Showing papers by "Japan Aerospace Exploration Agency published in 1998"

Formation mechanism of Japan Sea Proper Water in the flux center off Vladivostok

Abstract: It is known that wintertime air-sea interaction in the Japan Sea, enhanced by outbreaks of dry and cold air masses from the Eurasian continent, generates a characteristic water mass called Japan Sea Proper Water (JSPW) through deep convection. Using NASA scatterometer (NSCAT) wind vectors with high spatial resolution of 25 km, the role of the wind field over the Japan Sea in JSPW formation was investigated during the period of winter monsoon. It is revealed by NSCAT observations that the wintertime surface winds over the Japan Sea are strongly influenced by the upstream topography of the coastal region of the Eurasian continent. A strong wind area appears off Vladivostok, both in the snapshot and the monthly mean wind fields. The dynamics behind this strong wind flow may be attributed to the highly stratified surface wind being blocked by the coastal mountains and exiting through the narrow valley near Vladivostok into the Japan Sea. The NSCAT winds are coupled with European Centre for Medium-Range Weather Forecasts air temperature and humidity and Japan Meteorological Agency sea surface temperature (SST) data for turbulent flux estimation. Monthly mean wind speed, momentum flux, sensible heat flux, latent heat flux, and evaporation have peak values exceeding 9 m s -1 , 0.275 N m -2 , 170 W m -2 , 130 W m -2 , and 120 mm, respectively, in the strong wind area, which has a diameter of about 150 km. Multichannel sea surface temperature (MCSST) images of the Japan Sea for late January 1997 show that the cold SST (∼0°C) area extends from the coastal region to the outer sea off Vladivostok. The MCSSTs decreased by 1°C for January in this region. The cold SST region coincides with the strong wind area, and both locations agree well with the JSPW formation region, which, according to Sudo [1986], is north of 41°N between 132° and 134°E. The spatial agreement strongly suggests that the wind, enhanced by the topographic effect around Vladivostok, causes the large turbulent heat flux and evaporation in this area, which generates the coldest SST and dense water mass, i.e., JSPW. This may be a process of coastal topography-air-sea interaction that leads to deep-sea water formation in the Japan Sea. Because of the concentrated feature of turbulent fluxes and the inferred relation to the center of deep convection phenomenon, the strong wind area is called the flux center in this study.

Inverse Design Method for Wings of Supersonic Transport

Abstract: A practical inverse design method for supersonic airfoils/wings has been developed. The method is based on Takanashi's iterative "residual-correction" concept. A geometry that materializes a specified pressure distribution is sought by solving an integrodifferential form of the linearized small perturbation (LSP) equation. The integration is limited to the Mach forecone from the point of interest. Several design results are presented Nomenclature

Electronic system for the Astro-E Hard X-ray Detector

Abstract: The Hard x-ray Detector (HXD) is one of three instruments on the fifth Japanese x-ray astronomy satellite, Astro-E, scheduled for launch in 2000. The sensitivity of the Astro-E HXD will be higher by more than one order of magnitude than that of nay previous instrument between 10 keV and several 100 keV. The electronic system is designed to handle many independent data channels from the HXD within the limitation of size and power consumption required in Astro-E. In this paper, we will present the design and the preliminary performance of the processing electronic system.

Novel Oxygen Sensor Based on Quenching of Triplet-Triplet Absorption of Zinc Tetraphenylporphyrin

Abstract: A novel oxygen sensor based on the quenching of triplet-triplet absorption of zinc tetraphenylporphyrin (ZnTPP) molecules by oxygen has been developed. The excited triplet lifetime of ZnTPP-PS film...

Relation between injection conditions and flowfield in scramjet combusters

Abstract: The pre-ignition phase flow-field in a supersonic combustor with perpendicular injectors behind a backward-facing step was simulated with cold airflow and inert gas injection. The effects of injector configuration on pressure and injectant concentration in the recirculation region between the step and the injectors were investigated. The diameter and spacing of injectors were changed, while distance between the step and the injectors was fixed. The pressure in the recirculation region was found to be almost uniform and its values with different configurations were well correlated with the momentum ratio of the injectant to the mainstream. This ratio took the dynamic pressure ratio, the diameter, and the spacing into account. However, the injectant concentration in the recirculation region was not as uniform as the pressure, and did not show a correlation with the momentum ratio. Nomenclature d = injector orifice diameter h = height of backward-facing step, 6 mm p static pressure pb = step-base pressure Pc = mainstream pressure at stagnant condition ps mainstream static pressure upstream of step Rm = momentum ratio of the injectant to mainstream Rq = dynamic pressure ratio of the injectant to mainstream 5 = injector spacing T= temperature 7= injectant volume concentration x = streamwise distance from step y = spanwise distance from combustor centerline 9 = momentum thickness of boundary layer Copyright © 1998 by the American Institute of Aeronautics and Astronautics, Inc. All right reserved. * Graduate Student, Department of Aeronautics and Space Engineering. t Professor, Department of Aeronautics and Space Engineering, Member AIAA. ± Researcher, Ramjet Combustion Laboratory, Ramjet Propulsion Research Division, Member AIAA. § Senior Researcher, Ramjet Combustion Laboratory, Ramjet Propulsion Research Division. Subscripts R recovery w = wall

