2004 Vol. 24, No. 5

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CHARGING PROCESS OF SPACE DUST AND ITS DEPENDENCE UPON PLASMA PARAMETERS
LI Jiawei, LI Zhongyuan
2004, 24(5): 321-325. doi: 10.11728/cjss2004.05.20040501
Abstract(2474) PDF 427KB(1197)
Abstract:
Dust grains immersed in plasma will be charged of various charging currents, this paper considers three main currents due to the relative velocity between the dust grains and the plasma: the primary ions, the primary electrons, and the sec-ondary electrons. The surface potentials of silicate and carbon dusts grains in H+ and H2O+ plasma environments are calculated using universal plasma parameters, these plasma conditions are common in space environments, such as comets, plan-etary rings, and interplanetary media. A conclusion is found that the equilibrium potential of dust grains have close correlation with the plasma temperature. At low temperatures, the surface potential will become lower while the temperature rises. The dust can reach a positive potential when the temperature is high enough. The potential of carbon grains is lower than that of silicate grains. The component of plasma may affect the potential, too. For both silicate and carbon grains, potential in H+ plasma is higher than that in H2O+ plasma.
AN ANALYSIS OF THE IONOSPHERIC DISTURBANCES DURING A MAGNETIC STORM OBSERVED WITH A GPS NETWORK
XIA Chunliang, WAN Weixing, YUAN Hong, YU Tao
2004, 24(5): 326-332. doi: 10.11728/cjss2004.05.20040502
Abstract(2219) PDF 902KB(1090)
Abstract:
With a GPS network located in the East Asia and Australia sector, a anal-ysis method to estimate the rapid variation of TEC is proposed and applied to the investigation of the ionospheric responses to the July 14-18, 2000 geomag-netic storm. The analyzed result reveals the perturbation structure around the geomagnetic equator during the storm. The temporal and spatial changes of TEC are obtained and discussed. The results manifest most of the information of the storm-time regional TEC variation in spite of the disadvantageous influences, such as the asymmetrical distribution of the GPS network, the shortfall of observation data, the discontinuous variety of data and etc. It is shown that the method we used is satisfactory in studying the small scale ionospheric disturbance such as the perturbations during ionospheric storms.
CHARACTERISTICS OF GRAVITY WAVE SPECTRUM IN THE WINTER MESOPAUSE REGION
WU Yongfu, XU Jiyao
2004, 24(5): 333-339. doi: 10.11728/cjss2004.05.20040503
Abstract(2569) PDF 612KB(989)
Abstract:
This paper utilizes horizontal velocity data with high resolution measured by 19 chaff rockets in the 80-105 km region during the DYANA campaign to study char-acteristics of vertical wavenumber spectrum of scalar horizontal velocity in winter. Results show that the mean vertical wavenumber spectrum in winter has a spec-tral slope of -3.02, which is quite consistent with the -3 spectral slope predicted by various saturation theories, therefore, this provides an observational evidence of a saturated gravity wave spectrum in winter. Comparison with various saturation theories shows that spectral amplitude of the winter spectrum is perfectly consistent with that spectral amplitude predicted by the linear saturation theory, but it is always lower than those spectral amplitudes predicated by the nonlinear saturation theories and measured by lidars. The winter spectrum, together with a saturated gravity wave spectrum in the polar summer obtained recently, shows collectively that our observational results support the linear saturation theory re-gardless of different seasons, different geographical locations, and different height regions. Dominant vertical wavelength of the winter spectrum is estimated to be 15km, which is slightly larger than the dominant vertical wavelength of 12.8km measured in summer.
SEMIANNUAL VARIATION OF GEOMAGNETIC Z COMPONENT AT LOW LATITUDE
MA Ruiping, XU Jiyao, JI Qiao
2004, 24(5): 340-345. doi: 10.11728/cjss2004.05.20040504
Abstract(2738) PDF 583KB(1201)
Abstract:
Using the data collected in 4 geomagnetic stations located separately at Wuhan, Guangzhou, Quanzhou and Qiongzhong in the low latitude, the difference of geomagnetic Z component (Dz) between the diurnal average value and the average value of 1100-1300 LT at 5 quiet-day in every month have calculated. The amplitude and phase of semiannual variation in every year have obtained by analyzing the 12 Dz with multiple regression method. The result shows that Dz of 4 stations all have semiannual variation in every year. The amplitude of semiannual variation is related to the solar activity, and in general, the amplitude of semiannual variation of Dz in solar maximum is obviously greater than that in solar minimum. The semiannual variation of solar activity modulates the amplitude of semiannual variation of Dz obviously. The phase of semiannual variation of Dz is in March- April (or September-October), so the maximum of Dz appears in Equinox. The semiannual variation of geomagnetic Z component at low latitude indicates that the equato-rial electrojet have semiannual variation as well. The semiannual variation of the equatorial electrojet causes the f0F2 of ionosphere to appear semiannual variation by fountain effect. And this is a reasonable mechanism to produce semiannual variation of f0F2.
