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Manabe T.,Osaka Prefecture University | Nishibori T.,Japan Aerospace Exploration Agency | Mizukoshi K.,Advanced Engineering Services Co. | Otsubo F.,Advanced Engineering Services Co. | And 3 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2012

This communication describes the results of the measurements made for the flight model of the offset Cassegrain antenna of superconducting submillimeter-wave limb-emission sounder (SMILES) aboard the International Space Station. We have employed a near-field phase retrieval method in which the aperture phase distribution is estimated only from the amplitude distribution measurements over two near-field planes. The far-field patterns estimated from the estimated near-field patterns were compared with theoretical calculations based on physical optics in which the surface errors measured for the main and sub reflectors were taken into account. As a result of the comparison, the far-field patterns estimated from the phase retrieval method were found to be in very good agreement with the physical-optics calculations to the sidelobe levels as low as 55 dB. We have also found that patterns of machined flaws on the surface of the main reflector were clearly identified in the retrieved near-field phase pattern. This demonstrates that the phase retrieval is an effective method to evaluate aperture antennas in the submillimeter-wave region, where accurate phase measurement is rather difficult. © 1963-2012 IEEE.

Ishikawa T.,Japan Aerospace Exploration Agency | Paradis P.-F.,Japan Aerospace Exploration Agency | Okada J.T.,Japan Aerospace Exploration Agency | Kumar M.V.,Japan Aerospace Exploration Agency | Watanabe Y.,Advanced Engineering Services Co.
Journal of Chemical Thermodynamics | Year: 2013

Viscosities of tungsten, rhenium, osmium, tantalum, and molybdenum have been measured by the oscillation drop method with an improved procedure. The measured data exhibit less-scatter than our previous measurements. Viscosity at the melting temperature of the investigated metals showed a good agreement with literature values and some predicted values. © 2013 Elsevier Ltd. All rights reserved.

Ishikawa T.,Japan Aerospace Exploration Agency | Ito Y.,Shibaura Institute of Technology | Okada J.T.,Japan Aerospace Exploration Agency | Paradis P.-F.,Japan Aerospace Exploration Agency | And 2 more authors.
Measurement Science and Technology | Year: 2012

A spectral emissivity measurement system combined with an electrostatic levitator was developed for high-temperature melts. The radiation intensity from a high-temperature sample was measured with a multichannel photospectrometer (MCPD) over the 700-1000 nm spectral range, while a Fourier transform infrared spectrometer (FTIR) measured the radiation over the 1.1-6 m interval. These spectrometers were calibrated with a blackbody radiation furnace, and the spectral hemispherical emissivity was calculated. The system's capability was evaluated with molten zirconium samples. The spectral hemispherical emissivity of molten zirconium showed a negative wavelength dependence and an almost constant variation over the 1850-2210 K temperature range. The total hemispherical emissivity of zirconium calculated by integrating the spectral hemispherical emissivity was found to be around 0.32, which showed good agreement with the literature values. The constant pressure heat capacity of molten zirconium at melting temperature was calculated to be 40.9 J mol -1 K-1. © 2012 IOP Publishing Ltd.

Suzuki S.,Advanced Engineering Services Co.
Nihon Kikai Gakkai Ronbunshu, C Hen/Transactions of the Japan Society of Mechanical Engineers, Part C | Year: 2013

Generally, many space satellites have large solar array panels for power generation and large antennas for observation and communication. The panels and antennas must be lightweight because of the payload weight limit of the launch vehicle. So, they are very flexible, with little damping ability. This results in vibrations cause serious problems. When the thermal environment around a flexible structure on orbit such as a solar array panel changes to cold or hot, the flexible structure produces its own deformation or vibration. These occur most often during rapid temperature changes called thermal snap or thermally-induced vibration, which has been known to cause attitude disturbance in Low Earth Orbit (LEO) satellites. Thermal snap vibration occurring on a flexible solar array panel is very slow. It is very difficult to measure thermal snap motion by sensors such as accelerometer. The behavior of a space structure affected by thermal snap has never been observed directly in space so far. This report presents the measurement results of "IBUKI" solar array panel's behavior using monitor camera. © 2013 The Japan Society of Mechanical Engineers.

Adachi S.,Japan Aerospace Exploration Agency | Kinoshita K.,Japan Aerospace Exploration Agency | Takayanagi M.,Japan Aerospace Exploration Agency | Miyata H.,Advanced Engineering Services Co.
Journal of Crystal Growth | Year: 2011

In order to investigate more suitable sample configurations for obtaining radially larger and more homogeneous compound semiconductor crystals, a two-dimensional model of the traveling liquidus-zone method is introduced. From numerical results of the model, it is found that inhomogeneity increases with the thermal conductivity of a crucible wall. This is mainly attributed to the heat flow slanted towards the crucible wall near an interface. The numerical results show, however, that the low thermal conductivity of the crucible does not sufficiently reduce the inhomogeneity, which is caused by the slanted heat flow. We also investigate the influence of a seed crystal. It is found that a seed crystal with large thermal conductivity is far more effective to improve the homogeneity. © 2011 Elsevier B.V. All rights reserved.

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