The Protein Crystallisation Diagnostic Facility (PCDF) is a multi-user facility to study the protein crystallisation under the conditions of micro-gravity onboard the International Space Station (ISS) Columbus facility. Large size protein crystals will growth under reduced gravity in thermally controlled reactors. A combination of diagnostic tools like video system, microscope, interferometer, and light scattering device shall help to understand the growth phenomena.
The Fluid Science Laboratory (FSL) is a multiuser facility developed and built by the European Space Agency (ESA). Its launch onboard the Columbus Laboratory, a module of the International Space Station (ISS) is foreseen in June 2005 according to the present planning. FSL can host sequentially Experiment Containers dedicated to a specific experiment in various scientific areas like fluid science, crystal growth, foams and directional solidification within transparent media and, owing to its adaptable diagnostic tools and its modularity on several levels, complementary science areas such as colloid and aerosol physics, particle agglomeration and plasma crystals are envisaged. The visualisation, monitoring and control of the experiment is based on a set of optical diagnostics included in the FSL facility such as visualisation in two perpendicular directions, velocimetry, ESPI and Wollaston interferometry, Schlieren working in transmission and reflection modes, infrared and a high speed camera. The paper will describe the optical tools included in FSL and their performances.
Several applications require the identification of chemical elements during re-entry of material in the atmosphere. The materials can be from human origin or meteorites. The Automated Transfer Vehicle (ATV) re-entry has been filmed with conventional camera from airborne manual operation. In order to permit the identification of the separate elements from their glow, spectral analysis needs to be added to the video data. In a LET-SME contract with ESA, Lambda-X has built a Fourier Transform Imaging Spectrometer to permit, in a future work, to bring the technology to the readiness level required for the application. In this paper, the principles of the Fourier Transform Imaging spectroscopy are recalled, the different interferometers suitable for supporting the technique are reviewed and the selection process is explained. The final selection of the interferometer corresponds to a birefringent prism based common path shear interferometer. The design of the breadboard and its performances are presented in terms of spatial resolution, aperture, and spectral resolution. A discussion is open regarding perspective of the technique for other remote sensing applications compared to more usual push broom configurations.
We present a new optical tomography technique based on phase-shifting schlieren deflectometry. The principle is that of
computerized tomography. The three-dimensional profile is reconstructed from the deflection angles of rays passing
through the tested object. We have investigated optical phantoms chosen in view of the characterization of dendritic
growth in a solidification process. Promising results have been obtained with a homogeneous sphere and a bundle of
200μm fibers. The deviation angles exceed two degrees with a variation of the refractive index ▵n=0.025.
In the frame of science in microgravity, the investigation of dendritic growth in a solidification process has been chosen as a test case in order to determine the ultimate performance and the limits of interferometric optical tomography, a well dedicated optical diagnostic tool for transparent media. In the frame of 3D-shape measurements on the morphology of transparent succinonitril directional solidification front, the relatively slow temporal evolution of the solidification front allow to record tomographic projections during 30 seconds without having modifications. This would lead to the possibility to use a rotating device holding the sample in order to record sequentially the different views or set of views of the tomograph. Interferometry through its high sensitivity to refractive index variation is able to discriminate between solid phase and its surrounding solution. Due to a high number of parameters involved in tomographic measurements and reconstruction, it was necessary to analyze step by step their influences.
Representative static model scenes have been manufactured and in depth independently characterized by X-ray microtomography in air. The same model scenes have been inserted into a single arm phase-shift Mach-Zehnder interferometer again by rotating object in order to acquire up to 256 projections. Finally a tomographic reconstruction process has been performed, the results of which were compared to the reconstructions gained from the micro x-ray measurements. This work shows the potential of interferometric optical tomography as well as its limits.
Interferometry has always been a powerful tool to diagnose the response of liquids, when changes of status parameters induce modifications in their optical properties. Interferometric measurements are based on the ability to measure variations, around a reference configuration, in the optical path length or the refractive index. Investigations done so far on heat convection driven by capillary forces, indicate that the observation of both the bulk phase and of the free surface, is instrumental for the understanding of the physical mechanisms steering the heat transfer phenomena in 'weightless liquids'. When used in space application, conventional interferometers suffer of some fundamental drawbacks, because of the severe requirements in terms of mechanical stability of the optical elements. Holographic interferometry removes the most stringent limitations of classical interferometry, but requires precise positioning of the recording plate, with accuracy better than half a wavelength. The superior feature of an electronic speckle pattern interferometer (ESPI) is that it enables real time correlation fringes to be recorded by a video camera and displayed on a television monitor, without recourse to any form of photographic processing or plate relocation. This comparative ease of operation allows the technique of ESPI to be extended to considerably more complex problems of deformation analysis and measurement of refractive index modulation. Since it basically works as a time differential interferometer, measurements can always be referred to a well known configuration and condition of the test sample, reducing or even eliminating the requirements on mechanical stability. This paper describes how double-path ESPI are accommodated within the optical diagnostics of a microgravity payload, fluid physics facility, due to launch in 1998 on the Russian retrievable capsule FOTON. The two- ESPI layout permits one to observe and quantify the deformation of the free surface of a liquid subjected to a thermal gradient.Motions induced by the convective flows in the bulk phase can be monitored at the same time. The main features of the ESPI are presented together with design outlines and optical performances.