“天绘一号”卫星在轨性能评估

“天绘一号”卫星是中国新一代传输型摄影测量卫星, 由航天东方红卫星有限公司基于CAST2000小卫星平台研制。01星于2010年8月发射成功, 02星于2012年5月发射成功。经过在轨测试, 两颗卫星性能指标均达到设计要求。本文介绍了“天绘一号”卫星在轨性能测试的结果, 为该卫星后续业务化应用提供宝贵数据。     

高分五号可见短波红外高光谱相机在轨辐射性能评估

对遥感器及其图像的在轨辐射性能(信噪比、相对辐射定标精度、绝对辐射定标精度和动态范围)评估是检验遥感器定量应用能力的重要任务之一。本文结合高分五号卫星可见短波红外高光谱相机AHSI (the Advanced Hyperspectral Imager)在轨性能评估任务,依据卫星发射以来的在轨测试数据,介绍了AHSI相机在轨辐射性能评估的原理、方法及相应测试情况。测试结果表明:AHSI信噪比可见近红外最高达到近700,短波红外最高达到近500;相对辐射定标精度误差小于0.5%,星上绝对辐射定标不确定度小于3%,场地绝对辐射定标真实性检验精度误差小于5%;动态范围在轨可见短波均可以256档增益精细调整。AHSI在轨辐射性能良好且稳定,能够有效支持后续定量化应用需求。     

Tracking and orbit determination performance of the GRAS instrument on MetOp-A

The global navigation satellite system receiver for atmospheric sounding (GRAS) on MetOp-A is the first European GPS receiver providing dual-frequency navigation and occultation measurements from a spaceborne platform on a routine basis. The receiver is based on ESA’s AGGA-2 correlator chip, which implements a high-quality tracking scheme for semi-codeless P(Y) code tracking on the L1 and L2 frequency. Data collected with the zenith antenna on MetOp-A have been used to perform an in-flight characterization of the GRAS instrument with focus on the tracking and navigation performance. Besides an assessment of the receiver noise and systematic measurement errors, the study addresses the precise orbit determination accuracy achievable with the GRAS receiver. A consistency on the 5 cm level is demonstrated for reduced dynamics orbit solutions computed independently by four different agencies and software packages. With purely kinematic solutions, 10 cm accuracy is obtained. As a part of the analysis, an empirical antenna offset correction and preliminary phase center correction map are derived, which notably reduce the carrier phase residuals and improve the consistency of kinematic orbit determination results.

An optimal determination of variable antenna height and power for in-orbit SAR operations

An optimal power and antenna height determination over a wide range of incidence angles is proposed for in-orbit operations of the spaceborne stripmap synthetic aperture radar (SAR) with variable antenna height and variable radiating element power. The antenna height and the average transmitted radio-frequency power of a radiating element for each incidence angle are determined so that the mapping area can be maximized with the constraints on the signal-to-noise ratio, ambiguities, and swath width, given the SAR geometry (an altitude and incidence angles) and radar wavelength. With the receive-chain power consumption of one transmit/receive module (P/sub r/=10 mW) and the SAR instrument power consumption without the phased array antenna (P/sub I/=5 W), the illustrative design example shows that the mapping area of the proposed SAR for the maximum incidence angle (/spl eta//sup max/=75/spl deg/) is about 269.1% of that resulted from utilizing only the variable antenna height. The proposed optimization would have a more beneficial effect on applications that need the high-incidence-angle operations.     

Space-borne BDS receiver for LING QIAO satellite: design,implementation and preliminary in-orbit experiment results

GPS Solutions - Known as China’s first low earth orbit (LEO) mobile communication experimental satellite, the LING QIAO satellite was launched on September 4, 2014. In addition to the two...     

