2010 Vol. 30, No. 1

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2010, 30(1): 1-8. doi: 10.11728/cjss2010.01.001
Abstract(2215) PDF 683KB(1416)
Abstract:
Due to the application requirement of high layer atmosphere density model and ionosphere model, the forecast method research of 10.7 cm solar radio flux (F10.7 index) is one of the important subjects. The middle term forecast of F10.7 is more difficult than the long term and short term forecast because of the lack of comprehending physical progress and the laws of solar active region revolution. The main middle term forecast methods of F10.7 are time-sequence model and empirical model in consideration of observational information of solar active region. In this paper, autoregression method was applied to the F10.7 27-day forecast research. The period of forecast experiment was from May 1, 1996 to April 12, 2007. According to the results of forecast error analysis, the prediction precision was satisfying when solar activity was low and F10.7 showed obvious 27-day periodic tendency, but was unsatisfying when large region appeared on the disk or disappeared from the disk rapidly. Compared with the forecast result of American Air Force (AAF) forecast from September 21, 2005 to June 7, 2006, the prediction Accuracy of autoregression method was similar to that of AAF. From all of these, we can see this linear predictive method could reflect F10.7 27-day periodicity, and was applicable for F10.7 27-day forecast in a certain extent. The research result in this paper is a basis of the further work of constructing precise model of F10.7 middle term forecast.
2010, 30(1): 9-16. doi: 10.11728/cjss2010.01.009
Abstract(2276) PDF 702KB(1088)
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On Oct. 12, 2004, the Geotail spacecraft was located in the solar wind near the dayside magnetopause and observed sustaining southward IMF from 01:30UT to 04:30UT. During the interval, a weak storm is driven with minimum Sym-H index of -33 nT at 04:12UT. In the main phase of the storm, AE index had been kept at a high level with a maximum value of about 400nT. The TC-1 satellite located at (-10.6, 3.2, -0.1) Re observed evident characteristics of substorm expansion phase and the process of magnetic field dipolarization at the near-Earth magnetotail during 02:00---03:00UT. Prior to the dipolarization, tailward flow (vx<-100km/s) lasting over 3min with the characteristics of high hot ion temperature, low density and flowing along the magnetic field occurred. The features of the tailward flow indicated that it was originated from the ionosphere. During the interval of tailward flow, both the Bx component and the intensity of the magnetic field had been enhanced which suggested that the tailward flow had certain effects on the magnetic field configuration. According to the TC-1 observations, near-Earth tailward flow may be in close relation with the process of the magnetic field dipolarization.
2010, 30(1): 17-22. doi: 10.11728/cjss2010.01.017
Abstract(2455) PDF 517KB(1088)
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Using substorm AL index, substorm AE index and field-aligned current AF index in 2004, distribution of substorm AL, AE and AF onsets are studied with respect to substorm auroral onset. It is found that with auroral onsets being zero time, AL and AE onsets are mainly distributed between -5 and +6 minute, with only few exceptions between -9 and +9 minute. Field-aligned current AF onsets have a broader distribution from -8 to +7 minute. The average time differences of AL, AE, AF onsets are 0.5, 0.5, and -0.1 minute. The most probable AL onset is almost simultaneous with auroral onset, but the most probable onsets of AE and AF are about 1 min prior to auroral onsets. For those intense substorms, the onsets of AL, AE and AF approach to auroral onsets. For the five largest substorms, the onsets of AL and AE precede auroral onsets, suggesting during super substorms, substorm electric jet begin to increase before auroral breakup.
2010, 30(1): 23-28. doi: 10.11728/cjss2010.01.023
Abstract(3011) PDF 476KB(1193)
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Using the data observed with DPS-4 ionosonde from February 2002 to December 2007, influence of geomagnetic storm on the ionospheric Spread-F (SF) in Hainan region is statistically studied. The result shows that the occurrence of spread-F as a whole is suppressed by the storm. But for the different type of SF, influences of the storm are different. During storm time, FSF is motivated in 2002 and 2003, and suppressed during 2004---2007; RSF is suppressed during 2002---2005, and motivated in 2006 and 2007; MSF is suppressed in 2002, motivated in 2003 and 2004, and suppressed again during 2005---2007; SSF is suppressed during 2002---2004, motivated in 2005 and 2006, and weakly suppressed in 2007. These results are important to study the mechanism for different type of ionospheric SF during the storm time in the low latitude region.
2010, 30(1): 29-34. doi: 10.11728/cjss2010.01.029
Abstract(2399) PDF 549KB(1044)
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A number of observations showing enhanced ion acoustic echoes observed in the topside auroral ionosphere by means of both the EISCAT and Millstone Hill radars have been reported in the literature. The received power, often asymmetric, is extremely enhanced by up to 1 or 2 orders of magnitude above usual values, and it is mostly contained in one of the two ion acoustic lines. The instability processes have been proposed in many literatures to explain these phenomena, and one of the theories is the ion-ion two-stream instability theory, which is driven by large relative drifts between two or more ion species, for example O+ and a beam of H+. As long as the drift velocity is of the order of the species thermal velocity, the ion acoustic fluctuation level can be enhanced well above the thermal level, leading to an enhancement in one or both ion lines. The high relative drifts require a sufficient acceleration of H+, which might be possible at high altitudes. In this paper, the low energy H+ ion precipitation and the O+ ion outflow events are considered. The H+ ion distribution function described by the bi-Maxwellian contains the field-aligned heat flow, then the enhanced ion acoustic echoes can be interpreted using the ion-ion two-stream instabilities. The asymmetry is weakened due to the consideration of field-aligned heat flow.
