单星导航HEO卫星初轨确定算法

HEO(Highly Elliptical Orbit)轨道卫星利用星载GPS(Global Positioning System)进行自主定轨面临的主要难题之一就是解决在单颗导航卫星条件下的初轨确定问题.从理论上分析了利用单颗导航卫星的观测量确定HEO卫星轨道初值的所需满足的条件,指出了利用F.G级数法求解初值存在的问题,提出了一种基于轨道根数约束的迭代批处理算法,该算法无需复杂的数学运算,避免了F.G级数法用短弧资料定初轨时系数矩阵秩亏的影响.仿真结果表明,当先验轨道根数误差在允许范围内取值时,在考虑轨道射入误差的情况下,初值的位置偏差在10⁴ m量级,速度偏差在10⁰ m/s量级,能够根据单颗导航卫星的短弧观测值可靠地完成轨道初值的确定.     

星网融合天地一体面向农村

20 0 0年 ,以蜂窝通信巨人克雷格·麦考 (Crag Mc Caw)为主要投资者的Teledesic公司 ,收购濒临破产的中圆轨道卫星 (ICO)公司后 ,对原先经营全球卫星移动电话的 ICO公司及其业务曾进行了战略重组。该公司首先投巨资重新设计和改进ICO卫星系统 ,将其市场定位从传输窄带话音 (移动电话 )业务为主转变为传输比较高速的数据业务为主。铱星公司和老 ICO公司均将它们的卫星业务定位在为全球大众消费者和商务旅行者提供窄带移动电话业务上。错误的市场定位和市场预测导致重大的决策失误 ,造成在错误的时间、错误的市场向错误的消费对象推出…     

基于卫星寿命末期燃料计算偏差分析的寿命预测方法

针对PVT方法计算剩余燃料偏差大影响卫星在轨任务规划的问题,提出一种基于输入参数偏差分析的卫星剩余燃料估计和修正方法.在推导剩余燃料估计误差传播方程和比对记账法、PVT法计算偏差的基础上,开展PVT法计算剩余燃料的误差源和输入偏差分析,对卫星剩余燃料进行修正.在仅考虑剩余燃料影响的前提下,建立地球静止轨道(GEO)卫星在轨燃料消耗预测模型,预测GEO卫星剩余寿命.实际工程应用表明：该方法在卫星剩余燃料计算出现较大偏差时,能够较好地修正计算偏差,可为卫星在轨任务规划提供技术支撑及参考借鉴.     

人造卫星的动静平衡试验和误差分析

本文着重介绍了人造卫星静、动平衡试验的目的、试验的原理和设备。我们专门设计了供垂直状态进行静平衡的试验设备,克服了卫星平衡试验时的挠度问题。对现有通用动平衡机进行改装,满足了卫星平衡试验对转速等的要求。并根据卫星本身无平衡轴、装夹困难、结构刚性差、要求配重尽量少而轻、平衡精度很高的特点,合理地确定了卫星悬臂平衡试验方案。通过反复试验和分析,找到了悬臂平衡时的配重规律,结合我国第一颗人造卫星的结构特点采用了大部件与整体分开进行平衡及三个配重面分别平衡的方案,使配重合理分布,解决了配重空间、位置限制及动力变形等问题,利用改装后的动平衡机能无级变速的特点,采用在动平衡机上低速静平衡、高速动平衡的方法,既省去了专用静平衡设备,又简化了操作,缩短了试验周期。最后,对试验中的各项误差分别进行了实验测定和仔细的分析计算,这些完全满足了卫星的平衡精度要求,使卫星达到了预期的飞行目的。     

飞行器质心偏差极限值计算方法研究

针对飞行器的质心偏差极限值问题,首先经推导给出了质心偏差的理论计算公式,通过对理论公式的分析指出了其不足,随后分析了质心偏差极限值分析的穷举法、蒙特卡洛方法和最优化方法,最后针对一种典型飞行器,对各种方法进行了实例分析.通过对计算结果的讨论,说明蒙特卡洛方法对偏差的分布较为有效,而穷举法和最优化方法对偏差极限值分析效果...     

