排序方式: 共有49条查询结果,搜索用时 15 毫秒
41.
I. Kimura 《Space Science Reviews》1974,16(3):389-411
Observations and theoretical works so far made are reviewed in regard to the interrelation of VLF and ULF emissions. Quasi-periodic VLF emissions are one of the typical examples showing the interrelation between the two phenomena. The term modulation may be more appropriate to explain these phenomena. Tentative interpretations will be given of the VLF and ULF emissions which are closely associated through a modulation of the electron distributions. 相似文献
42.
In this paper, we consider a pointing control of a spacecraft using two single-gimbal control moment gyros (SGCMGs). Our pointing control problem is to make the line-of-sight of a camera or an antenna that is fixed on a body axis aim along a desired direction. To solve this problem, we first state the control objective for the pointing control through the angular momentum conservation principle. Then, we develop a gain-scheduled (GS) controller via linear parameter-varying (LPV) control theory. Finally, the feasibility of the proposed control method is shown by a numerical simulation. 相似文献
43.
Imawaki Shiro Uchida Hiroshi Ichikawa Kaoru Ambe Daisuke 《Space Science Reviews》2003,108(1-2):195-204
The mean sea-surface height obtained from satellite altimeters is different from the geoid by the amount of mean sea-surface
dynamic topography associated with ocean currents. Assuming geostrophy at the sea surface, the mean sea-surface dynamic topography
can be obtained from the mean sea-surface velocity field. This field is derived by combining anomalies (i.e., deviations from
the mean) of sea-surface velocity obtained from altimeter data and in situ surface velocities estimated from trajectories of surface drifting-buoys (hereafter, drifters). Where a drifter measured
the surface velocity, the temporal mean velocity can be estimated by subtracting the altimeter-derived velocity anomaly at
that time from the drifter-measured surface velocity. The method is applied to the surface flow field of the North Pacific,
using TOPEX/POSEIDON and ERS-1/2 altimeter data, and WOCE-TOGA surface drifter data obtained from October 1992 through December
2000. The temporal mean velocity field is estimated with a resolution of quarter degrees in both latitude and longitude. The
obtained mean velocity field clearly shows the Kuroshio and Kuroshio Extension, which are narrower and stronger than the climatological
mean features derived from historical hydrographic data averaged over several decades. Instantaneous velocities are estimated
by summing up these temporal mean velocities and anomalies, every ten days during the eight years. They compare well with
in situ velocities measured by the surface drifters. The instantaneous velocity field shows energetic fluctuation of the Kuroshio
Extension vividly.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
44.
Hajime Fukushima Kazunori Suzuki Liping Li Naoya Suzuki Hiroshi Murakami 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The tendency of over-estimation of sun-glint reflectance was found in GLI satellite ocean color data, after applying the traditional sun-glint model of Cox and Munk together with objective analysis wind data. ADEOS-II has provided a good opportunity to improve the glint model using data measured by GLI and SeaWinds, both onboard the satellite. With the help of simultaneous wind measurements achieved by SeaWinds, the Cox and Munk model is re-evaluated using GLI measurements to obtain a new relationship between the surface mean square slope and wind. The new model was found to be very close to the Cox and Munk under moderate wind speed but is much different under calm condition, where it shows similarity to the result reported by Ebuchi and Kizu. It also improves the ocean color data availability and the precision of sun-glint reflectance, based on the evaluation result of the generated Level 3 data products. 相似文献
45.
Yuichiro Ezoe Tomoki Kimura Satoshi Kasahara Atsushi Yamazaki Kazuhisa Mitsuda Masaki Fujimoto Yoshizumi Miyoshi Graziella Branduardi-Raymont Kumi Ishikawa Ikuyuki Mitsuishi Tomohiro Ogawa Takuya Kakiuchi Takaya Ohashi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
For the future Japanese exploration mission of the Jupiter’s magnetosphere (JMO: Jupiter Magnetospheric Orbiter), a unique instrument named JUXTA (Jupiter X-ray Telescope Array) is being developed. It aims at the first in-situ measurement of X-ray emission associated with Jupiter and its neighborhood. Recent observations with Earth-orbiting satellites have revealed various X-ray emission from the Jupiter system. X-ray sources include Jupiter’s aurorae, disk emission, inner radiation belts, the Galilean satellites and the Io plasma torus. X-ray imaging spectroscopy can be a new probe to reveal rotationally driven activities, particle acceleration and Jupiter–satellite binary system. JUXTA is composed of an ultra-light weight X-ray telescope based on micromachining technology and a radiation-hard semiconductor pixel detector. It covers 0.3–2 keV with the energy resolution of <100 eV at 0.6 keV. Because of proximity to Jupiter (∼30 Jovian radii at periapsis), the image resolution of <5 arcmin and the on-axis effective area of >3 cm2 at 0.6 keV allow extremely high photon statistics and high resolution observations. 相似文献
46.
