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Development and application of holographic particle image velocimetry techniques for microgravity applications

Holographic particle image velocimetry instruments at both velocity extremes have been developed and applied. Except for the type of laser required, the fundamental recording and data processing methods are similar for both cases. This paper summarizes recording and reconstruction schemes, software for data reduction, and methods for data presentation. An example application focuses on the extreme low-velocity case in which a three-size matrix of tracer particles was added to a solution in a crystal-growth-in-space experiment to quantify and analyse microconvection in a microgravity environment. Over 1000 holograms of 1000 particles were produced in a Spacelab mission, leading to the need to process millions of images. Particle velocities ranged from 0.1 to . Reconstructed particle images were located with a computer traversed microscope imaged on a CCD array, and tracked with software designed to establish a reference frame in each hologram and precisely locate the particle centres. The measurements allow determination of the convective field, the residual gravitational field and gravity-jitter.