深空探测器在轨推力器参数辨识方法

针对中国首次自主火星探测任务需要,结合环绕器质量特性和推进系统布局构型,分析了喷气卸载对整器角动量的影响。在分析的基础上,通过飞轮卸载前后三轴转速变化规律,计算整器角动量变化情况,并解算出每次喷气时产生的冲量及推力方向偏差;通过同组推力器作用时对各轴的扰动,解算整器质心坐标。利用在轨数据分析了天问一号探测器巡航段6次使用不同推力器的喷气卸载情况,解算的推力器方向偏差、质心坐标和地面设计值进行比对,实测推力方向偏差不超过0.6°,质心绝对偏差小于18mm,验证了计算方法的有效性和正确性,可作为后续轨控任务的点火方向制定、燃料预算的输入依据。     

基于GNSS测量的天宫二号质心确定

由于轨道机动燃料消耗,科学载荷加载、分离,以及伴飞小卫星在轨释放等原因引起天宫二号空间站质心(COM)发生位移,从而影响天宫二号的动力学质心定轨精度。针对这一问题,提出了基于全球导航卫星系统(GNSS)测量数据的简化动力学质心估计方法。燃料消耗是引起天宫二号质心发生位移的主要原因,质心在本体坐标系X轴方向位移最为显著。利用GNSS测量数据对天宫二号进行质心估计和精密定轨,在三轴对地稳定姿态下,本体坐标系X轴方向与轨道切向重合,定轨结果对本体坐标系X轴方向的质心位移并不敏感。但在连续偏航模式下,本体坐标系X轴在轨道法向上有较大分量,X轴方向的质心位移对基于GNSS测量计算的精密定轨结果有较大影响。定性和定量分析结果表明:偏航姿态模式下天宫二号本体坐标系X轴方向质心位移估计具有可行性。天宫二号实测数据计算结果表明:与未做质心估计的定轨结果进行对比,质心估计后表征轨道动力学建模误差的经验加速度补偿水平在轨道径向、切向和法向上分别降低62%、50%和65%;载波相位后验残差标准差降低0.04 cm;精密轨道与全球激光测距数据比较精度提高0.86 cm。所提方法可以应用于大型低轨航天器在轨质心估计。      

GPS P(Y)码功率增强监测分析

全球定位系统(GPS)的Block IIR-M和Block IIF卫星具备可编程功率输出能力, 可以灵活增强单个信号分量的发射功率。为了系统评估GPS P(Y)码的功率增强能力, 对弹性功率的原理进行了理论分析, 提出了GPS信号功率增强的监测分析方法, 利用国际GNSS监测评估系统(iGMAS)和国际GNSS服务(IGS)监测站数据、高增益天线监测数据、事后精密星历对GPS增强P(Y)码的覆盖性及星座性能、空间信号和用户端性能进行了分析。结果表明:在保持发射总功率和民用信号功率不变的情况下, Block IIF和Block IIR-M卫星的L1 P(Y)码和L2 P(Y)码功率相比正常水平分别增强约6 dB和5 dB;在功率增强信号覆盖区内仅利用19颗增强卫星进行双频单点定位, 位置误差不大于15 m(95%);当可见增强卫星数为6, 增强后的P(Y)码载噪比为55 dB·Hz时, P(Y)码之间的多址干扰引起的等效载噪比下降量为0.4 dB。      

基于STLS的卫星质量质心在轨估计

提出了一种使用结构总体最小二乘(Structured Total Least Squares,STLS)进行卫星质量和质心参数在轨估计的方法。其相对于现有方法有三个优点:采用完整的动力学模型,考虑敏感器测量误差,估计模型中不包含误差很大的推力值。首先推导了卫星质量和质心参数的估计方程,将其化为STLS模型的形式,对该模型定义了质量质心参数的STLS估计,并使用结构总体最小范数(Structured Total Least Norm,STLN)算法进行具体求解。证明了当敏感器噪声为高斯分布时,该估计为极大似然估计。仿真结果验证了该STLS估计方法的有效性。     

基于参考轨道的Walker星座相对相位保持策略

针对高轨道Walker全球星座相对相位保持问题,在分析星座几何结构演化规律基础上,提出了一种基于动态调整参考轨道的星座相对相位保持策略.该参考轨道的半长轴取星座所有卫星的平均轨道半长轴的平均值,通过计算各卫星相对参考轨道的相对相位偏差以及变化率,而后根据有关维持的约束条件来选择合适的卫星进行站点保持,使得所有卫星的相对参考轨道的相位偏差不超过允许值.当一旦有卫星进行了站点保持,则参考轨道就重新统计确定.文章通过一个12颗MEO卫星构成的Walker-δ星座的分析算例,表明这种相对保持策略可以减少星座的站点维持次数.本文提出的方法可以为我国今后卫星导航星座的维持提供参考.     

