近地轨道卫星太阳电池阵功率衰减估计

针对LEO(Low Earth Orbit,近地轨道)卫星的太阳电池阵输出功率衰减问题,在分析卫星轨道半长轴、太阳入射角、日地距离等参数变化与影响的基础上,提出按照轨道衰减快慢来区分太阳活动高年与低年,进而通过区分高年与低年,再根据不同季节分别进行太阳电池阵输出功率的衰减估计,而无须做功率归一化。同时,重点关注了夏至前后的最低输出功率的衰减情况,以此作为在轨卫星长期管理中的能源参考,建立平均电流和功率衰减因子估计模型,并结合实际工程数据进行了衰减估计。结果表明,太阳电池阵输出功率的年衰减因子约为-0.012,年衰减率约为1.2%。该结果可应用于在轨卫星长期管理的遥测诊断辅助。     

北斗GEO卫星南北控制对半长轴影响分析

在北斗GEO（Geostationary Earth Orbit,地球静止轨道）卫星南北控制期间,陀螺漂移、姿态控制、轨道平面变化等因素都会对卫星轨道半长轴产生影响,进而影响卫星星下点经度漂移,而在实际工程中难以提前准确预估南北控制对半长轴的影响。根据GEO卫星南北控制特点,分析了各因素对半长轴影响的原因,通过影响因素剥离的方法建立了各因素对半长轴影响的模型,利用在轨GEO卫星历次南北控制的实际数据,验证了模型的准确性并给出了各个因素的影响量级。结果表明,该模型可使得南北控制对半长轴影响的预测精度达到1 km以内,可用于北斗GEO卫星南北控制时半长轴补偿控制。     

对地观测卫星调度的混合整数规划模型及求解

首先简要介绍对地观测卫星的成像过程,详细分析多星调度过程中涉及的各种约束。在此基础上,将对地观测卫星调度问题看作一类具有时间窗口的并行机器调度问题,对其进行了数学描述,并建立对地观测卫星调度的混合整数规划模型。采用列生成法,将多卫星调度问题分解为集合分割主问题和单卫星调度子问题,通过循环迭代来求解调度模型。最后,针对本文提出的算法设计一个问题实例,并给出算法计算结果。结果分析表明,列生成法的效率与问题规模大小相关。     

卫星编队飞行的地球扁率摄动分析

本文研究了地球扁率J2项摄动对卫星编队飞行的影响。首先，给出了编队飞行数学描述，推导了轨道根数和相对运动状态的关系式；然后，将卫星编队的受摄影响分解为整体摄动和相对摄动，分别得到了解析解，重点分析了相对摄动规律。研究结果对卫星编队的设计有一定的参考价值。     

深空机动对运载火箭发射火星探测轨道研究

为解决长征(LM)运载火箭发射火星探测器转移轨道时,因低温入轨级最长允许滑行时间及测控限制,有效发射日期窗口亟需拓展的问题,采用主矢量理论结合序列二次规划算法(SQP),研究了探测器深空机动(DSM)对优化运载火箭发射火星转移轨道的作用。在发射直接转移火星探测轨道算法基础上,重点研究了包含引力影响球(SOI)内近地及近火飞行段后,采用主矢量获取深空机动最优猜测初值的分析算法,通过直接使用探测器近火点目标轨道参数优化运载火箭发射轨道,研究对比不同优化目标及设计约束下深空机动的分析结果,证实深空机动对降低转移轨道总发射能量需求、拓展发射日期窗口的高效性;该算法已应用于工程设计。     

The mitigation, management, and survivability of asteroid/comet impact with Earth

The chances that Earth will collide with a significant near earth object (NEO) within the next century are very small, but such a collision is possible, would be catastrophic, and could happen at any time. Much discussion has been devoted to methods of diverting these objects away from Earth through the use of space technology. However, if these efforts are unsuccessful, we would need to implement effective strategies to survive the event, no matter how cataclysmic. To date, disaster management for various impact scenarios has not been addressed (except in novels and Hollywood films). An impact disaster may be many orders of magnitude greater than any disaster the human species has ever experienced. Initially, technology and experience gained in other large-scale disasters will most likely form the foundation of how these impact events will be managed and classified. Given the size and energy of the projectile, the estimated area of damage, and whether impact effects might be localized or global in nature, we can begin to build basic disaster response scenarios, anticipate public health concerns, and formulate questions in need of answers. Questions we must deal with include: what will be required technologically, sociologically, and medically to survive? What types of evacuation plans and warning systems might be required? Capabilities in need of further investigation include: technological protection strategies related to ‘impact winter’, expanded chemical hazard control methodologies, food storage and production, roles of national governments, and international cooperation. Whatever the magnitude and severity of the event, we must reflect on what we know, what capabilities we can apply, develop or adapt, and seriously investigate what might be done to manage it and survive.     