2010, 30(1): 35-42. doi: 10.11728/cjss2010.01.035
Abstract(1969) PDF 577KB(1025)
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Now total atmospheric ozone amount derivation from the solar ultraviolet radiation backscattered from Earth measured by satellite has been one of the main methods to obtain total ozone amount data. Based on simulating calculation results, the paper studies and discusses the parameters which would influence the retrieval of total ozone amount arising from instrument errors and academic calculation errors, then quantificationally calculates the retrieval errors of total ozone amount induced by atmospheric radiative transfer model calculation errors, retrieval algorithm errors and instrument errors. The results obtained are very important for the precision improvement of total ozone amount retrieval and are directive for the disposal of the true datum obtained from FY-3A total ozone unit(FY-3A TOU) in the future.
2010, 30(1): 43-48. doi: 10.11728/cjss2010.01.043
Abstract(3005) PDF 495KB(1127)
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Three fragmentations with different degrees had occurred successively for Russian Cosmos 2421 satellite in the first half of year 2008 which produced several hundreds debris. This paper analyzed the three fragmentations and fragmentation debris orbit distribution, velocity increment distribution, area-to-mass ratio and their lifetime according to two-line elements data of Cosmos 2421 satellite and its debris, also made risk evaluation of fragmentation debris to spacecrafts. The results indicate that the three fragmentation dates were March 14, April 28 and June 9 respectively. The fragmentation debris were distributed within 200~1400 km altitude range. The three velocity increments mean values of fragmentation debris in space due to Cosmos 2421 satellite breakup were -8.4 m/s, 8.6 m/s, -8.3 m/s respectively. The lifetime of 67 percent fragmentation debris were within one year. Space debris density below 500 kilometers increased because of the breakup event which affected the manned spacecrafts. It can be seen by analyzing the Cosmos 2421 satellite fragmentation events that breakup events characteristic can be concluded by fragmentation debris characteristic, and the effects to the future launch activity and in-orbit satellite due to breakup events can be evaluated by space density and lifetime computation of fragmentation debris.
2010, 30(1): 49-54. doi: 10.11728/cjss2010.01.049
Abstract(2391) PDF 708KB(1222)
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FY-3A satellite was launched in June 2008 into solar synchronization orbit (about 800 km altitude). There are detectors that can measure 3~300 MeV high energy proton and 0.15~5.70 MeV high energy electrons on FY-3A satellite to carry out long-time space particles environment measurement. During the period from 2008 to 2009, space environment is very quiet because of low solar activities. The detection results on FY-3A satellite shows that flux of 3$\sim$300\,MeV high energy protons mainly are confined to SAA, whereas flux of electrons are located in SAA and around the north and south poles. The result also shows that the flux of energetic particles is to be highly anisotropic. By combining the detection result from FY-3A satellite with that from NOAA satellites, we can also find there exit differences between the detecting data from the two series of satellites not only in the space distribution of particles but also in the intensity of particles. These show the flux of energetic particles is to be highly anisotropic influenced by different pitch angles. Considering the difference of the particles flux and distribution induced by limits of time and space, even and the different designs between the detectors on the two satellites, we compared the protons and electrons detection results from FY-3A with those from NOAA satellites. A generally good agreement is observed in the flux values and distribution trend of protons and electrons. All the above indicates the detectors on FY-3A satellite have the ability to measure space energy particles. The detection results are now available, so that we can use the data from FY-3A satellite to further study radiation belt particles distribution, origin and transmission.
2010, 30(1): 55-59. doi: 10.11728/cjss2010.01.055
Abstract(2295) PDF 588KB(1021)
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A new fully automatic sounding system of middle atmosphere which succeeded in employing GPS positioning of 1680 MHz telemetry system has been introduced. Composed of balloon-borne sensors as well as ground tracking and signal processing equipments, the system has replaced the original radar or theodolite with GPS to track the radiosonde with no limitation of low elevation angle. Meanwhile, wide lobe antenna and low-noise receiver have been utilized to avoid losing the target. With this sounding system, the atmospheric electric field sounding experiments were conducted and satisfactory results have been obtained. Attributing to its portability, easy operation, low cost and favorable maneuverability and reliability, this sounding system is quite prospective for application in the near space environment detection, middle atmosphere scientific experiments and conventional meteorologic sounding as well.