Performance of a digital video camcorder for the Autonomous Biological System experiment onboard Space Station Mir.

Abstract: A video imaging and recording system was utilized in the Autonomous Biological System experiment onboard the space station Mir. Video image of the mini-ecological system was successfully recorded. The whole system was retrieved to the ground after its operation in orbit for four months. Performance of the video system is summarized here together with technical problems encountered. Defects of pixel had been developed in the imaging device. Cause of these defects could be attributed to its exposure against space radiation. Auto white balance was another function of the camcorder that was deviated from normal range of its performance once in orbit but recovered to normal after a while. Possible use of imaging devices for dosimetry is proposed to record space radiation environment at the site close to the experiment.

Longitudinal flight control for space vehicle's automatic landing

Abstract: This paper discusses a longitudinal flight path control designed and flight tested for Automatic Landing Flight Experiment, ALFLEX. ALFLEX, the flight test of which was conducted in 1996, demonstrated Japanese potentials for developing a reentry space vehicle's automatic landing technology. In the program, however, longitudinal flight path control after the preflare maneuver is one of the critical items needed to satisfy the design requirement for landing on a limited length runway. Robustness against uncertainties and sensor errors is a key issue in longitudinal flight path control. The design was carefully conducted and flight tested. Although the flight test proved that the design result satisfied all the landing requirements, it identified critical parameters affecting the landing performance, such as longitudinal aerodynamics, navigation error and air data sensor error. This paper describes data obtained through the development and flight test, as well as further investigation conducted after the flight test in order to improve landing performance for the future space vehicle development. In the design review, a new approach called stochastic gain tuning is adopted, where the guidance feedback gain is tuned to maximize the probability of mission achievement. The results indicate some possibility of robustness improvement.

Scene feature matching analysis of JERS-1 SAR images

Abstract: A method to examine the shifts in individual surface features in multi-temporal SAR images has been proposed. First, line-like and boundary-like features were extracted from SAR imagery using the pixel swapping method. The extracted feature images were then tied to observe an overall shift in individual features. The authors applied this method to two JERS-1 SAR images of the same path-row observed on different dates. They observed that the shift in flat areas was simple, but that in mountainous regions, there was a clear difference in the direction of the shift in ridges and valleys caused by the slightly different orbital characteristics of the satellite between the two images. In addition, care in choosing appropriate tie points was found to be important. The method used in this investigation is expected to be useful in planning an appropriate strategy for the coregistration of images, such as in SAR images used for change detection in environmental monitoring, and InSAR.

Two boosted black holes in asymptotically de Sitter space-time: Relation between mass and apparent horizon formation

Abstract: We study the apparent horizon for two boosted black holes in the asymptotically de Sitter space-time by solving the initial data on a space with punctures. We show that the apparent horizon enclosing both black holes is not formed if the conserved mass of the system (Abbott-Deser mass) is larger than a critical mass. The black hole with too large AD mass therefore cannot be formed in the asymptotically de Sitter space-time even though each black hole has any inward momentum. We also discuss the dynamical meaning of AD mass by examining the electric part of the Weyl tensor (the tidal force) for various initial data.

Calibration and validation of the ocean color information from ADEOS OCTS

Abstract: This paper presents the calibration and validation results of the OCTS's ocean color information, e.g., the chlorophyll-a (Chl-a), and the normalized water leaving radiance (nlw). First, OCTS was calibrated for interdetector sensitivity, dark current variability, and absolute gain using internal and external calibration sources. Second, OCTS ocean color information was validated using in-situ measurements for Chl-a and nlw. The atmospheric correction algorithm was tuned using 17 in-situ Chl-a and 11 in-situ nlw measurements, which were observed simultaneously with OCTS under cloud-free conditions. It was then confirmed that OCTS Chl-a has an accuracy of 68%. Furthermore, it was also confirmed that geometric accuracy is 1.3 km and stripes are reduced significantly.