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Noriyuki Namiki Takahiro Iwata Nobuyuki Kawano Fumio Fuke Naoki Tateno Kazuyoshi Asari Hirotomo Noda Yusuke Kono Hideo Hanada Yukihiro Yahagi Zen’ichi Yamamoto Koji Tanaka Mitsuo Yamada Koji Matsumoto Sander Goossens 《Space Science Reviews》2010,154(1-4):103-121
The Japanese lunar mission Selenological and Engineering Explorer (SELENE) was launched in September 2007 and continued its mission until June 2009, when the main orbiter impacted with the surface of the Moon. SELENE consisted of three satellites: Main, Rstar, and Vstar. Rstar’s tasks were to forward up-link signals from the Usuada Deep Space Center (UDSC) to Main, and to down-link returning signals from Main to UDSC. We refer to this tracking sub-system as a four-way Doppler measurement. In contrast, conventional tracking systems between Rstar and UDSC as well as between Main and ground stations are referred to as two-way Doppler and range measurements. Using Main and Rstar, we successfully observed the gravity field over the farside of the Moon. Because four-way Doppler measurements via a relay sub-satellite were a fundamental experiment in space for Japanese space agencies, compatibility of radiometric instruments onboard Main and Rstar to UDSC were carefully examined at the UDSC using components manufactured for flight models. These tests not only proved the feasibility of the four-way Doppler measurements but also provided biases and variations of the four-way Doppler and two-way Doppler and range measurements that were later taken into account during the processing of tracking data and the analysis of the lunar global gravity field. 相似文献
2.
Numerical simulation of the terrestrial ring current is reviewed. After mentioning ‘modules’ which are needed to be taken
into consideration in a ring current simulation, we discuss growth and decay of the ring current. At least four different
paradigms have been proposed to account for the ring current development in the past forty years, i.e., the convection paradigm, the substorm paradigm, the diffusion paradigm, and the ionosphere paradigm. As for the proton ring
current, a simulation under the convection paradigm gives reasonable results which are in fair agreement with observations
with respect to the Dst variation as well as the radial and longitudinal energy density variation of protons when the convection
electric field depending on solar wind parameters is given. The proton energy density is observed to be enhanced (weakened)
on the nightside, and be weakened (enhanced) near noon during a storm main phase (recovery phase). This characteristic is
probably understood to mean that a large-scale and long-standing electric field dominates other electric fields during the
storm main phase, e.g., a locally induced electric field (the substorm paradigm) and a highly fluctuated electric field (the diffusion paradigm).
The declining of the ring current is shown to be triggered by the decrease in the convection electric field at the beginning
of a storm recovery phase, but the decrease in the convection electric field hardly contributes the decay of the ring current.
The charge exchange or other loss processes is needed for the substantial decay of it. An ultimate decay rate (several hours)
is achieved when the strong diffusion takes place, or when the plasma sheet density drastically decreases while the charge
exchange is estimated to provide rather slow decay (a half of day). Diagnosis tools for investigating the ring current, which
are expected to bring us a new insight, are proposed in the latter section.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
Xiaopeng XUE Yusuke NISHIYAMA Yoshiaki NAKAMURA Koichi MORI Yunpeng WANG ChihYung WEN 《中国航空学报》2018,31(1):54-64
This paper presents a detailed investigation of unsteady supersonic flows around a typical two-body configuration, which consists of a capsule and a canopy. The cases with different trailing distances between the capsule and canopy are simulated. The objective of this study is to examine the detailed effects of trailing distance on the flow fields and analyze the flow physics of the different flow modes around the parachute-like two-body model. The computational results show unsteady pulsating flow fields in the small trailing distance cases and are in reasonable agreement with the experimental data. As the trailing distance increases, this unsteady flow mode takes different forms along with the wake/shock and shock/shock interactions, and then gradually fades away and transits to oscillate mode, which is very different from the former. As the trailing distance keeps increasing, only the capsule wake/canopy shock interaction is present in the flow field around the two-body model, which reveals that the unsteady capsule shock/canopy shock interaction is a key mechanism for the pulsation mode. 相似文献
4.
Hideo HANADA Seiitsu TSURUTA Kazuyoshi ASARI Hiroshi ARAKI Hirotomo NODA Shingo KASHIMA Ken-ichi FUNAZAKI Fuyuhiko KIKUCHI Koji MATSUMOTO Yusuke KONO Hiroo KUNIMORI Sho SASAKI 《深空探测学报》2014,1(3):200-204
使用面包板模型和仿真方法,在实验室内研究月球指向就位测量望远镜(ILOM)的基本特征,如望远镜星像中心点位置精度、温度效应、倾斜以及地面震动的影响。使用这个技术预期在月球表面观测月球自转时可以达到1ms的精度。将在地面上开展测试验证观测以全面评价达到优于0.1″观测精度目标所需条件和特征。 相似文献
5.
