Fluid physics instrumentation study. Part 2: Design report

A proposed optical diagnostics instrument (PODI) for fluid physics studies in microgravity is described. Components to be used in a breadboard system for PODI are identified and performance predictions for this system are assessed. Photography (and photogrammetry) are used for the definition of positions (P) within the field of view as related to the determination of locations, shapes, etc., of free liquid surfaces, bubbles, etc. Photography is executed in a diffusely illuminated environment, provided by a white light source and diffuser. Refractive index gradients are studied by observing the deflection of light beams participating in the imaging processes (object grating G1 on reference grating G2 and P on P') in a sharp focused Schlieren system. Grating G1 is diffusely back-illuminated by a white light source. Quantitative local diagnosis is achieved by determining optical path lengths by a system fitted with a Michelson interferometer. The system can be moved over the field of view of the main (wide field) optical system. It employs a laser light source and is provided with suitable relay optics in order to record the interferometric information by means of the (wide field) camera.