超低轨卫星气动力辅助轨道控制研究

针对超低轨卫星所受气动力显著的特点,提出一种利用气动舵的气动力辅助轨道控制方法。通过分析大气旋转、卫星所处空间位置以及气动舵偏转角度对气动力的影响,对提出的轨道控制方法进行了优化。该方法通过调整气动舵产生连续微小的气动力对卫星轨道进行控制,使各轨道要素均保持在误差容限范围内。将其应用于太阳同步轨道上的对地观测卫星,仿真结果表明,该方法可以在卫星姿态保持三轴对地稳定的前提下,实现轨道保持控制,保证任意纬度下卫星实际位置与标称轨道位置偏差在给定范围内。     

SST-LL重力测量卫星轨道分析

论述了SST-LL重力测量卫星科学任务对轨道寿命、地面覆盖性能、轨道高度单圈波动、星间距离变化范围的需求。根据需求,计算了轨道的自然衰减情况,得出轨道初始高度为500km;综合考虑地面覆盖要求及运载火箭能力,得出了最佳轨道倾角为89°;得出了0.002 0偏心率下轨道高度波动范围不超过50km;分析得出星间距离的长周期变化主要受大气阻力影响,初步确定了轨道控制方案,即定期对受大气阻力较大的卫星进行轨道机动。     

Stochastic control of pitch motion of satellites using stabilizing flaps

The modelling, analysis and synthesis of an attitude control system for low orbit artificial satellites using stabilizing flaps are presented. The function of the system is to maintain the satellite aligned with the local vertical. The aerodynamic forces on the satellite are modelled assuming free molecular flow using the kinetic theory of gases. The control system development is considered through the application of stochastic control concepts. The satellite motion is described by the equations of motion based on Newtonian formulation. Starting from the separation principle, a sequential procedure is developed in which the state estimation and control problems are handled simultaneously. State estimate is provided by Kalman filter using the information about the position of the satellite and of the flaps. The controller acts on satellite in real time, and the stabilizing flaps are the only control elements.     

基于受摄轨道模型的小卫星轨道摄动分析研究

小卫星在实际运行中受到多种摄动力的作用,这会对其轨道造成不同程度的影响,因此在小卫星的轨道设计与控制中,摄动是必须考虑的重要因素。本文以500km高的小卫星太阳同步轨道为研究对象,运用轨道摄动的基本理论,估计了地球非球形引力、大气阻力、太阳光压及第三体引力的量级并进行比较;建立小卫星轨道摄动分析模型,并在此模型的基础上,利用计算机仿真技术,对小卫星轨道摄动问题展开仿真研究,验证了几种主要摄动力的量级估计的结果,分析比较了几种主要摄动力对小卫星运行轨道的影响程度及规律,本文结果对小卫星轨道设计与控制具有很好的参考价值。     

星载电场探测仪的传感器空间布局研究

电场探测仪是卫星进行高精度电场探测的关键载荷,其传感器的空间布局对探测精度影响很大。文章对传感器空间布局的影响因素和分析方法进行了研究,并以轨道高度500km的太阳同步轨道卫星为例,结合卫星的实际任务运行,对虚假光电场控制、电场探测仪传感器的几何布局构型、传感器与卫星的相互遮挡和干涉关系进行了分析,并最终优化确定了传感器的空间布局。研究结果表明,优化的传感器空间布局可以在设计阶段就针对多种误差,有效地提高其探测精度。     

分离模块异构航天器集群松散队形设计

针对近地轨道分离模块航天器集群,考虑航天器之间面质比差异,提出一种能在较长时间内维持两星之间相对距离的松散队形设计方法。该方法以相对偏心率向量和相对轨道倾角向量描述松散队形,以两颗卫星之间的轨道长半轴之差和相对相位角之差为优化变量,并且通过设置虚拟空间圆解决避碰问题,保证在考虑气动力摄动的情况下,异构航天器松散编队能够有较长时间满足距离要求。仿真研究表明,针对轨道高度为500 km的参考轨道,当两星面质比分别为0.003 m 2/kg和0.0032 m 2/kg时,两颗卫星之间的距离能够在50天内处于200 m到20 km之间。     

