Creation of the new industry-standard space test of laser retroreflectors for the GNSS and LAGEOS

We built a new experimental apparatus (the “Satellite/lunar laser ranging Characterization Facility”, SCF) and created a new test procedure (the SCF-Test) to characterize and model the detailed thermal behavior and the optical performance of cube corner laser retroreflectors in space for industrial and scientific applications. The primary goal of these innovative tools is to provide critical design and diagnostic capabilities for Satellites Laser Ranging (SLR) to Galileo and other GNSS (Global Navigation Satellite System) constellations. The capability will allow us to optimize the design of GNSS laser retroreflector payloads to maximize ranging efficiency, to improve signal-to-noise conditions in daylight and to provide pre-launch validation of retroreflector performance under laboratory-simulated space conditions. Implementation of new retroreflector designs being studied will help to improve GNSS orbits, which will then increase the accuracy, stability, and distribution of the International Terrestrial Reference Frame (ITRF), to provide better definition of the geocenter (origin) and the scale (length unit).     

Laser sounding of aerosols using airborne and space facilities

The paper presents the results of laser sounding of water droplet crystal and mixed clouds carried out using an airborne lidar. A new method of determining the phase state of a cloud is described. The results are given on numerical experiments of laser sounding of various clouds using a polarization lidar for large variety of geometrical parameters of sounding schemes and optical characteristics of clouds. Numerical simulation of the results of laser sounding of aerosols from outer space for different lidar parameters and geometrical schemes of sounding is carried out using new models of vertical profiles of aerosol characteristics.     

Lunar laser topography by LALT on board the KAGUYA lunar explorer – Operational history,new topographic data,peak height analysis of laser echo pulses

In this paper we review the lunar laser ranging conducted by the laser altimeter (LALT) on board the KAGUYA lunar explorer (2007–2009). Five aspects of LALT measurements are described: (1) General operational history, (2) Laser shot and data statistics, (3) Revisions to LALT topographic data, (4) Variations in laser output energy, and (5) Peak height analysis of laser echo pulses. LALT was able to range to the lunar surface despite some troubles with respect to laser output energy in the middle of the KAGUYA mission. The time series topographic data set was revised (Ver. 2) by incorporating new lunar gravity model based on KAGUYA and other historical lunar satellite’s orbit data, along with other improvements, for example by incorporating the accurate position of the laser collimator on board the KAGUYA; however, more than half of the acquired range data could not be converted properly due to problems with orbit accuracy during the extended phase of the mission. The spherical harmonic coefficients and the basic lunar figure parameters derived from LALT_LGT_TS agree very well with LRO-LOLA and the Chang’E-1 LAM model. It is possible that partial failure to the laser diode was responsible for the gradual degradation of laser power (0.835 mJ per million shots) and the rapid decrease that occurred over April 9–14, 2008. The laser power also proved to be extremely sensitive to the temperature of the laser oscillator. The peak height ratio – that is peak height telemetry data divided by calculated ratio – is about 19% on average using the mean slope and albedo data from LALT and Spectral Profiler on KAGUYA space craft, respectively, which suggests the performance of peak height measurement is more than 1/5 for more than 70 km altitude, if compared with calculated one. The peak height ratio may be better if we take the effect of small scale topography within a footprint into account.     

脉冲激光模拟空间载荷单粒子效应研究进展

脉冲激光作为模拟测试空间探测载荷半导体器件的单粒子效应现象的一种较新型手段,具有可以定位器件对单粒子效应敏感的具体单元以及动态测试电路系统对单粒子效应的时间响应特性的特点,能够满足工程部门、器件研发部门的不同需求。通过实验与理论研究,建立单粒子锁定与翻转效应的激光阈值能量与重离子LET值的对应关系,解决了脉冲激光模拟测试的激光结果如何定量的关键问题,据此可以定量摸底评估器件的单粒子效应敏感度,使脉冲激光测试载荷的结果更具评价以及指导意义,这对建立统一的脉冲激光单粒子效应评估试验标准以及对脉冲激光试验的推广具有重要意义。空间探测载荷发生单粒子效应后器件功能特性及电路系统的影响、防范单粒子效应电路条件影响的手段下电路系统的抗单粒子效应设计措施是的有效性,以及为空间探测专门研制的抗辐射ASIC电路评价,都需要更加精细的单粒子效应测试方法。通过建立便捷、低成本的脉冲激光定量试验的手段,解决了空间探测载荷上述单粒子效应试验的问题。     

304不锈钢旋转双焦点激光-TIG复合焊接

为了提高激光-电弧复合焊接质量,提出了一种新的焊接方法——旋转双焦点激光-TIG(Tungsten Inert Gas)复合焊接.运用自行研制的旋转双焦点激光-TIG复合焊接头对304不锈钢进行了不同焊接参数下的工艺试验,并分析了焊接参数对焊缝成形的影响.结果表明在旋转双焦点激光-TIG复合焊接过程中,焊接电流和激光功率的大小和相互配合是2个热源能否有效耦合的关键因素,而旋转频率的大小对焊缝的熔深、熔宽影响不大,通过旋转双焦点激光和电弧的耦合作用可以有效地提高焊接热源的利用率.      

