Method of SLAS’s ground track manipulation based on tangential impulse thrust

Satellites with altitudes below 400 km are called super low altitude satellites(SLAS),often used to achieve responsive imaging tasks.Therefore,it is important for the manipulation of its ground track.Aiming at the problem of ground track manipulation of SLAS,a control method based on tangential impulse thrust is proposed.First,the equation of the longitude difference between SLAS and the target point on the target latitude is derived based on Gauss’s variational equations.On this basis,the influence of the tangential impulse thrust on the ground track’s longitude is derived.Finally,the method for ground track manipulation of SLAS under the tangential impulse thrust is proposed.The simulation results verify the effective-ness of the method,after manipulation,the satellite can visit the target point and revisit it for multiple days.

典型轨道环境效应及对在轨卫星影响分析

近年来,各航天大国对空间轨道资源的挖掘与应用不断拓展。超低轨道、椭圆轨道、坟墓轨道、拉格朗日点等,因其在快速重访、定点观测、空间攻防、科学探索等方面的优势,逐步纳入各国防灾减灾、战事快响、导弹预警、空间突防和太阳观测等应用领域。随着卫星在轨经历的空间环境变得更加复杂,空间环境效应引发的卫星故障和异常情况日益突出。本文围绕目前国内外关注的五类典型轨道,对其主要环境特征、环境效应、地面模拟试验方法等进行了分析与讨论;梳理了各轨道关键敏感环境因素及典型环境效应,重点探讨了典型轨道下原子氧剥蚀、深层充放电、总剂量、单粒子等效应对卫星的影响;总结了相关地面模拟试验设备能力、试验方法适用性,并对后续发展提出建议。

航天拔尖人才特色班培养模式探索与实践——以哈尔滨工业大学“小卫星班”为例

哈尔滨工业大学针对我国航天领域高层次复合型人才的迫切需求,开设了院士担任班主任的特色班“小卫星班”,采用航天精神引领、多学科知识复合教学及航天工程实践教学融合的教学模式,致力于培养新时代的航天拔尖人才及战略科学家。思政教育方面,通过爱国主义教育,邀请航天总师座谈,充分依托“航天魂”“航天行”等思政实践活动,树立“爱党爱国、航天报国”信念;培养体系方面,实施“航天引领、专业任选”的知识复合型人才培养模式,采用本研一体、项目驱动的个性化课程培养体系,设置贯通式课程,实现多学科知识的融合教学与实践;素质能力方面,将航天工程组织管理与研制模式有机融入人才培养体系,依托紫丁香卫星创新工场,团队协作开展项目实施,使学生在航天高标准工程项目中锤炼能力。

基于NNBoost的卫星用复合材料层合板结构不确定性固有频率分析方法研究

为实现卫星用复合材料层合板固有频率的精确分析,综合考虑结构的加工误差、材料随机偏差等不确定性因素,研究并提出一种采用神经网络增强(Neural network boosting,NNBoost)模型对正交各向异性复合材料层合板固有频率进行不确定性分析的方法。将NNBoost模型作为固有频率求解与预测的代理模型,其目标函数设定为损失函数与正则项之和,求解过程中采用一种基于泰勒展开式的梯度下降方法更新权重和阈值以加速收敛。采用该方法,分析考虑输入参数随机性时正交各向异性复合材料层合板固有频率的统计特性。仿真试验结果表明,与直接蒙特卡洛模拟(Monte Carlo simulation,MCS)相比,采用NNBoost方法在保证预测精度的同时显著提高了求解效率;与传统反向传播(Back propagation,BP)神经网络方法相比,采用NNBoost方法预测结果的均方误差小于BP神经网络预测结果的均方误差且误差收敛更加平稳。

Hierarchical path planning for multi-arm spacecraft with general translational and rotational locomotion mode

On-orbit construction and maintenance technology will play a significant role in future space exploration.The dexterous multifunctional spacecraft equipped with multi-arm,for instance,Spider Fab Bot,has attracted a great deal of focus due to its versatility in completing these missions.In such engineering practice,point-to-point moving in a complex environment is the fundamental issue.This paper investigates the three-dimensional point-to-point path planning problem,and a hierarchical path planning architecture is developed to give the trajectory of the multi-arm spacecraft effectively and efficiently.In the proposed 3-level architecture,the high-level planner generates the global constrained centric trajectory of the spacecraft with a rigid envelop assumption;the middle-level planner contributes the action sequence,a combination of the newly developed general translational and rotational locomotion mode,to cope with the relative position and attitude of the arms about the centroid of the spacecraft;the low-level planner maps the position/attitude of the end-effector of each arm from the operational space to the joint space optimally.Finally,the simulation experiment is carried out,and the results verify the effectiveness of the proposed three-layer architecture path planning strategy.

Fault diagnosis of control moment gyroscope based on a new CNN scheme using attention-enhanced convolutional block

Control moment gyroscope(CMG)is a typical attitude control system component for satellites and mobile robots,and the online fault diagnosis of CMG is crucial because it determines the stability and accuracy of the attitude control system.This paper develops a data-driven CMG fault diagnosis scheme based on a new CNN method.In this design,seven types of fault signals are converted into spectrum datasets through short-time Fourier transformation(STFT),and a new CNN network scheme called AECB-CNN is proposed based on attention-enhanced convolutional blocks(AECB).AECB-CNN can achieve high training accuracy for the CMG fault diagnosis datasets under different sliding window parameters.Finally,simulation results indicate that the proposed fault diagnosis method can achieve an accuracy of nearly 95%in 1.28 s and 100%in 2.56 s,respectively.

Conceptual rotational mode design for optical conical scanning imaging small satellites

This paper focuses upon the novel optical conical scanning imaging working mode design for small satellites.This kind of satellite employs only one inclined optical camera achieving wide-swath imaging via a rotational motion about the nadir axis either by the camera or by the satellite.Three working modes are designed,i.e.,high-speed rotational mode,low-speed rotational mode,and variable-speed rotational mode.For the high-speed and low-speed working modes,the camera rotates at a constant speed and the corresponding angular velocity is derived under the consideration of guaranteed coverage and minimized overlap.To improve the system performance,an enhanced working mode taking advantages of both the high-speed rotational mode and lowspeed rotational mode is proposed.Working in this variable-speed rotational mode,the camera rotates slowly to get high-quality pictures when it works,while it rotates rapidly to reduce the energy consumption and save the storage during which period the camera is turned off to minimize the overlap.All these working modes are illustrated in detail,and numerical simulation tests are conducted to validate their effectiveness.

Tangent-impulse transfer from elliptic orbit to an excess velocity vector

The two-body orbital transfer problem from an elliptic parking orbit to an excess veloc-ity vector with the tangent impulse is studied. The direction of the impulse is constrained to be aligned with the velocity vector, then speed changes are enough to nullify the relative velocity. First, if one tangent impulse is used, the transfer orbit is obtained by solving a single-variable function about the true anomaly of the initial orbit. For the initial circular orbit, the closed-form solution is derived. For the initial elliptic orbit, the discontinuous point is solved, then the initial true anomaly is obtained by a numerical iterative approach; moreover, an alternative method is proposed to avoid the singularity. There is only one solution for one-tangent-impulse escape trajectory. Then, based on the one-tangent-impulse solution, the minimum-energy multi-tangent-impulse escape trajectory is obtained by a numerical optimization algorithm, e.g., the genetic method. Finally, several examples are provided to validate the proposed method. The numerical results show that the minimum-energy multi-tangent-impulse escape trajectory is the same as the one-tangent-impulse trajectory.