不同粒径组合对植物栽培基质容重及孔性和水吸力的影响

研究粒径对栽培基质容重、孔性和水吸力的影响,以便为空间植物培养提供栽培基质。采用4种基质,即Profile基质（P）、黑陶粒（B）、白陶粒（W）和蛭石（V）,各基质按照不同粒径（< 1 mm,1~2 mm,2~3 mm）组成设置了10种组合（体积百分比）,研究测试不同粒径组合基质的基本理化特性、容重、孔性和水吸力。P和B基质的容重约0.70 g·cm–3。P基质含有较多矿质养分离子;增加小粒径基质颗粒占比,不同组合基质的容重、总孔隙度和持水孔隙度均显著增加,但通气孔隙度下降;在10种不同基质组合中,P7（40-60-0）、B8（10-70-20）和W4（10-60-30）分别具有最高的总孔隙度,P8（10-70-20）,B1（20-50-30）和W8（10-70-20）具有最高的气水比,P3（50-50-0）,B3（50-50-0）和W3（50-50-0）具有最高吸附水量;4种基质的平均总孔隙度和吸水量大小顺序为V>P>B>W。因此,P3（50-50-0）基质和B7（40-60-0）基质具有适中的容重、良好的孔性和较高的水吸力,适用于空间植物栽培。      

Interaction of growth-determining systems with gravity

The experiments have been carried out with lettuce shoots on board the Salyut-7 orbital station, the Kosmos-1667 biological satellite and under ground conditions at 180° plant inversion. By means of the centrifuge Biogravistat-1M the threshold value of gravitational sensitivity of lettuce shoots has been determined on board the Salyut-7 station. It was found to be equal to 2.9 × 10⁻³g for hypocotyls and 1.5 × 10⁻⁴g for roots. The following results have been received in the experiment performed on board the Kosmos-1667 satellite: a) under microgravity the proliferation of the meristem cells and the growth of roots did not differ from the control; b) the growth of hypocotyls in length was significantly enhanced in microgravity; c) under microgravity transverse growth of hypocotyls (increase in cross sectional area) was significantly increased due to enhancement of cortical parenchyma cell growth. At 180° inversion in Earth's gravity root extension growth and rate of cell division in the root apical meristem were decreased. The determination of DNA-fuchsin value in the nuclei of the cell root apexes showed that inversion affected processess of the cell cycle preceeding cytokinesis.     

Midday bottomside electron density profiles during moderate solar activity and comparison with IRI-2001

Bottomside electron density (Ne-h) profiles during midday (10–14 h) are analyzed using modern digital ionosonde observations at a low-middle latitude station, New Delhi (28.6N, 77.2E, dip 42.4N), for the period from January 2003 to December 2003, pertaining to moderate solar activity (MSA). Each individual profile is normalized with respect to the peak height and density (hmF2, NmF2) of the F2-region. These profiles are compared with those obtained from the International Reference Ionosphere (IRI-2001) model. Bilitza [Bilitza, D. International Reference Ionosphere 2000. Radio Sci. 36 (2), 261–275, 2001] using both the options namely: Gulyaeva’s model [Gulyaeva, T.L. Progress in ionospheric informatics based on electron density profile analysis of ionograms. Adv. Space Res. 7 (6) 39–48, 1987] and B0 Tab. option [Bilitza, D., Radicella, S.M., Reinisch, B.W., Adeniyi, J.O., Mosert Gonzalez, M.E., Zhang, S.R., Obrou, O. New B0 and B1 models for IRI. Adv. Space Res. 25 (1), 89–95, 2000]. The study reveals that during summer and equinox, the IRI model with B0 Tab. option in general, produces better agreement with the observed median profiles, while the IRI predictions using Gulyaeva’s option, overestimate the electron density distribution at all the heights below the F2-peak. However, during winter, in general, the IRI model, using both the options, reveals shows fairly good agreement with the observations.     