KEY PHYSICAL PROBLEMS IN DEEP DIELECTRIC CHARGING ON SATELLITES
HUANG Jianguo, CHEN Dong, SHI Liqin
2004, 24(5): 346-353. doi: 10.11728/cjss2004.05.20040505
Abstract(3046) PDF 705KB(1071)
Abstract:
Deep dielectric charging (DDC) is one of the key factors inducing malfunctions and failures on geo-synchronous satellites. In this paper, the mam problems such as charging time, electric field distribution, as well as influences on DDC-induced maximum field by shield, dielectric thickness and grounding patterns are studied in detail, and some results of computer simulation are introduced for the plannar model. In the meantime, some preliminary measures for DDC protection are re-commended accordingly. The charging time depends on both dielectric parameters and flux of high ener-getic electrons in the space environment. For epoxy, a kind of usually used dielectric material on satellites, the charging time is in the order of hours. The electric field distribution in the dielectric is determined by the grounding pattern. For the case grounded on single side, the maximum field generally appears on the grounded side with the other side having zero field. While for the case grounded on both sides, both sides have maximum fields, with values smaller than single-grounded case. Moreover, the maximum field in the dielectric is related to the thickness of the dielectric itself and the applied shield. The maximum field increases with the dielectric thickness to a saturated value, and decreases with the shield thickness, however, contribution of the shield over a certain thickness is neglegible.
ANALYSIS OF THE CHARACTERISTICS OF THE TRANSFER TRAJECTORY OF LUNAR EXPLORER
ZHOU Wenyan, YANG Weilian
2004, 24(5): 354-359. doi: 10.11728/cjss2004.05.20040506
Abstract(2323) PDF 466KB(2469)
Abstract:
The characteristics of a trans-lunar trajectory affected by some parameters such as the height of perigee, trans-time and inclination of transfer trajectory is analyzed in this article. Assuming a lunar explorer is injected into the transfer trajectory from a circle earth parking orbit on 025000, 08/27/2004 and approaches perilune of 200km high forming a polar lunar orbit. Two velocity impulse at perigee and perilune are calculated. The results show that the inclination of transfer trajectory has little effect on the velocity impulse of perigee, but remarkable on the velocity impulse of perilune. A transfer trajectory with certain inclination should be chosen to the least fuel consume. The total velocity impulse will decrease with the trans-time increases. When the trans-time is longer than 90 h, the total velocity impulse varies little. But the trans-time of 120h is chosen to ensure that the spacecraft be observed at perilune. The fuel can be saved by increasing the injecting height, but the capability of launch vehicle should be considered simultaneously to decide the height.
OPTIMIZATION OF ORBIT DESIGN FOR LUNAR SATELLITE
LIN Shengyong, LI Zhuji, HE Xingsuo
2004, 24(5): 360-366. doi: 10.11728/cjss2004.05.20040507
Abstract(3033) PDF 580KB(1028)
Abstract:
Orbit design of lunar satellite is optimized by using zonal harmonics J2 and J3. First, the effects of perturbation factors are analyzed. The result shows that the primary perturbation on a low-altitude lunar satellite orbit is the moon’s nonspher-ical gravity field. Second, the formula of frozen orbit are derived in response to J2 and J3 and verified by direct integration of differential equation including only lunar gravity model. In this analysis, all other perturbations (third body perturbation, solar radiation pressure, etc.) are neglected. Finally, polar orbit design is optimized by proper selection of eo and ωo, and simulated. As a numerical result, initial val-ues of 213.49° for argument of perigee and approximately 0.0109 for eccentricity (80×120 km orbit) can limit excursions beyond the ±20 km range within about 70 d on the orbit of α=1838 km. It shows that the optimization method is very useful.
RIGID-FLEXIBLE COUPLING DYNAMICS OF SATELLITE SOLAR BATTERY
LIU Jinyang, HONG Jiazhen
2004, 24(5): 367-372. doi: 10.11728/cjss2004.05.20040508
Abstract(2334) PDF 482KB(1043)
Abstract:
In this paper, the rigid-flexible coupling dynamics of satellite solar battery with multi point contact-impact is investigated. Based on Jourdain’s variational principle and forward recursive formulation, the dynamic model of flexible multibody systems with contact impact is established. According to Hertz’s impact law, the relation between the impact force and local deformation is obtained. The contact-impact of satellite plates is simulated by using rigid model and flexible model, respectively. The time histories of the impact force, impact time are calculated to reveal the coupling of the large overall motion and deformation.
