GYRO BIAS ON-ORBIT CALIBRATION FOR MICRO SATELLITES

According to gyro application in micro-satellites, a new gyro bias real-time on-orbit calibration technology is presented and it is independent of any other sensors. The approach relies on gyro on-orbit measurements restricted by satellite attitude dynamics and estimates the gyro bias generated when the gyro is electrified. Observability of the calibration model is analyzed and applicable conditions of the technology are derived. Simulation results indicate that the calibration algorithm is accurate and robust at gyro sampling rate, and its convergence speed is fast. Within the given attitude dynamics model error, the convergence time is less than 100 s and the convergence accuracy is about 1.0 （°）/h. Calibration performance can meet requirements of spacecraft operations.

On-orbit target tracking and inspection by satellite formation

A new type of estimator is developed for the satellite formation to track and inspect on-orbit targets. The follower satellite in the formation works without relative sensors, and its target pointing commands are derived based on relative orbital dynamics. The centralized estimator based on truth measurement is designed, however, this estimator is proved unstable because of the lack of necessary measurement information. After that, an alternative estimator based on pseudo measurement is designed, and its observability and controllability are analyzed to qualitatively evaluate the convergence performance. Finally, an on-orbit target inspection scenario is numerically simulated to verify the performance of the estimator based on pseudo measurement.

On-orbit Geometric Calibration of Linear Push-broom Optical Satellite Based on Sparse GCPs

The paper presents a geometric calibration method based on the sparse ground control points (GCPs), aiming to the linear push-broom optical satellite. This method can achieve the optimal estimate of internal and external parameters with two overlapped image pair along the charge-coupled device (CCD), and sparse GCPs in the image region, further get rid of the dependence on the expensive calibration site data. With the calibrated parameters, the line of sight (LOS) of all CCD detectors can be recovered. This paper firstly establishes the rigorous imaging model of linear push-broom optical satellite based on its imaging mechanism. And then the calibration model is constructed by improving the internal sensor model with a viewing-angle model after an analysis on systematic errors existing in the imaging model is performed. A step-wise solution is applied aiming to the optimal estimate of external and internal parameters. At last, we conduct a set of experiments on the ZY-3 NAD camera and verify the accuracy and effectiveness of the presented method by comparison.

On-orbit Geometric Calibration and Preliminary Accuracy Evaluation of GF-14 Satellite

GF-14 satellite is a new generation of sub-meter stereo surveying and mapping satellite in China,carrying dual-line array stereo mapping cameras to achieve 1∶10000 scale topographic mapping without Ground Control Points(GCPs).In fact,space-based high-precision mapping without GCPs is a challenging task that depends on the close cooperation of several payloads and links,of which on-orbit geometric calibration is one of the most critical links.In this paper,the on-orbit geometric calibration of the dual-line array cameras of GF-14 satellite was performed using the control points collected in the high-precision digital calibration field,and the calibration parameters of the dual-line array cameras were solved as a whole by alternate iterations of forward and backward intersection.On this basis,the location accuracy of the stereo images using the calibration parameters was preliminarily evaluated by using several test fields around the world.The evaluation result shows that the direct forward intersection accuracy of GF-14 satellite images without GCPs after on-orbit geometric calibration reaches 2.34 meters(RMS)in plane and 1.97 meters(RMS)in elevation.

Retrieval strategy for failed satellite on tether’s optimal balance swing angle

A retrieval control strategy for failed satellite,which is connected to a servicing spacecraft by a tether,is studied.The Lagrange analytical mechanics based dynamics modeling for the system composed of a servicing spacecraft,a tether and a failed satellite,is presented under the earth center inertia coordinate system,then model simplification is conducted under the assumption that the failed satellite’s mass is far smaller than the servicing spacecraft’s,meanwhile the tether’s length is far smaller than the size of the servicing spacecraft’s orbit.Analysis shows that the retrieval process is intrinsically unstable as the Coriolis force functions is a negative damping.A retrieval strategy based on only the tether’s tension is designed,resulting in the fastest retrieval speed.In the proposed strategy,firstly,the tether’s swing angle amplitude is adjusted to 45?by deploying/retrieving the tether;then the tether swings freely with fixed length until it reaches negative maximum angle–45?;finally,the tether is retrieved by the pre-assigned exponential law.For simplicity,only the coplanar situation,that the tether swings in the plane of the servicing spacecraft’s orbit,is studied.Numerical simulation verifies the effectiveness of the strategy proposed.