Biaxial Mode of Rotation of a Satellite in the Orbit Plane

A mode of motion of a satellite with respect to its center of mass is studied, which is called the biaxial rotation in the orbit plane. In this mode of rotation, an elongated and nearly dynamically symmetric satellite rotates around the longitudinal axis, which, in turn, rotates around the normal to the plane of an orbit; the angular velocity of rotation around the longitudinal axis is several times larger than the orbital angular velocity, deviations of this axis from the orbit plane are small. Such a rotation is convenient in the case when it is required to secure a sufficiently uniform illumination of the satellite's surface by the Sun at a comparatively small angular velocity of the satellite. The investigation consists of the numerical integration of equations of the satellite's motion, which take into account gravitational and restoring aerodynamic moments, as well as the evolution of the orbit. At high orbits, the mode of the biaxial rotation is conserved for an appreciable length of time, and at low orbits it is destroyed due to the impact of the aerodynamic moment. The orbit altitudes and the method of constructing the initial conditions of motion that guarantee a sufficiently prolonged period of existence of this mode are specified.     

Electron flux variations at altitudes of 600–800 km in the second half of 2014. preliminary results of an experiment using RELEC equipment onboard the satellite <Emphasis Type="Italic">VERNOV</Emphasis>

The results of measurements of fluxes and spectra carried out using the RELEC (relativistic electrons) equipment onboard the VERNOV satellite in the second half of 2014 are presented. The VERNOV satellite was launched on July 8, 2014 in a sun-synchronous orbit with an altitude from 640 to 830 km and an inclination of 98.4°. Scientific information from the satellite was first received on July 20, 2014. The comparative analysis of electron fluxes using data from RELEC and using experimental data on the electron detection by satellites Elektro-L (positioned at a geostationary orbit) and Meteor-M no. 2 (positioned at a circular polar orbit at an altitude of about 800 km as the VERNOV satellite) will make it possible to study the spatial distribution pattern of energetic electrons in near-Earth space in more detail.     

On the Accuracy of the Conjugation of High-Orbit Satellites with Small-Scale Regions in the Ionosphere

The degree of uncertainty that arises when mapping high-orbit satellites of the Cluster type into the ionosphere using three geomagnetic field models (T89, T98, and T01) has been estimated. Studies have shown that uncertainty is minimal in situations when a satellite in the daytime is above the equatorial plane of the magnetosphere at the distance of no more than 5 R_E from the Earth’s surface and is projected into the ionosphere of the northern hemisphere. In this case, the dimensions of the uncertainty region are about 50 km, and the arbitrariness of the choice of the model for projecting does not play a decisive role in organizing satellite support based on optical observations when studying such large-scale phenomena as, e.g., WTS, as well as heating experiments at the EISCAT heating facility for the artificial modification of the ionosphere and the generation of artificial fluctuations in the VLF band. In all other cases, the uncertainty in determining the position of the base of the field line on which the satellite is located is large, and additional information is required to correctly compare the satellite with the object in the ionosphere.     

Optical effects of the operation of the onboard engine of the <Emphasis Type="Italic">Progress M-17M</Emphasis> spacecraft at thermospheric heights

This paper presents the results of optical observations in the active space experiment “Radar-Progress” on April 17, 2013, after switching on the approach-correction engine of the Progress M-17M cargo spacecraft at thermospheric heights (412 km), are presented in this paper. During engine operation, a region of enhanced emission intensity has been recorded. It was presumably related to the scatter of twilight solar emission at the engine exhausts in the cargo spacecraft orbit and, probably to the occurrence of an additional emission in the atomic oxygen line [OI] 630 nm. The maximum observed dimensions of the emission region were ~350 and ~250 km along the orbit and across it, respectively. The velocity of the expansion of the emission region at the first moments after the initiation of engine operation was ~7 and ~3.5 km/s along the orbit and across it, respectively. The maximum intensity of the disturbed region is estimated to be a value equivalent to ~40–60 R within the spectral band of 2 nm. No optical manifestation, which would exceed the natural variations in brightness of the night airglow and which would be related to possible large-scale modification of the ionosphere, was detected in the natural emission lines [O] 557.7 and 630.0 nm in a zone remote from the place of injection of engine exhausts.     