Toyoshima M. Takayama Y. Takahashi T. Suzuki K. Kimura S. Takizawa K. Kuri T. Klaus W. Toyoda M. Kunimori H. Jono T. Arai K. 《Aerospace and Electronic Systems Magazine, IEEE》2008,23(8):10-18
Ground-to-satellite laser communication experiments between the optical ground station located in Koganei, central Tokyo, and a low earth orbit (LEO) satellite were jointly performed by the Japan Aerospace Exploration Agency and the National Institute of Information and Communications Technology. In 18 trials during three non-consecutive months, the satellite was acquired and tracked 61 % of the time, when clear or partly-clear conditions were predominant. The optical link was maintained for about 6 minutes when the satellite was visible in spite of the high angular velocity of the satellite. In 3 of the 18 trials, the link was not interrupted due to clouds during the six-minute transit. The failures (39% of the time) occurred when cloudy or rainy conditions were predominant. Fluctuation in the uplink received signal power was minimized by using multiple laser beam transmissions. The measured uplink and downlink bit error ratios were 10-7-10-4. These results demonstrate the applicability of free-space laser communication for not only geostationary earth orbit-LEO optical links but also ground-to-LEO optical links. 相似文献
47.
Satoru Katsuda Hiroshi Tsunemi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(3):383-389
We have observed the Cygnus Loop from the northeast (NE) to the southwest (SW) with XMM-Newton. We extracted spectra from 3′-spaced annular regions across the Loop and fitted them either with a one-kTe-component non-equilibrium ionization (NEI) model or with two-kTe-component NEI model. We found that the two-kTe-component model yields significantly better fits in almost all the spectra than the one-kTe-component model. Judging from the abundances, the high-kTe-component in the two-temperature model must be fossil ejecta while the low-kTe-component comes from the swept-up interstellar medium (ISM). The distributions of Ne, Mg, Si, and S for fossil ejecta appear to retain the onion-skin structure at the time of a supernova explosion, suggesting that significant overturning of the ejecta has not occurred yet. Comparing the relative abundances of fossil ejecta estimated for the entire Cygnus Loop with those from theoretical calculations for Type-II SN, the mass of the progenitor star is likely to be ∼13 M⊙. The trends of the radial profiles of kTe and emission integral for the swept-up ISM are adequately described by the Sedov model, suggesting that the swept-up ISM is concentrated in a shell-like structure. Comparing our data with the Sedov model, we found the ambient medium density to be ∼0.7 cm−3. Then, we estimated the total mass of the swept-up ISM and the age of the remnant to be ∼130 M⊙ and 13,000 years, respectively. Note that if the explosion occurred within a stellar wind cavity, then the density in the cavity, the total swept-up mass in the cavity, and the age of the remnant are estimated to be ∼0.14 cm−3, ∼25 M⊙, and ∼10,000 years, respectively. 相似文献
48.
In-flight Performance and Initial Results of Plasma Energy Angle and Composition Experiment (PACE) on SELENE (Kaguya) 总被引:1,自引:0,他引:1
Yoshifumi Saito Shoichiro Yokota Kazushi Asamura Takaaki Tanaka Masaki N. Nishino Tadateru Yamamoto Yuta Terakawa Masaki Fujimoto Hiroshi Hasegawa Hajime Hayakawa Masafumi Hirahara Masahiro Hoshino Shinobu Machida Toshifumi Mukai Tsugunobu Nagai Tsutomu Nagatsuma Tomoko Nakagawa Masato Nakamura Koh-ichiro Oyama Eiichi Sagawa Susumu Sasaki Kanako Seki Iku Shinohara Toshio Terasawa Hideo Tsunakawa Hidetoshi Shibuya Masaki Matsushima Hisayoshi Shimizu Futoshi Takahashi 《Space Science Reviews》2010,154(1-4):265-303
MAP-PACE (MAgnetic field and Plasma experiment—Plasma energy Angle and Composition Experiment) on SELENE (Kaguya) has completed its ~1.5-year observation of low-energy charged particles around the Moon. MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measured the distribution function of low-energy electrons in the energy range 6 eV–9 keV and 9 eV–16 keV, respectively. IMA and IEA measured the distribution function of low-energy ions in the energy ranges 7 eV/q–28 keV/q and 7 eV/q–29 keV/q. All the sensors performed quite well as expected from the laboratory experiment carried out before launch. Since each sensor has a hemispherical field of view, two electron sensors and two ion sensors installed on the spacecraft panels opposite each other could cover the full 3-dimensional phase space of low-energy electrons and ions. One of the ion sensors IMA is an energy mass spectrometer. IMA measured mass-specific ion energy spectra that have never before been obtained at a 100 km altitude polar orbit around the Moon. The newly observed data show characteristic ion populations around the Moon. Besides the solar wind, MAP-PACE-IMA found four clearly distinguishable ion populations on the dayside of the Moon: (1) Solar wind protons backscattered at the lunar surface, (2) Solar wind protons reflected by magnetic anomalies on the lunar surface, (3) Reflected/backscattered protons picked-up by the solar wind, and (4) Ions originating from the lunar surface/lunar exosphere. 相似文献
49.
An air-breathing pulse-laser powered orbital launcher has been proposed as an alternative to conventional chemical launch systems. The aim of the present study is to assess its feasibility through the estimation of its achievable payload mass per unit beam power and launch cost. A transfer trajectory from the ground to a geosynchronous Earth orbit (GEO) is proposed, and the launch trajectory to its geosynchronous transfer orbit (GTO) is computed using the realistic performance modeled in the pulsejet, ramjet, and rocket flight modes of the launcher. Results show that the launcher can transfer 0.084 kg of payload per 1 MW beam power to a geosynchronous earth orbit. The cost becomes a quarter of existing systems if one can divide a single launch into 24,000 multiple launches. 相似文献