量子阱激光器的Pspice电路温度模型

在考虑量子阱激光器的温度特性基础上,对激光器的速率方程进行了适用性修正,增加了与温度相关的势垒区的辐射复合电流I_br、非辐射复合电流I_bnr和有源区的非辐射复合电流I_wnr、俄歇复合电流Ia等项,并根据修正后的速率方程得出了量子阱激光器的大信号等效 Pspice电路温度模型和直流稳态工作时的等效Pspice电路温度模型,然后采用GaAS/AlGaAS 量子阱激光器,根据量子阱激光器直流稳态工作时的等效Pspice电路温度模型对量子阱激光器的输出光功率、驱动电流和结点温度之间特性进行了模拟,得出它们之间的关系曲线.     

一种三维激光扫描系统的设计及参数标定

基于三维激光扫描系统的移动机器人动态环境地图构建技术是机器人智能感知技术的重要组成部分,而三维激光扫描系统的设计及标定技术对于地图构建的精度有决定性的影响。针对应用于小型移动机器人的三维激光扫描系统低成本、小型化的需求,设计了一套由高精度旋转云台和小型二维激光测距传感器组成的三维激光扫描系统,并提出了一种新的系统参数标定方法以提高三维扫描测量的准确度。该方法使用镂空圆孔标定板作为标定对象以完成对三维扫描特征自动准确获取,并根据非线性最小二乘法对三维激光扫描系统的参数进行优化计算。实验结果表明,所设计的三维激光扫描系统能够准确地测量周围环境的三维信息,实现了以低成本获得高质量环境建模的三维扫描数据技术。      

转台中心轴线标定误差分析与修正

提出一种标定球和几何变换相结合的方法修正三维激光数字化系统中转台中心轴线的标定误差.该方法首先用8个不同旋转位置的标定球球心计算转台中心轴线,然后利用几何变换将不同位置的球心绕转台中心轴线旋转到零度位置,并计算与初始位置球心的偏差,依据不同位置球心旋转复位的偏差采用几何逆变换推导出转轴偏心的修正公式.在自行设计的三维激光线扫描测量平台上数据旋转拼合精度提高到0.07?mm,实现了多视旋转测量的数据点云在线自动拼合.与以前的方法相比,设计的转轴标定误差修正方法简单、高效,在其它安装转台的测量系统中同样适用.     

基于激光测振仪分离装置测量方法研究

针对目前采用的高速摄像测量方法存在误差较大与操作困难问题,提出了一种基于激光测振仪的新型测量方法,可以有效提高分离装置试验测量精度,为后续分离装置机构精确设计奠定基础。     

一种TeGe基快速相变型可逆光记录介质的研究

研制出一种在晶化激光功率为4mW时晶化时间为180ns的可逆相变型光纪录介质。其擦写循环次数可达10~6次。分析了其快速晶化机理。     

用激光干涉技术测量转速的研究

叙述了一种新型转速激光干涉测量方法,详细分析了这种方法的工作原理,确定了本测量方法的转速测量范围,给出了实验结果。     

基于PSD的触须传感器及在移动机器人中的应用

针对视觉传感器无法解决的移动机器人的全天候避障问题,设计了一种触觉传感系统.利用位置敏感探测器(PSD,Position Sensitive Detector)作为触须根部的检测元件,设计了一种机械结构,利用一个直接连接在触须根部并侧向出射激光的激光器,解决了触须安装困难以及安装误差对测量精度影响较大的问题;提出了两种全新的检测机器人本体与墙体之间夹角的方法,可实现机器人近墙行走,对两种方法的优劣进行了比较,最后通过实验证明了此两种方法的可行性,并对测量产生的误差进行了分析.     

激光测距通信一体化技术研究及深空应用探索

概述了空间激光测距通信一体化技术的研究现状,提出了一种激光精密测距与高速通信一体化技术,基于双向单程测距原理,在BPSK外差相干激光通信的基础上,采用码元相位测量实现了激光测距与通信一体化设计,并完成了地面实验验证。实验结果表明：在通信码速率1 Gbit/s的情况下,其测距精度优于0.9 mm,并分析了参考时钟频差对测距精度的影响。最后对激光测距通信一体化技术在未来深空探测中的应用进行了探索研究。     

超精密球度的激光干涉测量方法

传统的球度测量方法很难达到亚微米级的测量准确度。为此,提出了超精密球度激光干涉测量的新方法,介绍了测量装置的结构及测量原理,并给出了球面波和球度计算的数学模型。     

深空激光通信进展及应用研究

深空激光通信是实现深空高速通信的主要手段之一。对国外深空激光通信的发展现状进行了综述,总结了深空激光通信技术发展的若干启示,给出了深空激光通信的典型应用,分析了深空激光通信涉及的主要关键技术,以期为我国深空激光通信的发展提供一定的参考和借鉴。     