On the non-occurrence of Type I X-ray bursts from the black hole candidates

It has been justifiably questioned if the black hole candidates (BHCs) have “hard surface” why Type I X-ray bursts are not seen from them [Narayan, R., Black holes in astrophysics, New J. Phys, 7, 199–218, 2005]. It is pointed out that a “physical surface” need not always be “hard” and could be “gaseous” in case the compact object is sufficiently hot [Mitra, A., The day of the reckoning: the value of the integration constant in the vacuum Schwarzschild solution, physics/0504076, p1–p6, 2005; Mitra, A., BHs or ECOs: A review of 90 years of misconceptions, in: Focus on Black Holes Research, Nova Science Pub., NY, p1–p94, 2005]. Even if a “hard surface” would be there, presence of strong intrinsic magnetic field could inhibit Type I X-ray burst from a compact object as is the case for Her X-1. Thus, non-occurrence of Type I bursts actually rules out those alternatives of BHs which are either non-magnetized or cold and, hence, is no evidence for existence of Event Horizons (EHs). On the other hand, from the first principle, we again show that the BHCs being uncharged and having finite masses cannot be BHs, because uncharged BHs have a unique mass M = 0. Thus the previous results that the so-called BHCs are actually extremely hot, ultramagnetized, Magnetospheric Eternally Collapsing Objects (ECOs) [Robertson, S., Leiter, D., Evidence for intrinsic magnetic moment in black hole candidates, Astrophys. J., 565, 447–451, (astro-ph/0102381), 2002 ; Robertson, S., Leiter, D., MECO model of galactic black hole candidates and active galactic nuclei, in: New Developments in Black Hole Research, Nova Science Pub., NY, p1–p44, astro-ph/0602453, 2005] rather than anything else get reconfirmed by non-occurrence of Type I X-ray bursts in BHCs.     

Gamma rays from accreting matter onto collapsed objects

In the spherical accretion onto massive objects, the matter may be heated up to temperatures as high as 10¹² °K. In such a hot plasma, the thermal bremsstrahlung (e-e and e-p) and π° decay from inelastic collisions of protons are the main γ-ray sources. We determined the γ -ray production spectra from the π° decay and from bremsstrahlung for different temperatures. The expected γ-ray spectra were evaluated too in order to fit experimental data. We have fitted COS B data from 3C 273 using a two temperatures plasma model. The best fit is for

Full-size image (1K)

(M₈ is the black hole mass in 10⁸ M) which gives . The hard X-ray measurements do not contradict the bremsstrahlung spectrum.     

Relativistic electrons high doses at International Space Station and Foton M2/M3 satellites

The paper presents observation of relativistic electrons. Data are collected by the Radiation Risk Radiometer-Dosimeters (R3D) B2/B3 modifications during the flights of Foton M2/M3 satellites in 2005 and 2007 as well as by the R3DE instrument at the European Technology Exposure Facility (EuTEF) on the Columbus External Payload Adaptor at the International Space Station (ISS) in the period February 20 – April 28, 2008. On the Foton M2/M3 satellites relativistic electrons are observed more frequently than on the ISS because of higher (62.8°) inclination of the orbit. At both Foton satellites the usual duration of the observations are a few minutes long. On the ISS the duration usually is about 1 min or less. The places of observations of high doses due to relativistic electrons are distributed mainly at latitudes above 50° geographic latitude in both hemispheres on Foton M2/M3 satellites. A very high maximum is found in the southern hemisphere at longitudinal range 0°–60°E. At the ISS the maximums are observed between 45° and 52° geographic latitude in both hemispheres mainly at longitudes equatorward from the magnetic poles. The measured absolute maximums of dose rates generated by relativistic electrons are found to be as follows: 304 μGy h⁻¹ behind 1.75 g cm⁻² shielding at Foton M2, 2314 μGy h⁻¹ behind 0.71 g cm⁻² shielding at Foton M3 and 19,195 μGy h⁻¹ (Flux is 8363 cm⁻² s⁻¹) behind les than 0.4 g cm⁻² shielding at ISS.     

