排序方式: 共有7条查询结果,搜索用时 359 毫秒
1
1.
Masanori Homma Masayoshi Utajima Toshio Okamoto Kenji Hiraishi Susumu Takezawa 《Acta Astronautica》1983,10(3):125-131
This paper deals with a new concept, named “AMF Phasing”, which intends to minimize the effect of injection error that would result during apogee motor firing (AMF) of the spinning spacecraft. The characteristic of velocity increment error is derived analytically, based on the disturbed spinning motion during AMF. In order to precisely estimate the amount of fuel required for post-AMF orbital correction maneuvers, a probability model is proposed which estimates the total injection error probability combining the dominant error factors, i.e. pre-AMF attitude determination error and velocity increment error during AMF.It is shown that a substantial saving in fuel normally consumed for post-AMF can be expected, when the resultant velocity increment error contribution, which otherwise would be randomly directed in inertial space, is controlled so that it appears in the direction of local right ascension by igniting AKM at the proper instant (AMF Phasing). The procedure for AMF phasing, using a Sun pulse as a reference signal for the ignition timing is described in this paper. It was actually applied for GMS-2, Japan's second Geostationary Meteorological Satellite (HIMAWARI-II). The HIMAWARI-II post-AMF orbit determination shows that AMF Phasing worked successfully and it is concluded that a substantial fuel saving was achieved. 相似文献
2.
An experimental study was conducted to investigate the evolutions of unsteady vortex structures downstream a lobed mixer/nozzle.Anovel dual-plane stereoscopic PIVsystem was used to measure all 3-components of vorticity distributions to revealed both the large-scale streamwise vortices produced by the lobed mixer/nozzle and the Kelvin-Helmholtz vortex structures generated due to the Kelvin-Helmholtz instabilities simultaneously and quantitatively for the first time.The instantaneous and the ensemble-averaged vorticity distributions displayed quite different aspects about the evolutions of the unsteady vortex structures.While the ensemble-averaged vorticity distributions indicated the overall effect of the special geometry of the lobed nozzle/mixer on the enhanced mixing process,the instantaneous vorticity distributions elucidated many details about how the enhanced mixing process was conducted.In addition to quantitatively confirming conjectures of previous studies,further insight about the formation,evolution and interaction characteristics of the unsteady vortex structures downstream of the lobed mixer/nozzle were also uncovered quantitatively in the present study. 相似文献
3.
We review the evidence for electron acceleration in the heliosphere putting emphasis on the acceleration processes. There are essentially four classes of such processes: shock acceleration, reconnection, wave particle interaction, and direct acceleration by electric fields. We believe that only shock and electric field acceleration can in principle accelerate electrons to very high energies. The shocks known in the heliosphere are coronal shocks, traveling interplanetary shocks, CME shocks related to solar type II radio bursts, planetary bow shocks, and the termination shock of the heliosphere. Even in shocks the acceleration of electrons requires the action of wave particle resonances of which beam driven whistlers are the most probable. Other mechanisms of acceleration make use of current driven instabilities which lead to electron and ion hole formation. In reconnection acceleration is in the current sheet itself where the particles perform Speiser orbits. Otherwise, acceleration takes place in the slow shocks which are generated in the reconnection process and emanate from the diffusion region in the Petschek reconnection model and its variants. Electric field acceleration is found in the auroral zones of the planetary magnetospheres and may also exist on the sun and other stars including neutron stars. The electric potentials are caused by field aligned currents and are concentrated in narrow double layers which physically are phase space holes in the ion and electron distributions. Many of them add up to a large scale electric field in which the electrons may be impulsively accelerated to high energies and heated to large temperatures. 相似文献
4.
Application of time-variable process noise in terrestrial reference frames determined from VLBI data
Benedikt Soja Richard S. Gross Claudio Abbondanza Toshio M. Chin Michael B. Heflin Jay W. Parker Xiaoping Wu Kyriakos Balidakis Tobias Nilsson Susanne Glaser Maria Karbon Robert Heinkelmann Harald Schuh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(9):2418-2425
In recent years, Kalman filtering has emerged as a suitable technique to determine terrestrial reference frames (TRFs), a prime example being JTRF2014. The time series approach allows variations of station coordinates that are neither reduced by observational corrections nor considered in the functional model to be taken into account. These variations are primarily due to non-tidal geophysical loading effects that are not reduced according to the current IERS Conventions (2010). It is standard practice that the process noise models applied in Kalman filter TRF solutions are derived from time series of loading displacements and account for station dependent differences. So far, it has been assumed that the parameters of these process noise models are constant over time. However, due to the presence of seasonal and irregular variations, this assumption does not truly reflect reality. In this study, we derive a station coordinate process noise model allowing for such temporal variations. This process noise model and one that is a parameterized version of the former are applied in the computation of TRF solutions based on very long baseline interferometry data. In comparison with a solution based on a constant process noise model, we find that the station coordinates are affected at the millimeter level. 相似文献
5.
A review is given for cyclotron resonant interactions in space plasmas. After giving a simple formulation for the test particle approach, illustrative examples for resonant interactions are given. It is shown that for obliquely propagating whistler waves, not only fundamental cyclotron resonance, but also other resonances, such as transit-time resonance, anomalous cyclotron resonance, higher-harmonic cyclotron resonance, and even subharmonic resonance can come into play. A few recent topics of cyclotron resonant interactions, such as electron injection in shocks, cyclotron resonant heating of solar wind heavy ions, and relativistic modifications, are also reviewed. 相似文献
6.
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
7.
1