EDITORIAL

Abstract

Under microgravity conditions, various physical phenomena are significantly altered, in particular convection, buoyancy, hydrostatic pressure and sedimentation. This affects scientific disciplines such as fluid physics and transport phenomena, combustion, crystal growth and solidification, biological processes and biotechnology. Microgravity is instrumental in unmasking processes that are overshadowed in normal gravity. Microgravity may therefore be regarded as an important tool for increasing precision in the measurement of thermophysical properties, for improving models of complex phenomena, and hence refining manufacturing processes on Earth. Microgravity or near-weightlessness corresponds to a free-fall situation, and can be achieved by various means and for different durations: drop towers and drop shafts (up to 10 seconds), aircraft flying parabolic trajectories (about 20 seconds), sounding rockets (up to 15 minutes), unmanned satellites (weeks or months) and manned orbiting systems such as the Shuttle (a few weeks), Mir and finally the International Space Station, which will be in operation for a decade at least. This special issue brings together new instrumentation and diagnostics techniques in microgravity research for future scientific utilization in the International Space Station (ISS). The ISS is a cooperative venture by five international partners - the USA, Russia, Europe, Canada and Japan - and has been conceived as a multipurpose, manned infrastructural element in the lower Earth orbit for scientific and technological research under microgravity conditions. Microgravity research covers a wide range of activities from fundamental physics, solidification physics, physical chemistry and fluid science, to biology, biotechnology, human physiology and medicine. Measurement Science and Technology, with its strong publishing history in optical measurement technology, has devoted this feature issue to recent developments in the field of microgravity instrumentation. The aim of the feature is to provide the reader with a comprehensive overview of the current state-of-the-art and possible future developments in instrumentation and diagnostics for experiments in space. The issue comprises 17 contributed papers on various aspects of the field. Topics covering diverse instrumentation and diagnostics in the field of fluid physics and combustion sciences under microgravity conditions such as digital holography, miniaturized laser Doppler velocimetry, laser-induced fluorescence techniques, 3D photogrammetric methods, optical tomography and different interferometric instrumentation are appropriate. There are also a number of contributions from research groups covering several topics relating to a particular application. As guest editor, I would like to thank all the contributing authors, the referees and the Institute of Physics Publishing team for making this such a successful special issue. Christoph Egbers, Bremen Guest Editor August 1999