电子水平仪精度分析与测试

文章介绍一种高精度电子水平仪的结构与测量原理,提出利用高精度二维转台对电子水平仪进行检定的新方法,并对电子水平仪的内符合精度、外符合精度以及稳定性进行精度分析。最后采用小角度检查仪检定和二维转台检定两种方法对电子水平仪的精度进行检定。实验结果表明,利用二维转台检定电子水平仪的方法能够满足电子水平仪的检定要求,与传统检定方法相比,该方法具有智能化、自动化和高效性等优点。     

陀螺经纬仪的仪器常数及其测定

仪器常数是陀螺经纬仪的一个重要指标,它的稳定性对仪器的定向精度影响很大。国产陀螺经纬仪的精度指标分为两类:一次定向的标准偏差和一次定向的中误差。前者是真正意义上的定向精度,后者只考核了仪器定向的重复性,不包含仪器常数的变化。目前业内对仪器常数的界定还有差异,造成在仪器使用中仪器常数混乱的状况。通过分析和对比讨论了仪器常数的实质内含,进而分析了影响仪器常数变化的因素,并针对仪器常数的测定提出了几点建议。     

论测量仪器的精密整平及对中技术

本文比较全面的阐述了用于仪器整平、对中的各种技术,给出了实现仪器精密整平、对中的方法。并分析了对中误差对不同边长的角度测量精度的影响,指出短边测量时,对中偏差会严重影响观测质量,最后展望了摆脱整平、对中问题的前景。     

恒星跟踪与人卫激光测距仪望远镜指向修正

望远镜的指向精度是人卫激光测距系统的一项重要指标 ,利用对恒星的观测可以修正望远镜的指向精度。本文介绍了在人卫激光测距观测中采用球谐函数模型对望远镜指向进行修正的一种方法 ,并用实际观测值验证了该方法的有效性     

Intersatellite laser ranging instrument for the GRACE follow-on mission

The Gravity Recovery and Climate Experiment (GRACE) has demonstrated that low–low satellite-to-satellite tracking enables monitoring the time variations of the Earth’s gravity field on a global scale, in particular those caused by mass-transport within the hydrosphere. Due to the importance of long-term continued monitoring of the variations of the Earth’s gravitational field and the limited lifetime of GRACE, a follow-on mission is currently planned to be launched in 2017. In order to minimise risk and the time to launch, the follow-on mission will be basically a rebuild of GRACE with microwave ranging as the primary instrument for measuring changes of the intersatellite distance. Laser interferometry has been proposed as a method to achieve improved ranging precision for future GRACE-like missions and is therefore foreseen to be included as demonstrator experiment in the follow-on mission now under development. This paper presents the top-level architecture of an interferometric laser ranging system designed to demonstrate the technology which can also operate in parallel with the microwave ranging system of the GRACE follow-on mission.     

Return pulse waveform simulation for LLRI instrument onboard Chandrayan-I

ISRO is launching a LiDAR instrument (LLRI) onboard Chandrayan-I. The LLRI will collect topographic data of lunar surface. Flying at an altitude of 100km the LLRI will have a footprint of 100m on the moon surface. Time of travel measurement, which is fundamental for topographic coordinate computation, depends upon the shape of the return pulse. This shape in turn is a function of the characteristics of footprint, i. e. its geometry, reflectance and roughness. This paper uses a mathematical model to simulate the return waveform at the receiver for different conditions of said characteristics within the footprint. Mathematical equations are employed to generate footprints that vary in their characteristics in terms of reflectance, geometry and roughness. A footprint is divided into small bins so that each bin has uniform property. Energy distribution in transmitted pulse is considered Gaussian. Energy irradiated over footprint is approximated using the assumed distribution. For each bin the energy incident is computed and accordingly the quantum and distribution of reflected energy is determined. The final waveform is generated by integrating the energy returned from all the bins according to their time of arrival and spread. Some results are presented to show the performance of the developed system.     