A SIMULATION OF EVA SPACE SUIT THERMAL CONTROL SYSTEM
YU Minxian, LIN Guiping, WANG Liang
2004, 24(5): 373-381. doi: 10.11728/cjss2004.05.20040509
Abstract(2221) PDF 848KB(1065)
Abstract:
In this paper, heat dissipation of the human on Liquid Cooling and Ventilation Garment (LCVG) are discussed by linking the mathematics models of human ther-mal control system, metal-hydride cold source and Liquid Cooling Garment (LCG). By simulating the EVA space suit thermal control system working condition for 5.5h, the temperatures of every part in the body, the inlet and outlet of LCG and the outlet of the metal-hydride cold source were obtained. The result might be utilized in the design of EVA space suit thermal control system and further inves-tigation.
A/D CONVERTERS’ SIGNAL-TO-NOISE RATIO ANALYSIS AND IT’S APPLICATION IN MOONLET TERMINALS
YU Chao, DUAN Dengping, WANG Jianyu, LI Guotong
2004, 24(5): 382-387. doi: 10.11728/cjss2004.05.20040510
Abstract(2397) PDF 537KB(1054)
Abstract:
The traditional moonlet narrowband receiver’s signal bandwidth is narrow, so a low sampling rate is needed and many commercial ADC products may meet this requirement. In this paper, a broadband high intermediate frequency (IF) receiving scheme is proposed for moonlet radio terminal receivers. In this scheme, intermediate frequency is designed at 70MHz, and signal bandwidth is 20MHz. Analog-to-Digital Converters (ADC) play an important role in digital communication or moonlet receivers. The sampling rate and conversion bits are the main index for ADC’s characteristics. According to the requirements mentioned above, the factors which may affect ADC’s Signal-to-Noise Ratio (SNR) characteristics are analyzed in detail, and the corresponding calculated results, such as sampling rate and conversion bits are given. In the end, the relations among the ADC’s SNR, sampling rate and conversion bits are discussed.
EFFECTS ON PHYSIOLOGICAL CHARACTERISTICS OF TUMOR CELL LINES BY SPACE ENVIRONMENT
XIANG Qing, FANG Qing, CHEN Zhihua, LI Hongyan, XU Bo, XU Mei, ZHOU Donghui, ZHAO Tiande, TANG Jingtian, CHEN Weichang
2004, 24(5): 388-393. doi: 10.11728/cjss2004.05.20040511
Abstract(2147) PDF 538KB(995)
Abstract:
To investigate the effects on physiological characteristics of tumor cell lines by space environment and inaugurate a new pathway of immune therapy in cancer, three tumor cell lines were carried in the returning module of spacecraft launched by Shenzhou-4 (SZ-4). Three cell lines were returned after 7 days’ flying in space. All survival cells were monocoloned and the cell cycle, morphology, adhesive force and expression of cytokines were studied. The cell cycle of mouse melanoma B16 cells was changed after the flight. Comparing with the control group on the ground, the cell number of G1 phase was increased markedly (p < 0.05). With that simulta-neously, B16 cells showed multiple cell morphological changes. Adhesion to vascular endothelial cell was decreased in human lung carcinoma L78 cells, however, it was enhanced after passage for 2-3 times in L78 cells. The expression of cytokine IL-2, IL-8, TNF and TGF were improved in human cervical carcinoma Caski cells. In contrast, the expression of these cytokines was reduced in L78 cells. All these results revealed that physiological function of tumor cells were affected by the space environment. Whether the immunity was strengthened in tumor cell should be further studied.
GIBBERELLINS MEDIATE THE DEGRADATION OF STARCH GRAINS INDUCED BY SIMULATED MICROGRAVITY IN CARROT CALLUS CELLS
CUI Dayong, CAI Weiming, TANG Zhangcheng
2004, 24(5): 394-400. doi: 10.11728/cjss2004.05.20040512
Abstract(2108) PDF 719KB(968)
Abstract:
Microgravity environment in space affects organism. The biological effects of microgravity have been used a clinostat to simulate. The clinostat treatment induced the increase of gibberellins (GAs) and the activity of total amylase (especially the increment of a-amylase activity), as well as the degradation of starch grains in carrot callus cells. The increment trend of GAs and α-amylase activity was con-sistent. Further more, ancymidol, the inhibitor of the biosynthesis of GAs could remarkably repress the increment of α-amylase activity induced by the clinostat treatment. Therefore, we deduce that clinostat treatment can stimulate the raise of GAs, which induces the increment of the expression of α-amylase genes, then trig-gers the degradation of starch grains. As a result, plant can produce more active energy to respond to clinostat stimulus.