中低轨道卫星控制方法

针对中低轨道卫星，对平面内卫星半长轴α、偏心率e和近地点幅角w联合调整，以及平面外轨道倾角调整等进行了理论推导.用α，e，w联合修正法对初始轨道捕获、轨道保持和轨道倾角调整进行的仿真实验结果表明，用α，e，w同时修正可实现高精度的平面内轨道调整。另外，平面外倾角调整应尽可能在近地点和远地点完成，以使对升交点赤经的影响最小。     

太阳同步回归轨道的长期演变与控制

近地轨道的遥感卫星绝大部分都采用太阳同步回归轨道。这类轨道由于受到大气阻力的影响,半长轴将不断地衰变并导致地面轨迹的东漂,为保持回归特性需周期性地对半长轴进行调整。另一类长期变化是太阳引力引起的倾角变化,这是太阳同步轨道特有的。倾角长期的变化又进一步导致回归轨道的标称半长轴和降交点地方时的相应变化。文章给出了这些变化的解析模型以及轨道控制的策略。     

基于迭代修正方法的严格回归轨道设计

通过分析太阳同步回归轨道的轨道根数和星下点经度/纬度的关系,推导了一组轨道根数的修正公式。基于高精度轨道动力学模型和升交点位置确定方法,构造了关于轨道半长轴和轨道倾角的迭代修正方法。针对偏心率矢量的动力学系统所具有的极限环特性,构造了平均法求其解析近似,从而实现冻结轨道特性对偏心率和近地点幅角的迭代修正。结合迭代修正,得到一组严格回归的轨道根数。该轨道能够重访空间目标点,具有较高的回归精度。     

倾角偏置太阳同步轨道的地面轨迹保持方法

为在倾角偏置条件下保持太阳同步轨道卫星的地面轨迹,在考虑地球扁率摄动、大气阻力摄动和太阳引力谐振等主要影响因素,以及卫星地面轨迹允许漂移范围的基础上,采用主动超调与被动控制结合的策略,提出了一种初始半长轴偏置后的卫星地面轨迹保持方法。分析了半长轴和倾角摄动变化率,以及初始半长轴和倾角偏置量对地面轨迹漂移的影响。仿真结果表明,该法可基本满足设计阶段的精度要求。     

载人飞船自动化轨道设计方法研究

为提高戢人飞船轨道设计的自动化程度和快速性,对自动化轨道设计方法进行了研究.分析了裁人飞船不同阶段飞行轨道的约束条件,用约束条件首先确定了轨道的半长轴取值范围,由回归条件可确定回归圈数的取值范围;在给定的回归和返回条件下,迭代求解运行轨道的轨道半长轴与倾角;根据运行轨道设计结果,反推初始轨道和留轨轨道的轨道根数.自动化...     

FY-2C星发射轨道计算与分析

根据卫星发射窗口的一般性和风云二号(FY-2)C气象卫星特定限制条件,计算了2004年10月19日符合要求的发射窗口.在比较上午和晚上发射窗口的基础上,确定C星选择上午发射窗口.给出了影响卫星定点捕获所需速度增量的入轨轨道参数和点火姿态等因素,并仿真计算了轨道半长轴、近地点高度、倾角和近地点幅角与速度增量的关系.分析结果表明,卫星发射窗口的确定与星、地、日间的位置密切相关.入轨偏差越小,定点捕获所需肼燃料消耗也越少.     

多冲量轨道交会问题算法研究

针对平面内轨道交会问题给出了一种多冲量轨道控制算法,其融合了半长轴、偏心率、近地点幅角联合控制方法和轨道相位捕获控制方法。首先建立了等点火时长计算模型和理论起控时刻计算模型,在此基础上设计了控制序列自动调整算法。基于该算法,在给定测控条件、单次控制最大点火时长等约束条件下,可快速求解实现与目标航天器轨道交会的多冲量控制策略。最后,通过轨道交会问题算例,验证了算法的有效性。该方法可应用于轨迹捕获、航天器组网控制、航天器交会远程导引等航天场景。     

GEO卫星弃置轨道稳定性分析及离轨策略优化

运用解析和数值计算两种方法,分析了各种摄动源对地球静止轨道(GEO)卫星弃置轨道近地点高度变化的影响,得到了近地点高度的变化规律。利用二阶日月引力摄动可造成GEO卫星弃置轨道近地点升高的特点,提出新的卫星离轨策略,在不满足机构间空间碎片协调委员会(IADC)"空间碎片减缓指南"中,GEO卫星弃置轨道偏心率小于0.003要求的情况下,还可以保证卫星不再进入GEO保护区域。     

