an observation system that provides an image of the fluid scene with a sharp focussed Schlieren overlay on a whole field basis, with an add-on facility to locate the observation window of various, exchangeable, narrow field diagnostic instruments at any desired position within the whole field of view. As a consequence, the instrument concept features diagnostic versatility with appreciable scope obtained within a rather compact lay-out. The instrument's capabilities and operational characteristics are investigated by means of an evolving breadboard set-up. Demonstration experiments are performed using real fluid systems (thermal plumes) as well as solid state reference measurement objects ("MP3"). The execution of exchangeable narrow field diagnosis is exemplified with a Michelson-type interferometer and a moire deflectometer. The future development of the instrument design concept, including the possibilities to expand its diagnostic scope and its data/image acquisition and processing capability, is presently under study.