基于单片机的多功能手持GPS定位仪的设计

介绍基于STC89 C52单片机下的GPS信息的接收及输出显示,并利用SD卡对导航数据进行保存.采用GPS模块接收卫星信号,通过串口连接,既可通过单片机处理,然后在TFT彩屏上显示相关信息,也可与PC机通信,通过PC机应用软件显示GPS信息,也可通过PC版灵图电子地图实现实时导航.将SD卡保存的数据经GPSBabel软件转换,在googel earth地图上实现轨迹重现.实际应用效果表明,该设计合理有效,具有很高的实用价值.     

陆基增强系统与仪表着陆系统的空间对准

陆基增强系统(GBAS)与仪表着陆系统(ILS)输出的导航信息基准不同,若要利用数据融合技术实现二者的联合共用,首要问题就是对不同的导航信息进行空间对准.本文作者研究了 GBAS与ILS的偏移指示方式,详细推导了 GBAS与ILS的空间对准算法,开发了 X-Plane飞行数据交互分析系统.利用该系统从X-Plane中采...     

依托航空模拟平台的激光雷达技术课程实践教学装备

为了能更好地理解激光雷达技术工作原理与三维信息采集全过程,规避现有激光雷达技术,尤其是机载激光雷达,在实践教学中受场地限制的不利条件,本文依托于中国矿业大学(北京)沙河校区的航空模拟平台,自主研发了一套基于单线激光雷达与行程测距仪集成的三维激光扫描装备,阐述了该装备集成的数学原理,设计了三维数据采集实践教学方法,并进行了三维数据采集的实践体验与数据质量评价。结果表明,该装备采集三维点云的精度优于99%,可为激光雷达技术的实践教学、创新训练及本科毕业设计等环节提供有效的硬件支撑,并可在仓储方量核算等工程应用方面进行推广。     

CORS支持下的超站仪快速坐标测量算法分析

超站仪是全站仪和GPS接收机的一体化仪器,在CORS网络的支持下,可以实时得到仪器的厘米级精度坐标,通过距离交会,可以实现无定向点设站。文中对该方法做了分析,并进行精度评定。通过实验得出实测结果与理论分析一致,表明文中方法能够满足目前的应用部门对测量的精度要求,且算法简单,方便易行,能极大地提高作业效率,具有一定的工程应用价值。     

基于月球反射的遥感器定标跟踪监测

月亮辐照度是可见近红外波段一种稳定的辐射参考基准,对月观测已成为星载遥感仪器辐射定标和验证的一种新方法。风云三号03星(FY-3C)中分辨率光谱成像仪(Moderate Resolution Spectral Imager,MERSI)增加了对月观测功能,改进了太阳反射波段的在轨辐射定标。本文收集分析了MERSI在轨工作以来的全部11组对月观测数据,利用通道间辐照度比值方法移除月相角,日—月—星相对距离等因素对月亮辐照度观测值的影响,开展了可见光近红外波段的辐射定标工作,实现了MERSI太阳反射通道的辐射定标系数动态跟踪和评估。通过线性回归及统计发现,通道8辐射响应的年衰减率达到了14.55%,通道9达到了8.42%,通道1、6、10、11、16和19的年衰减率为1.15%—4.72%,其余通道未检测到衰减。研究结果可以用于订正MERSI数据的辐射定标系统性偏差,提高MERSI全寿命期的辐射定标精度。     

用于城市地下管井测量的摄影测量仪研制与试验

针对城市地下管井测量外业数据采集和处理非智能化、非数字化、费时费力、测量结果数据精度不准确等问题,文中以图像处理技术原理、摄影测量学原理、传感器技术原理为理论基础,研制出一种摄影测量仪。该仪器由CCD镜头相机、激光器、光源笔、PDA、云台,以及绝缘探测杆组成。利用Java语言以Android Studio2.2为开发平台开发出摄影测量解算程序。在地上便可测量,改变测量人员必须下井测量的传统工作模式,降低了作业危险和困难程度,经对6种18口地下井进行测量验证,直径测量相对误差为2.69%,长度测量相对误差为2.94%,宽度测量相对误差为2.47%,符合国家城市地下管线探测技术规程的精度要求。该仪器在城市工程测量以及相关领域具有很好的应用前景。