SDEEM2015空间碎片环境工程模型

文章介绍了哈尔滨工业大学空间碎片高速撞击研究中心"十二五"期间发布的空间碎片环境工程模型(SDEEM 2015)。该模型可实现LEO空间碎片环境描述,空间碎片撞击风险评估以及地基探测结果仿真,还可输出LEO航天器不同轨道位置处空间碎片撞击通量随撞击方位角、撞击速度及碎片尺寸的分布规律,地基探测设备探测区域内空间碎片空间密度及通量的分布情况等信息。SDEEM 2015适用轨道高度范围为200~2000 km,时间范围为1959年—2050年,所考虑的空间碎片来源包括解体碎片、Na K液滴、固体火箭发动机喷射物、溅射物和剥落物。     

大椭圆轨道气动变轨与轨道部署

提出了一种服务飞行器的大椭圆轨道气动变轨方案.根据速度轨道最优参数确定气动变轨动力学方程及参数,计算了变轨第一、二阶段的能力.研究了轨道部署方案,讨论了大椭圆轨道近地点幅角与轨道倾角,以及待机轨道覆盖性能.研究表明:3个空间飞行器就可100%覆盖低轨道主要目标群.     

Perturbation effect of the Coulomb drag on the orbital elements of the earth satellite moving in the ionosphere

The perturbation effects of the Coulomb drag on the orbital elements of the earth satellite moving in the ionosphere are studied. The theoretical results show that the Coulomb drag results in both the secular and periodic variation in the semi-major axis and eccentricity. However, the argument of the perigee exhibits no secular variation, but only periodic variation. The inclination and the ascending node remain no variation. As an example, the secular effects of the Coulomb drag on the semi-major axis and the eccentricity of an ionosphere satellite Alouette (S-27) are calculated in the ionosphere with the mean height 1000 km. It can be shown that the semi-major axis contracts and the eccentricity decreases for the case of the Coulomb drag under the interaction of the ions with the electric field of an earth satellite.     

Density and mass distributions of orbital debris

Area-to-mass ratios for orbital debris tracked by the U.S. Space Command were calculated from observed changes in apogee and perigee altitude due to atmospheric drag. The area-to-masses observed for the orbital debris were similar to those found for debris from laboratory breakups, and suggest that much of the debris is composed of crumpled thin plates or of insulation material with low effective density. Areas for the debris objects were derived from radar cross-section data. Object masses were calculated from the ratio of the RCS-derived area to the area-to-mass ratio. Analysis of the distributions of fragment masses from the breakups suggests that in many cases, only a portion of the initial object breaks up into small fragments.     

定时定点月面着陆全程轨道控制设计

针对定时定点月面着陆的目标要求，提出了全程轨道控制设计方法。进行了包括地月转移、近月制动、环月降轨和动力下降的全程轨道控制的分段设计和联合规划，实现在入轨轨道偏差条件下的定时定点月面着陆。分别构建了中途修正、近月制动、环月降轨三段轨道控制的规划变量和目标参数；根据轨道倾角建立了动力下降点与着陆点的匹配转换关系。设计了中途修正、近月制动、环月降轨、动力下降的全程轨道控制策略的联合规划。建立了着陆位置偏差与轨道倾角偏差、着陆时间偏差与轨道半长轴偏差的修正关系，修正设计了中途修正目标倾角和近月制动目标半长轴。仿真算例表明，在入轨偏差轨道条件下，保证了中途修正后的飞行轨道与标称轨道基本一致，实现了与标称状态基本一致的定时定点月面着陆。可应用于月球着陆、月球采样返回以及载人登月等实施月面定时定点着陆任务的轨道设计和控制实施。     

Assessing the Risk of Orbital Debris Impact

A Space Debris Impact Risk Analysis Tool (SDIRAT) was developed and implemented to assess the orbital debris impact risk on a specified target in Earth orbit, in terms of flux, relative velocity, impact velocity, direction of the incoming particles, debris mass and diameter. Based on a deterministic approach, SDIRAT uses a realistic orbital debris population where each representative particle is identified by its rectangular coordinates (position and velocity) at a reference epoch. Using this information, some geometrical algorithms were developed and implemented to evaluate the contribution of each particle to the incoming flux. The position of the particle with respect to a specified target drives the selection criteria to reject, or select, it as a possible projectile. On the other hand, the relative velocity vector can be used to estimate the impact direction of the incoming flux. SDIRAT was conceived as a general tool for a variety of scenarios, such as low circular and elliptical orbits, up to the geosynchronous ring. This paper presents some examples of possible applications, including the computation of the incoming debris flux on SAX (low Earth orbit), SIRIO (geosynchronous orbit) and the IRIS upper stage (elliptical orbit). Other applications assess the impact risk for the Soviet Radar Ocean Reconnaissance Satellites Cosmos 1900 and Cosmos 1932.     