Akihiro Doi Yusuke Kono Kimihiro Kimura Satomi Nakahara Tomoaki Oyama Nozomi Okada Yasutaka Satou Kazuyoshi Yamashita Naoko Matsumoto Mitsuhisa Baba Daisuke Yasuda Shunsaku Suzuki Yutaka Hasegawa Mareki Honma Hiroaki Tanaka Kosei Ishimura Yasuhiro Murata Reiho Shimomukai Shoko Koyama 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):779-793
The balloon-borne very long baseline interferometry (VLBI) experiment is a technical feasibility study for performing radio interferometry in the stratosphere. The flight model has been developed. A balloon-borne VLBI station will be launched to establish interferometric fringes with ground-based VLBI stations distributed over the Japanese islands at an observing frequency of approximately 20?GHz as the first step. This paper describes the system design and development of a series of observing instruments and bus systems. In addition to the advantages of avoiding the atmospheric effects of absorption and fluctuation in high frequency radio observation, the mobility of a station can improve the sampling coverage (“uv-coverage”) by increasing the number of baselines by the number of ground-based counterparts for each observation day. This benefit cannot be obtained with conventional arrays that solely comprise ground-based stations. The balloon-borne VLBI can contribute to a future progress of research fields such as black holes by direct imaging. 相似文献
6.
Hiroaki Kobayash Yusuke Maru Motoyuki Hongoh Shinsuke Takeuchi Keiichi Okai Takayuki Kojima 《Acta Astronautica》2007,61(11-12):978-988
This paper proposes a new aerodynamic device, which was designated multi-row-disk (MRD). This device has a cone and stabilizer disks being arranged in the axial direction. This device can arbitrarily change its aerodynamic characteristics by translating stabilizer disks. In the first part of this paper, the effect of several nose shape configurations including the MRD device on the aerodynamic characteristics is reported. By increasing the number of stabilizer disks, zero-lift drag and induced drag can be reduced. It was also found that putting cavities on the conical surface is effective for improving longitudinal static stability. In the second part, the effect of cavity flow instability on pressure and strain oscillation is reported. We drew the design criterion that the configuration of stabilizer disks should be determined not to couple the 1st mode with pressure oscillation frequency, which can be predicted with Rossiter's formula. 相似文献
7.
Takeshi Imamura Takahiro Iwata Zen-ichi Yamamoto Nanako Mochizuki Yusuke Kono Koji Matsumoto Qinghui Liu Hirotomo Noda Hideo Hanada Koh-ichiro Oyama Alexander Nabatov Yoshifumi Futaana Akinori Saito Hiroki Ando 《Space Science Reviews》2010,154(1-4):305-316
Radio occultation observations of the electron density near the lunar surface were conducted during the SELENE (Kaguya) mission using the Vstar and Rstar sub-satellites. Previous radio occultation measurements conducted in the Soviet lunar missions have indicated the existence of an ionosphere with peak densities of several hundreds of electrons per cubic centimeters above the dayside lunar surface. These densities are difficult to explain theoretically when the removal of plasma by the solar wind is considered, and thus the generation mechanism of the lunar ionosphere is a major issue, with even the validity of previous observations still under debate. The most serious error source in the measurement is the fluctuation of the terrestrial ionosphere which also exists along the ray path. To cope with this difficulty, about 400 observations were conducted using Vstar to enable statistical analysis of the weak signal of the lunar ionosphere. Another method is to utilize Vstar and Rstar with the second one being used to measure the terrestrial ionosphere contribution. The observations will establish the morphology of the lunar ionosphere and will reveal its relationship with various conditions to provide possible clues to the mechanism. 相似文献
8.
Hideo Hanada Takahiro Iwata Qinghui Liu Fuyuhiko Kikuchi Koji Matsumoto Sander Goossens Yuji Harada Kazuyoshi Asari Toshiaki Ishikawa Yoshiaki Ishihara Hirotomo Noda Seiitsu Tsuruta Natalia Petrova Nobuyuki Kawano Sho Sasaki Kaori Sato Noriyuki Namiki Yusuke Kono Kenzaburo Iwadate Osamu Kameya Katsunori M. Shibata Yoshiaki Tamura Shunichi Kamata Yukihiro Yahagi Wataru Masui Koji Tanaka Hironori Maejima Xiaoyu Hong Jinsong Ping Xian Shi Qian Huang Yusufu Aili Simon Ellingsen Wolfgang Schlüter 《Space Science Reviews》2010,154(1-4):123-144
The Japanese lunar explorer SELENE (Kaguya), which was launched on September 14th, 2007, was the target of VLBI observations over the period November 2007 to June 2009. These observations were made in order to improve the lunar gravity field model, in particular the lower degree coefficients and the model near the limb. Differential VLBI Radio sources, called VRAD instruments, were on-board the subsatellites, Rstar (Okina) and Vstar (Ouna), and the radio signals were observed by the Japanese VERA (VLBI Exploration of Radio Astrometry) network, and an international VLBI network. Multi-frequency and same-beam VLBI techniques were utilized and were essential aspects of the successful observing program. Multi-frequency VLBI was employed in order to improve the accuracy of the orbit determination obtained from the phase delay from the narrow-band satellite signals, while the same-beam VLBI method was used to resolve the cycle ambiguity which is inherent in the multi-frequency VLBI method. The observations were made at three S-band frequencies (2212, 2218 and 2287 MHz), and one X-band frequency (8456 MHz). We have succeeded in correlating the recorded signals from Okina/Ouna, and we obtained phase delays with an accuracy of several pico-seconds at S-band. 相似文献
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