A New Generation of Intelligent Mapping and Remote Sensing Scientific Test Satellite Luojia-301

With the continuous improvement of the performance and the increasing variety of optical mapping and remote sensing satellites,they have become an important support for obtaining global accurate surveying and mapping remote sensing information.At present,optical mapping and remote sensing satellites already have sub-meter spatial resolution capabilities,but there is a serious lag problem in mapping and remote sensing information services.It is urgent to develop intelligent mapping and remote sensing satellites to promote the transformation and upgrading to real-time intelligent services.Firstly,based on the three imaging systems of the optical mapping and remote sensing satellites and their realization methods and application characteristics,this paper analyzes the applicable system of the intelligent mapping and remote sensing satellites.Further,according to the application requirements of real-time,intelligence,and popularization,puts forward the design concept of integrated intelligent remote sensing satellite integrating communication,navigation,and remote sensing and focuses on the service mode and integrated function composition of intelligent remote sensing satellite.Then expounds on the performance and characteristics of the Luojia-301 satellite,a new generation of intelligent surveying and mapping remote sensing scientific test satellite.And finally summarizes and prospects the development and mission of intelligent mapping remote sensing satellites.Luojia-301 satellite integrates remote sensing and communication functions.It explores an efficient and intelligent service mode of mapping and remote sensing information from data acquisition to the application terminal and provides a real service verification platform for on-orbit processing and real-time transmission of remote sensing data based on space-ground internet,which is of great significance to the construction of China’s spatial information network.

Thruster direction controlling of assembled spacecraft based on gimbal suspension

The attitude control system design and its control effect are affected considerably by the mass-property parameters of the spacecraft. In the mission of on-orbit servicing, as fuel is expended, or the payloads are added or removed, the center of mass will be changed in certain axe; consequently, some thrusters＇ directions are deviated from the center of mass（CM） in certain plane. The CM of assembled spacecraft estimation and thruster direction control are studied. Firstly, the attitude dynamics of the assembled spacecraft is established based on the Newton-Euler method. Secondly, the estimation can be identified by the least recursive squares algorithm. Then, a scheme to control the thrusters＇ directions is proposed. By using the gimbal installed at the end of the boom, the angle of the thruster is controlled by driving the gimbal; therefore, thrusters can be directed to the CM again. Finally, numerical simulations are used to verify this scheme. Results of the numerical simulations clearly show that this control scheme is rational and feasible.

GF-5 VIMI On-Orbit Calibration Instrument and Performance

The Visible and Infrared Multispectral Imager (VIMI) is one of the main payloads of the GF-5 satellite. It has 12 spectral bands covering the wavelength from visible light to thermal infrared. The imager designed life is 8 years. In order to monitor and correct the radiometric performance of the imager for a long time and meet the user’s demand for the quantitative remote sensing application, the expandable diffuser used for calibration in full FOV and full optical path method is designed. The solar diffuser is installed on the front side of the optical system and does not affect the normal imaging of VIMI. When VIMI need calibration, the diffuser is expand to the front of optical system via the driving mechanism. According to the characteristics of the GF-5 satellite orbit, the requirement of the calibration energy and the installation matrix of the imager relative to the satellite, the expansion angle of the diffuser is 39 degrees. The 430 mm × 430 mm large-size PTEE diffuser is manufactured to ensure full FOV and full optical path calibration. The diffuser’s directional hemispherical reflectance is higher than 95% from 420 nm to 2400 nm and variation of BRDF in the direction of imager observation is better than 2.5%. The diffuser stability monitoring radiometer is designed to monitor the on-orbit attenuation performance of the diffuser. Results of ground simulation experiments and preliminary on-board calibration experiments were introduced.

小卫星星座AIT过程进度风险管控探索与实践

针对小卫星星座项目在卫星总装、测试与试验(AIT)过程中进度拖延的问题,识别出一系列影响卫星生产进度的风险,结合星座项目的特点,提出了小卫星大批量AIT进度风险管控措施,在产品交付、总装与测试过程、资源分配等方面根据关键要素,制定了流程优化方案,经在某小卫星星座AIT过程中实践,结果表明:上述措施有效的将AIT过程进度风险降至可控范围,实现了小卫星星座项目在规定期限内高质量的完成研制任务,可以为今后大规模小卫星星座研制提供参考。