电动绳系在低极轨卫星中的应用研究

低极轨卫星具有轨道周期短、对地观测分辨率高等优点,但由于所在轨道大气阻力大,其使用寿命受到较大限制。文章提出采用水平结构电动绳系抵消低极轨卫星大气阻力的方法,通过系绳电流与地球磁场相互作用产生洛仑兹力进行推进,进而在无燃料消耗的情况下实现对低极轨卫星轨道高度的维持。初步分析了该方法在低极轨不同尺寸卫星中的应用潜力,计算了160 、400 和800 km 典型高度低极轨卫星所经历的地球磁场、电离层和高层大气环境相关参数变化,比较了不同条件下电动绳系推力与大气阻力大小随轨道位置的变化。分析结果表明,该方法适用于400 km 轨道高度以上大卫星;在满足一定系绳长度和轨道高度的条件下,电动绳系可以有效延长低极轨卫星的轨道寿命。     

第二类无奇点根数的北斗历书参数设计

为统一北斗三类卫星的历书拟合算法,提出基于第二类无奇点根数进行历书参数设计的方法,设计了以倾角向量变率作为摄动参数的历书参数模型,并给出新的历书模型的用户使用算法。利用覆盖2013年全年的实际在轨卫星的数值轨道进行了历书拟合试验。结果表明,地球静止轨道（GEO）和倾斜地球同步轨道（IGSO)卫星的拟合位置误差为2~4km,拟合用户距离误差（URE）约为1km,中圆地球轨道（MEO）卫星的拟合位置误差为1~2km,拟合URE约为500m。通过分析6个轨道根数和2个摄动参数全年的变化范围,对新历书模型进行量化单位和占用比特位的通信接口设计,定量分析量化单位对历书表达精度的影响。结果表明,参数截断后对位置误差的影响小于50m,对URE误差的影响小于5m。因此,历书量化误差对信号捕获以及首次定位时间带来的影响可以忽略不计。     

Realization of modes of satellite attitude motion with a small level of microaccelerations using electromechanical executive devices

Quasi-static microaccelerations are estimated for a satellite specially designed to perform space experiments in the field of microgravity. Three modes of attitude motion of the spacecraft are considered: passive gravitational orientation, orbital orientation, and semi-passive gravitational orientation. In these modes the lengthwise axis of the satellite is directed along the local vertical, while solar arrays lie in the orbit plane. The second and third modes are maintained using electromechanical executive devices: flywheel engines or gyrodynes. Estimations of residual microaccelerations are performed with the help of mathematical modeling of satellite’s attitude motion under the action of gravitational and aerodynamic moments, as well as the moment produced by the gyro system. It is demonstrated that all modes ensure rather low level of quasi-static microaccelerations on the satellite and provide for a fairly narrow region of variation for the vector of residual microacceleration. The semi-passive gravitational orientation ensures also a limited proper angular momentum of the gyro system.     

超低轨航天器气动力分析与减阻设计

轨道降低,航天器受到的气动力增大,气动力对航天器影响显著。考虑自由分子流态 下的超低轨航天器,利用分割法把简单外形的航天器分割为几部分,分别计算各部分的气动 力,然后相加获得总的气动力效果;通过对平面的气动力进行计算分析,提出了超低 轨航天器的减阻设计方法;结果表明：当轨道高度降低到250 km左右时,航天器受到的气动 阻力比500 km高出约2个数量级;一般情况下,超低轨航天器应采用细长体构型,减小迎风 面积;侧面积引起的航天器阻力已经不可忽略,应采用侧面光滑技术,减少侧面阻力;当超 低轨航天器长细比超过一定限度后,随着长细比增大,大气阻力升高。
     