Analysis of the space radiation doses obtained simultaneously at two different locations outside the ISS

Space weather and related ionizing radiation has been recognized as one of the main health concerns for the International Space Station (ISS) crew. The estimation of the radiation effect on humans outside the ISS requires at first order accurate knowledge of their accumulated absorbed dose rates, which depend on the global space radiation distribution, solar cycle and local variations generated by the 3D mass distribution surrounding the ISS. The R3DE (Radiation Risks Radiometer-Dosimeter for the EXPOSE-E platform) on the European Technological Exposure Facility (EuTEF) worked successfully outside of the European Columbus module between February 2008 and September 2009. A very similar instrument named R3DR for the EXPOSE-R platform worked outside the Russian Zvezda module of the ISS between March 2009 and August 2010. Both are Liulin-type detectors, Bulgarian-built miniature spectrometer-dosimeters. The acquired approximately 5 million deposited energy spectra from which the flux and absorbed dose rate were calculated with 10 s resolution behind less than 0.41 g cm⁻² shielding. This paper analyses the spectra collected in 2009 by the R3DE/R instruments and the long-term variations in the different radiation environments of Galactic Cosmic Rays (GCR), inner radiation belt trapped protons in the region of the South Atlantic Anomaly (SAA) and relativistic electrons from the Outer Radiation Belt (ORB). The R3DE instrument, heavily shielded by the surrounding structures, measured smaller primary fluxes and dose rates from energetic protons from the SAA and relativistic electrons from the ORB but higher values from GCRs because of the contribution from secondary particles. The main conclusion from this investigation is that the dose rates from different radiation sources around the International Space Station (ISS) have a large special and temporal dynamic range. The collected data can be interpreted as possible doses obtained by the cosmonauts and astronauts during Extra Vehicular Activities (EVA) because the R3DE/R instruments shielding is very similar to the Russian and American space suits average shielding (,  and ). Fast, active measurements are required to assess accurately the dose accumulated by astronauts during EVA.     

太阳风中动力论Alfven波的湍流谱(a)朗道衰减

提出一个太阳风中Alfven脉动湍流的新模式,动力论Alfven波是Alfven波和离子声波非解耦的新波模。由太阳向外传播的各种波长的动力Alfven波的非线性相互作用推导出动力论Alfven脉动湍流功率谱P_k,在Alfven半径以外,P_k∝k-3/2,而在Alfven半径以内,由太阳附近的P_k∝k-1变化成P_k∝k-3/2动力论Alfven脉动在Alfven半径以内完成朗道衰减。新模式克服了以前理论模式遇到的困难。      

Modeling and observations of the north–south ionospheric asymmetry at low latitudes at long deep solar minimum

Using the physics based model SUPIM and FORMOSAT-3/COSMIC electron density data measured at the long deep solar minimum (2008–2010) we investigate the longitude variations of the north–south asymmetry of the ionosphere at low latitudes (±30° magnetic). The data at around diurnal maximum (12:30–13:30 LT) for magnetically quiet (Ap ? 15) equinoctial conditions (March–April and September–October) are presented for three longitude sectors (a) 60°E–120°E, (b) 60°W–120°W and (c) 15°W–75°W. The sectors (a) and (b) have large displacements of the geomagnetic equator from geographic equator but in opposite hemispheres with small magnetic declination angles; and sector (c) has large declination angle with small displacement of the equators; vertical E × B drift velocities also have differences in the three longitude sectors. SUPIM investigates the importance of the displacement of the equators, magnetic declination angle, and E × B drift on the north–south asymmetry. The data and model qualitatively agree; and indicate that depending on longitudes both the displacement of the equators and declination angle are important in producing the north–south asymmetry though the displacement of the equators seems most effective. This seems to be because it is the displacement of the equators more than the declination angle that produces large north–south difference in the effective magnetic meridional neutral wind velocity, which is the main cause of the ionospheric asymmetry. For the strong control of the neutral wind, east–west electric field has only a small effect on the longitude variation of the ionospheric asymmetry. Though the study is for the long deep solar minimum the conclusions seem valid for all levels of solar activity since the displacement of the equators and declination angle are independent of solar activity.