平板式“快集快响”微小卫星布局优化设计方法

针对平板式“快集快响”微小卫星转动惯量大的问题,提出一种基于级联遗传算法的“快集快响”微小卫星布局优化设计方法。该方法采用“迁移+交换+调整”3种操作规划部组件在卫星上的布局与安装位置,以降低卫星的转动惯量。其中,“迁移”操作用于完成部组件与功能板块的最优匹配,实现功能板块间的质量均衡;“交换”操作用于完成同一功能板块内部组件的最优布局;“调整”操作通过在小范围内微调部组件的位置,进一步扩大最优解的搜索范围,使卫星获得最优的转动惯量与布局方案。通过在仿真算例中与其他2种优化方法进行对比,所提方法的性能优势得到验证;并通过工程实例展示了所提优化方法的有效性。

基于在轨组装维护的多载荷协同观测卫星平台构型设计

针对高轨遥感卫星多载荷协同观测和一致测量应用需求,在前期总体技术方案研究的基础上,通过开展现有在轨组装航天器和高轨卫星公用平台的构型调研,提出了一种适用于多载荷协同观测需求的平台构型设计方案。平台利用CZ-5运载火箭发射并在轨展开,采用“网格式中心承力筒+板+桁架”式的总体构型,开展了主传力路径、贮箱承载结构、网格式中心承力筒等的细化设计工作,并进行了结构产品的初步设计,建立了平台结构整星的有限元模型。仿真分析表明:平台结构整星的各向一阶频率均能满足运载火箭的频率要求。基于标准化、通用化的平台接口设计,使其具备可扩展及可维修的能力,大大提升了平台鲁棒性。基于全网格筒的主承力设计,增强平台结构承载能力,并改善平台内部热环境。该设计方案可为基于在轨组装维护的高轨遥感大平台结构的设计提供有价值的参考。

小卫星批生产装配一致性控制方法

针对微小卫星批量化生产制造过程,分析了批生产质量管理特点和每组星之间的装配质量一致性影响因素.从工程实践的角度,提出了一种适于卫星系统批生产的装配一致性控制方法.该方法通过建立规范化体系、质量重心前移、提高工艺方法稳定性、固化技术状态、装配流程标准化、实施质量确认制、实行"去型号化"物资管理、引进自动化设备及统筹人员配置等质量控制手段,保证了小卫星批量化生产过程中装配工作的质量一致性.将其应用到卫星批产总装工作后,实践结果表明,卫星装配一致性控制方法能够有效提升批量化生产制造工作质量,大幅提升批次卫星产品的质量一致性,是卫星批量生产研制质量的有力保证.

太阳翼驱动机构对卫星姿态扰动特性评估

为了研究太阳翼驱动机构(solar array drive assembly,SADA)对卫星平台姿态的扰动特性,建立了考虑SADA驱动太阳翼旋转的整星姿态动力学模型,设计了一种测量SADA带载运动特性的试验方案。通过试验得到了SADA驱动负载的运动特性曲线,对试验数据进行拟合得到了SADA带载驱动的传递函数。将拟合的SADA运动模型代入到整星姿态动力学模型中进行仿真,得到了考虑SADA运动时的卫星姿态控制指标。基于SADA的运动特性和安装方式,设计了将两台SADA驱动信号的相位交错180°的扰动抑制策略。仿真验证了该策略对SADA运动的扰动抑制效果,具有良好的工程应用价值。

星罩组合体水平运输辅助支撑机构设计方案

针对星罩组合体水平运输条件下星箭分离装置的疲劳破坏问题,提出增加卫星辅助支撑机构的设计方案。建立辅助支撑机构力学模型,利用解析法计算得到辅助支撑机构设计的重要输入指标;并通过有限元仿真验证辅助支撑机构的性能是否满足使用要求。该辅助支撑机构的设计贯彻了从设计输入、建模、计算到验证的全流程研究方法,可为后续星罩组合体水平运输提供参考。

面向批产模式的小卫星构型与总装设计研究

中国小卫星的批量生产和发射大多集中在微纳卫星领域.目前,百千克级以上的小卫星设计制造只是对传统模式的改进优化,从构型及总装的设计上就决定了生产阶段无法实现大量批产.而国外具有代表性的批产型卫星构型并不适应中国单机的技术现状,载荷适应性较差.结合现阶段单机及总装的研制技术状态,提出了批产型小卫星构型和总装设计思路,分别从批发射、模块化、标准化、智能化及低成本5个方面阐述了适应批产模式的小卫星构型设计和总装设计的原则、方法,并在工程实践的基础上提出了发展思路,可供后续同类型小卫星构型与总装设计参考.