Accurate orbit predictions for debris orbit manoeuvre using ground-based lasers

Orbit manoeuvre of low Earth orbiting (LEO) debris using ground-based lasers has been proposed as a cost-effective means to avoid debris collisions. This requires the orbit of the debris object to be determined and predicted accurately so that the laser beam can be locked on the debris without the loss of valuable laser operation time. This paper presents the method and results of a short-term accurate LEO (<900 km in altitude) debris orbit prediction study using sparse laser ranging data collected by the EOS Space Debris Tracking System (SDTS). A main development is the estimation of the ballistic coefficients of the LEO objects from their archived long-term two line elements (TLE). When an object is laser tracked for two passes over about 24 h, orbit prediction (OP) accuracy of 10–20 arc seconds for the next 24–48 h can be achieved – the accuracy required for laser debris manoeuvre. The improvements in debris OP accuracy are significant in other applications such as debris conjunction analyses and the realisation of daytime debris laser tracking.     

Spacecraft formation flying for Earth-crossing object deflections using a power limited laser ablating

A formation flying strategy with an Earth-crossing object (ECO) is proposed to avoid the Earth collision. Assuming that a future conceptual spacecraft equipped with a powerful laser ablation tool already rendezvoused with a fictitious Earth collision object, the optimal required laser operating duration and direction histories are accurately derived to miss the Earth. Based on these results, the concept of formation flying between the object and the spacecraft is applied and analyzed as to establish the spacecraft’s orbital motion design strategy. A fictitious “Apophis”-like object is established to impact with the Earth and two major deflection scenarios are designed and analyzed. These scenarios include the cases for the both short and long laser operating duration to avoid the Earth impact. Also, requirement of onboard laser tool’s for both cases are discussed. As a result, the optimal initial conditions for the spacecraft to maintain its relative trajectory to the object are discovered. Additionally, the discovered optimal initial conditions also satisfied the optimal required laser operating conditions with no additional spacecraft’s own fuel expenditure to achieve the spacecraft formation flying with the ECO. The initial conditions founded in the current research can be used as a spacecraft’s initial rendezvous points with the ECO when designing the future deflection missions with laser ablation tools. The results with proposed strategy are expected to make more advances in the fields of the conceptual studies, especially for the future deflection missions using powerful laser ablation tools.     

超长桁架变形的多点实时测量方法研究CSCD

超长可伸展桁架结构广泛应用于各领域,对其变形测量有着重要意义,比较国内外现有的几种常见的超长可伸展桁架结构变形测量方法,指出现有方法的缺点和局限性。提出一种新的基于激光准直的无导轨超长桁架结构变形测量方法,以激光准直光束为测量基准,利用递进分光的方式,实现桁架结构的多点实时测量。分析方法原理后设计实验系统,完成初步测试,实验结果表明基于该方法的测量系统能测量桁架结构二维变形,且稳定性好,重复性误差小于1.1%,非线性误差小于0.6%。该方法无需采用移动的方式或利用导轨即可完成多点实时测量,环境适用性大大提高,还具有测量精度高、测量距离远、可拓展性好等优点,具有很好的发展前景。     

Mission feasibility analysis on deflecting Earth-crossing objects using a power limited laser ablating spacecraft

This paper analyzes several mission capabilities to deflect Earth-crossing objects (ECOs) using a conceptual future spacecraft with a power limited laser ablating tool. A constrained optimization problem is formulated based on nonlinear programming with a three-dimensional patched conic method. System dynamics are also established, considering the target ECO’s orbit as being continuously perturbed by limited laser power. The required optimal operating duration and operating angle history of the laser ablating tool are computed for various types of ECOs to avoid an Earth impact. The available final warning time is also determined with a given limited laser power. As a result, detailed laser operating behaviors are presented and discussed, which include characteristics of operating duration and angle variation histories in relation to the operation’s start time and target object’s properties. The calculated durations of the optimal laser operation are also compared to those estimated with first-order approximations previous studies. It is discovered that the duration of the laser operation estimated with first-order approximations could result in up to about 50% error if the operation is started at the final warning time. The laser operation should be started as early as possible because an early start requires a short operating duration with a small operating angle variation. The mission feasibility demonstrated in the present study will give various insights into preparing future deflection missions using power limited spacecraft with a laser ablation tool.     

Tumbling object deorbiting using spaceborne laser engagement – A CubeSat case study

This paper demonstrates active space debris removal using spaceborne laser systems. The laser beam and the surface of the target are discretised into multiple rays and finite elements, respectively, for laser-target interaction modelling, in which the laser ablation process is investigated. A high-fidelity attitude/orbit propagator tool is developed to account for both the linear impulse and angular impulse induced by the laser engagement and other perturbations. The laser system is activated only when three switch criteria are satisfied. In numerical simulations, laser pulses from international space station are generated to deorbit a 3U CubeSat with initially tumbling modes. The results validate the effectiveness of deorbiting tumbling CubeSats using spaceborne laser engagement, with the perigee height lowered by approximately $2.4\mathrm{km}$ in around $30\min$ after $2\mathrm{h}$ propagation. It is also found that the laser engagement becomes more effective for an initially faster rotating object.