低轨星座对静止轨道卫星同频干扰指标研究

随着全球低轨星座系统的快速部署及应用,非静止轨道卫星对静止轨道卫星系统的同频干扰问题日益凸显。为保护静止轨道卫星系统不受有害干扰,国际电联现行无线电规则中规定了非静止轨道卫星系统应满足的等效功率通量密度限值或干扰噪声比限值,但所适用频段及限值标准仍在不断修订完善中。为了精确定量评估低轨星座对静止轨道卫星的同频干扰,通过对等效功率通量密度限值和干扰噪声比限值的确定方法及演进历程进行研究,分析了上述限值与静止轨道卫星实际被干扰的对应关系,并以典型倾斜轨道星座和极地轨道星座为例,分析了不同干扰指标对卫星系统间干扰判定结果的影响,当静止轨道卫星系统的实际被干扰门限低于国际电联制定等效功率通量密度限值选用的参考门限时,建议低轨星座选择干扰噪声比限值作为开展频率干扰分析与判定的依据。     

带有控制增益自校正的甚低轨道卫星自主轨道维持方法

为实现甚低轨道的长期稳定运行,分析了甚低轨道的摄动特性,设计了一种带有轨控增益校正的自主轨道维持方法。该方法可通过前一次轨控的结果对轨控增益进行校正,提高轨控算法对卫星质量、推力大小等不确定因素的鲁棒性,逐渐提高轨道控制的精度。对轨道控制的频率、每次轨控的时间长度及对偏心率的影响进行了分析,仿真结果表明:自主轨道维持方法能实现甚低轨道高度维持控制,在参数不确定的情况下,与传统算法相比可大幅提高轨道控制的精度,确保平均偏心率矢量收敛,满足甚低轨道卫星的长寿命要求。所设计的算法结构简单,运算量小,可由目前的星载计算机实现。     

Modeling of the aerodynamic moment acting upon a satellite

We consider the issues of modeling the moments of aerodynamic forces acting upon a satellite with gravitational system of stabilization. It is assumed that satellite orbits are almost circular with heights in the range 550–750 km. Simplified analytical expressions are suggested for the aerodynamic moment in the case when a satellite moves in the regime of gravitational orientation. Accuracy of the obtained expressions is estimated to be compared with that of expressions derived under the assumption of constant coefficient of frontal resistance. An analysis is made of short-periodic variations of the atmosphere density occurring due to orbital motion of a satellite. It is demonstrated that these variations can result in a substantial change of the aerodynamic moment, and their approximation by a truncated Fourier series is suggested. Estimates of the accuracy of the suggested approximation are given.     

吸气式电推进中的气体捕集系统的设计分析

针对吸气式电推进系统中的气体捕集系统,提出了一种能够准确计算气体捕集率的理论模型,并以此为基础开展了气体捕集系统的优化设计.首先,通过分析几类代表性气体捕集系统的捕集特点,提取了影响气体捕集率的关键参数.然后,通过分析进气道内气体分子的微观行为,推导得到了气体捕集率的理论公式,获得了无量纲管长、末端净透射率等关键参数对...     

Dynamics of the orbital cable system

The Orbital Cable System (OCS) consists of a vehicle with an engine, a long connecting cable (string) and a satellite probe for low altitude geophysical explorations. The vehicle orbits the Earth at an altitude of 200–250 km and tows a probe at an altitude of 100–150 km. The air drag is compensated by the vehicle engine thrust. In the OCS dynamics study the cable weight, elasticity and air drag are taken into account. The OCS stationary motions are found, and stability of these motions is investigated. The OCS periodical motions that are close to the stationary motions are found. Simple ways of the OCS deployment in orbit are described.     

The Brazilian scientific microsatellite SACI-1

The National Space Research Institute (INPE) is developing the first Brazilian Scientific Microsatellite (SACI-1) based on the vanguard technology and on the experience acquired through projects developed by Brazilian Space Program. The SACI-1 is a 750km polar orbit satellite. The spacecraft will combine spin stabilization with geomagnetic control and has a total mass of 60 kg. The overall dimensions are 640×470×470 mm. The SACI-1 satellite shall be launched together with CBERS (China-Brazil Earth Resource Satellite). Its platform is being designed for multiple mission applications. The Brazilian Academy of Sciences has selected four scientific payloads that characterize the mission. The scientific experiments are: ORCAS (Solar and Anomalous Cosmic Rays Observation in the Magnetosphere), PLASMEX (Study of Plasma Bubbles), FOTSAT (Airglow Photometer), and MAGNEX (Geomagnetic Experiment).