Two-Stage Identification Method for Attitude-Control Models of On-Orbit Satellites

A two-stage identification method was developed for attitude-control models of on-orbit satellites for accurate attitude control. The attitude-control models are based on a generalized attitude model （GAM） and its corresponding noise model （NM）. These are both low order models which are able to characterize the main satellite dynamics and the corresponding noise. These low-order attitude-control models facilitate improved controller design and state estimation. This identification approach uses two open-loop identification processes, with higher order auxiliary models used in the estimation for filtering and with the filtered signals used to identify the low order GAM and NM. An identification experiment with a micro-satellite simulator was used to verify the effectiveness of the two-stage identification method.

Study on Virtual Assembly for Satellite Based on Augmented Reality

Assembly activities are a very important part of the production processof large and complex equipment. In order to solve the huge resource problemof large and complex equipment assembly process, this paper proposes a virtualassembly for satellite.Microsoft’s latest holographic glasses HoloLens2 is used asa display facility, and Unity3D is applied to develop a satellite part assembly scenebased on augmented reality (AR) technology. Voice input and gaze in the MixedReality Toolkit (MRTK), provided by Microsoft, are adopted in the developmentscenario to enable users to interact with virtual models in a more natural way.Finally, the development scenario has been tested in a small space. The resultsshow its validity and good performance.

“高分二号”上相机和星敏感器相对安装姿态的测量

为了精确测量"高分二号"(GF-2)卫星上相机和星敏感器的相对安装姿态,建立了一套高精度自动化测量系统。针对该系统研究了基于多传感器数据融合的高精度测量算法、基于理论安装数据驱动的自动测量模型、以及基于图像识别的立方镜法线搜索算法。该测量系统主要由二维龙门导轨、精密转台和CCD成像辅助准直的自准直经纬仪构成,通过融合精密转台的转动角度、自准直经纬仪的俯仰角和偏航角等数据计算被测设备安装姿态角度。测量时需先对系统进行标定,制定自动测量规划,然后通过电机驱动使设备自动到达预定位置和角度进行测量。若星上设备安装偏差较大导致被测对象超出自准直经纬仪测量范围时,可启动CCD相机对被测对象局部区域进行搜索识别,并引导自准直经纬仪实现精确准直测量。对测量系统进行了实验验证,结果显示:该系统姿态测量精度可以达到5″,与标准值比对最大偏差为4.1″;该测量系统已用于GF-2卫星的相机和星敏器相对姿态测量中,重复标准差最大为3.5″,满足GF-2对机上设备安装姿态测量精度的需求。

基于Division Mockup的卫星虚拟装配系统研究与开发

以虚拟装配软件Division Mockup为平台,提出了卫星虚拟装配系统的体系结构,并在Division Mockup软件下完成了卫星产品的装配过程规划。针对Division Mockup只偏重于装配过程图形仿真的特点,开发了后端的卫星装配工艺生成系统,并通过数据接口实现了和Division Mockup的集成,从而完成工序工步规划、工艺文档生成、装配现场示教等功能。最后给出了系统的应用实例。

视觉与力觉结合的卫星部件机器人装配

针对卫星特殊部件的装配需求,为了使机器人具有适用不同工况的柔性并在卫星多变的装配工况中获得较高的应用效率,本文研究视觉引导与力反馈控制下的机器人装配技术,给出一种视觉与力觉结合的机器人装配方案:在装配孔位安装辅助销钉,通过视觉引导将部件引导至销钉的锥面导向范围内,而后在销钉导向下对机器人采用力反馈控制,实现工件的准确装配到位。采用红外相机结合合作靶标的方式实现稳定地视觉识别与目标定位,设计了探针式测量工具,并给出测量方法,实现了目标点位的柔性便捷测量。给出了一种已知空间对应点对条件下,求位姿变换矩阵及机器人目标位姿的计算方法。采用力/位混合控制方法实现柔顺销钉导向控制。实验结果表明:装配对应孔位的测量匹配误差在2.9 mm以内,机器人在视觉引导下,可以将工件运送至销钉的导向范围内,并在销钉导向及力反馈控制下将工件准确装配到位,力控制阈值为30 N。证明了本文所采用的技术可以满足卫星部件装配的工程实施要求。