Continuum Model for Space Debris Evolution with Account of Collisions and Orbital Breakups

The paper discusses the mathematical modeling of long-term orbital debris evolution taking into account mutual collisions of space debris particles of different sizes. Investigations and long-term forecasts of orbital debris environment evolution in low Earth orbits are essential for future space mission hazard evaluation and for adopting rational space policies and mitigation measures. The paper introduces a new approach to space debris evolution mathematical modeling based on continuum mechanics incorporating partial differential equations. This is an alternative to the traditional approaches of celestial mechanics incorporating ordinary differential equations to model fragments evolution. The continuum approach to orbital debris evolution modeling has essential advantages for describing the evolution of a large number of particles, because it replaces the traditional tracking of space objects by modeling the evolution of their density of distribution.     

Additional historical solid rocket motor burns

The use of orbital solid rocket motors (SRM) is responsible for the release of a high number of slag and Al₂O₃ dust particles which contribute to the space debris environment. This contribution has been modeled for the ESA space debris model MASTER (Meteoroid and Space Debris Terrestrial Environment Reference). The current model version, MASTER-2005, is based on the simulation of 1076 orbital SRM firings which mainly contributed to the long-term debris environment. SRM firings on very low earth orbits which produce only short living particles are not considered. A comparison of the modeled flux with impact data from returned surfaces shows that the shape and quantity of the modeled SRM dust distribution matches that of recent Hubble Space Telescope (HST) solar array measurements very well. However, the absolute flux level for dust is under-predicted for some of the analyzed Long Duration Exposure Facility (LDEF) surfaces. This indicates that some past SRM firings are not included in the current event database. Thus it is necessary to investigate, if additional historical SRM burns, like the retro-burn of low orbiting re-entry capsules, may be responsible for these dust impacts. The most suitable candidates for these firings are the large number of SRM retro-burns of return capsules. This paper focuses on the SRM retro-burns of Russian photoreconnaissance satellites, which were used in high numbers during the time of the LDEF mission. It is discussed which types of satellites and motors may have been responsible for this historical contribution. Altogether, 870 additional SRM retro-burns have been identified. An important task is the identification of such missions to complete the current event data base. Different types of motors have been used to de-orbit both large satellites and small film return capsules. The results of simulation runs are presented.     

USA-193 decay predictions using public domain trajectory data and assessment of the post-intercept orbital debris cloud

In early 2008, the need arose to predict the orbital decay of the American spacecraft USA-193, whose characteristics, function and orbit were classified information. With no orbit data and independent Italian tracking capability available, we turned our attention on the orbits determined by a worldwide network of about 20 visual satellite observers. The orbits of USA-193 obtained from their visual observations were therefore used as the sole source of orbit information. Contrary to our expectations, this exercise was extremely successful and we learned a lot in the process. The orbits provided by the visual observers were very accurate for such a low satellite (although the minimum and very stable level of solar activity helped considerably); however, data gaps of a few days were sometimes possible, due to unfavorable pass geometry or weather and light conditions. In any case, the orbital period and the semimajor axis were so accurate that it was possible for us to obtain very good decay fits using special perturbation software, including various atmospheric density models together with all the other relevant perturbing accelerations. We were therefore able to estimate accurate values of the ballistic parameter and the resulting decay and reentry predictions were extremely stable. Amateur optical observations and images of USA-193 had also led to a rough estimation of the shape and sizes of the satellite, revealing that the solar arrays had never been deployed. With this information, and taking into account our estimates of the ballistic parameter, we obtained reasonable and consistent values of the spacecraft mass. Based on previous reentry fragmentation analyses, we were then able to guess the expected USA-193 casualty area, casualty expectancy, debris ground footprint and probability of impact in Italy. Lastly, after the decision by the US Government to destroy the satellite, we independently predicted the interception time windows and the post-event ground tracks. Following the successful spacecraft breakup, we analyzed the evolution of the resulting debris cloud and assessed its (very limited) adverse impact on the circumterrestrial environment.     

The Investigation of Possible Approaches of Cataloged Space Objects to Manned Spacecraft

Initial orbital parameter errors are used to examine the miss distance between a spacecraft and an ensemble of tracked objects by a Monte Carlo-type analysis. The radial separation between orbits is evaluated and a keep-out zone is determined, which reduces the risk of collision to an acceptable level.An operational prediction methodology is suggested based on a catalog database, which identifies potentially hazardous approaches and computes the probability of collision for selected spacecraft. An example for the Mir Space Station is presented, which estimates the collision probability and the cross-sectional flux of cataloged objects for the time frame of interest. The results appear to be in good agreement with those of other space debris models.