2010, 30(1): 60-65. doi: 10.11728/cjss2010.01.060
Abstract(2037) PDF 613KB(1257)
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Meteor Burst Communication (MBC) is different from traditional communications. It is a low data rate communication with characteristics of burst, discontinuity and unfixed timing. It is necessary to construct prediction model of MBC channel due to its complexities. The Sporadic Meteor Radiant Distribution (SMRD), the usable Meteor Rate (MR) and Duty Cycle (DC) are important factors impacting channel of the MBC links. SMRD varies with seasons and time, therefore it is very crucial to accurately predict the SMRD to change the direction of antennae and improve the data rate. Furthermore, the correct model of MBC channel can be constructed if MR and DC are accurately predicted. By investigating the development of the modeling of meteor radiant distributions, the geometry relationship of the heliocentric and the geocentric space of sporadic meteor is constructed. The theoretic prediction models of Meteor Burst Communication (MBC) channel parameters are derived. These models are applied in MBC links. The results predicted by these models have good agreement with observation data. The prediction models of these channel parameters given herein can be helpful to construct meteor communication system.
2010, 30(1): 66-72. doi: 10.11728/cjss2010.01.066
Abstract(2098) PDF 574KB(1268)
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The Component Synthesis active Vibration Suppression method (CSVS) can be applied to suppress the vibrations of flexible systems. In this method, several same or similar time-varying component forces are arranged according to certain rules along the time axis. The resulted synthesized force can be adopted as system input, and it can suppress the arbitrary unwanted vibration harmonics while achieving the desired rigid body motion. For a kind of spacecrafts with constant amplitude reaction jet actuators, the time optimal maneuver control commands corresponded with the roles of CSVS method were converted into form of constant amplitude torque using Pulse Width Modulation (PWM). The time optimal large maneuver control strategies are designed as well. Simulation results verified the availability of this method.
2010, 30(1): 73-78. doi: 10.11728/cjss2010.01.073
Abstract(1801) PDF 741KB(1166)
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Active vibration isolation system applied to microgravity vibration isolation has utilized Lorentz force electromagnetic actuator to realize the levitation of isolated platform in the space. The Dynamic Analysis of the Electromagnetic Actuator (DAEA) is the basis of design and experiments. In this study, a structure of the actuator was presented, the finite element analysis of the permanent magnet part was implemented and the mechanical feature was validated. With the establishment of electromagnetic actuator model, the finite element analyses have been conducted, which includes static force feature analysis, implement modal analysis, transient analysis, harmonic response analysis and spectrum analysis as well. These analyses have paved the way for system structure optimization and actuator size reduction as to decrease the development cost, shorten the designing period and promote the product quality.
2010, 30(1): 79-84. doi: 10.11728/cjss2010.01.079
Abstract(2001) PDF 978KB(1248)
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Experimental study of a proportional deployable truss antenna model is presented. The experimental scheme was discussed. The motioning acceleration of measuring nodes was gathered during movement. Then the experimental result was compared with the analytical result using the program based on the Moore-Penrose generalized inverse matrix theory. The reliability of the generalized inverse matrix theory to analyze this kind of structures was proved.
2010, 30(1): 85-90. doi: 10.11728/cjss2010.01.085
Abstract(2222) PDF 456KB(1591)
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The navigating method for XNAV (X-ray pulsar-based Navigation) is similar the one of the Differential GPS (DGPS). In order to position and navigate the spacecraft (or satellite), the two Time of Arrival (TOA) from one X-ray pulsar to both the spacecraft and the solar system barycenter are demanded respectively. The difference between the two TOA is generally called the transformation equation of time. But the existent transformation equation of time is not good enough. In this paper, improvements have been made on some current expressions. The time difference between photon arrival at the observation spacecraft and solar system barycenter in XNAV is presented. It is based on the post-Newtonian approximation spacetime theory in GTR and the neglection of celestial bodies spin of the solar system as well as the effect of eccentric orbit. These considerations are reasonable under the condition that the precision of measure time magnitude is in the order of the nanosecond. The transformation of the proper time from observation spacecraft to BCT (Barycentric Coordinate Time) is also obtained. Based on this relation, a proposal is presented that the frequency of clock at spacecraft can be adjusted in the same way as GPS.
2010, 30(1): 91-96. doi: 10.11728/cjss2010.01.091
Abstract(2990) PDF 730KB(1328)
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TDI (Time Delay and Integration) CCD camera has been used widely in space-based reconnaissance. But this kind of camera introduces large amounts of image smear. To analyze the image smear sources, a space TDI CCD mathematical model which scans the camera pixels corresponding relations with the point of scenery was established. It can be used to reckon cumulating image smear where the TDI CCD imaging exceeded the corresponding pixel horizontal and vertical offset. Based on the space TDI CCD mathematical mode, a TDI CCD camera imaging emulator software is developed with VC++ 6.0. To provide a real satellite TDI CCD imaging simulation space environment for the emulator software, a satellite attitude control single-axis simulation flotation was established. The TDI CCD camera imaging emulator software and the satellite attitude control single-axis simulation flotation constitute the real-time space TDI CCD camera imaging simulation platform, which can dynamically simulates the real-time effect of satellite attitude error to the image process of space TDI CCD camera imaging with nominal deviant angle adjustment. Simulation results show that the angular velocity of yaw angle has the greatest impact on image quality, and roll attitude angle almost has no effect on image quality, which are consistent with the real TDI CCD image.