嫦娥五号探测器多圈调相地月转移应急轨道设计与分析

针对嫦娥五号任务上升段末期火箭二级发动机可能出现的提前关机故障造成入轨半长轴偏差较大和中途修正速度增量超限问题,提出了多圈调相地月转移轨道应急控制策略.首先,分析了不同入轨半长轴偏差、中途修正时刻与中途修正速度增量消耗之间的关系;其次,针对半长轴偏差较大问题,基于微分改正算法与B平面参数,设计了解析窗口搜索与多圈调相地...     

Improving dUT1 from VLBI intensive sessions with GRAD gradients and ray-traced delays

Exact knowledge of the angle of Earth rotation UT1 with respect to coordinated time UTC, dUT1, is essential for all space geodetic techniques. The only technique which is capable of determining dUT1 is Very Long Baseline Interferometry (VLBI). So-called Intensive VLBI sessions are performed on a daily basis in order to provide dUT1. Due to the reduced geometry of Intensive sessions, there is however no possibility to estimate tropospheric gradients from the observations, which limits the accuracy of the resulting dUT1 significantly. This paper deals with introducing the information on azimuthal asymmetry from external sources, thus attempting to improve the dUT1 estimates. We use the discrete horizontal gradients GRAD and the empirical horizontal gradients GPT3 as well as ray-traced delays from the VieVS ray-tracer for this purpose, which can all be downloaded from the VMF server of TU Wien (http://vmf.geo.tuwien.ac.at). The results show that this strategy indeed improves the dUT1 estimates when compared to reference values from multi-station VLBI stations, namely by up to 15%. When converted to length-of-day (LOD), the estimates can be compared to LODs from global analyses of Global Navigation Satellite Systems (GNSS). Here, the improvement amounts to up to 7% compared to neglecting a priori information on azimuthal asymmetry.     

HOI延迟对LEO卫星简化动力学POD的影响

通常使用无电离层(IF)线性组合(LC)消除低地球轨道(LEO)卫星简化动力学精密定轨(POD)一阶电离层延迟误差,忽略了高阶电离层(HOI)延迟误差。随着LEO卫星POD技术的发展,计算不同轨道高度的HOI延迟并探索其变化已成为进一步提高POD精度的重要手段。首先,使用国际参考电离层-2016(IRI-2016)和国际地磁参考场第13代(IGRF-13)模型,计算电离层穿刺点(IPP)位置和地磁场强度。其次,使用平滑星载GNSS数据计算电离层斜路径总电子含量(STEC)。然后,分别计算GOCE、GRACE-A和SWARM-A/B卫星的二阶和三阶电离层延迟。最后,评估了HOI延迟对LEO卫星重叠轨道分析、卫星激光测距(SLR)检核和精密科学轨道(PSO)比较结果的影响。实验结果表明：HOI延迟对LEO卫星简化动力学POD的影响大约在毫米至厘米的数量级上;HOI延迟对LEO卫星简化动力学POD外符合精度的影响分别达到0.92,0.22,0.21和0.18 mm;随着LEO卫星轨道高度的增加,HOI延迟对LEO卫星简化动力学POD的影响减小。     

Earth Observation Technologies for Sustainable Development

The multi-platform, multi-band and multi-mode Earth Observation (EO) system has been established in China in recent years. The advanced technologies are playing more and more important role for sustainable development in whole country. This paper introduces the results and achievements of EO monitoring for agriculture, EO surveying for land resources, EO monitoring for ecological environment, EO support for national surveying and national e-government, natural disaster monitoring and emergency response. It points out that the EO technologies could contribute more to the country, including in the field of global change in the coming decade.