遥感SiCH-2卫星光学系统“猫眼”效应的卫星激光测距

乌克兰地球遥感卫星SiCH-2由2011年发射升空,目前已停止工作,处于失效失控状态,作为空间碎片目标由北美防空司令部（NORAD）提供两行根数（TLE）预报.本文分析了光学系统的“猫眼”效应,以上海天文台卫星激光测距（SLR）系统实现对SiCH-2卫星进行激光测距,测量回波强度大,测距精度优于10 cm.测距能力表明SiCH-2对激光反射回波达到合作目标带反射器的卫星激光测距水平,与光电探测设备“猫眼”效应分析的探测能力相当,测距数据结果表明该卫星处于自转状态,自转周期为4.3 s.本文国内外首次实现基于“猫眼”效应对在轨目标的激光测距,为远距离空间目标的探测提供了新的方法,促进高精度激光探测技术的应用发展,有利于对失效或轨道异常的光学系统类光电探测系列卫星进行监视监测.     

基于多颗低轨卫星的SLR台站坐标几何解算方法

卫星激光测距（SLR）技术作为卫星精密定轨手段和轨道检核重要方法,激光反射器已经成为重力卫星和测高卫星等低轨卫星的基本载荷.经典的SLR台站坐标是使用动力学方法计算的,本文根据多颗低轨卫星（LEO）多历元的激光观测数据,采用几何方法开展地面SLR测站坐标计算.通过组建低轨卫星群实现对全球激光站的动态观测,为了合理配置不同低轨卫星间观测值权重,削弱低轨卫星群可能存在的系统性偏差,提出采用方差分量估计组合的最小二乘法进行解算.实测结果显示,解算出SLR台站坐标框架解与SLRF2014差异平均值在25.1 mm,外符合精度达到1~2 cm.该方法避免了复杂动力学模型,SLR台站坐标的几何计算方法既可以作为激光测站框架解算手段之一,同时将LEO卫星群作为空间并址站实现不同技术地球参考框架间的融合.     

基于星载GPS的HY-2卫星高精度精密定轨模拟研究(英文)

HY-2卫星是我国第一颗测高卫星,其径向定轨精度要求厘米量级,搭载了星载GPS接收机。目前HY-2还处于测试阶段,没有公布观测数据。为了确定基于星载GPS的HY-2精密定轨流程及其定轨精度,本文模拟了HY-2卫星星载GPS观测数据,结果表明HY-2星载GPS天线每个历元至少观测7颗GPS卫星。给出了基于星载GPS的精密定轨流程,分别采用简化动力学方法和动态几何法进行了精密定轨实验。对于相位1mm和3mm随机误差的相位观测数据,简化动力学法和动态几何法定轨都能够实现厘米量级的径向精密定轨,几何法定轨精度略低于简化动力定轨。地球重力场模型是影响HY-2卫星精密定轨的重要因素,本文对不同阶次的重力场模型EIGEN2、EGM96、TEG4和GEMT3进行了简化动力学定轨实验,高于50阶次的重力场模型都能够实现厘米级径向精密定轨,主要原因在于大量的高精度星载GPS观测数据和重力场模型精度的提高。     

基于地面重力的卫星重力梯度检校方法

卫星重力梯度仪在轨检校是提高梯度模式重力卫星观测质量的关键.本文面向中国未来梯度模式重力卫星规划任务,研究提出一种基于地面重力的卫星在轨检校方法,该方法顾及卫星设计指标,从地面先验重力数据的精度、空间尺度以及卫星重力梯度仪的观测噪声等卫星检校要素开展分析研究,成功实现地面数据与卫星观测数据的比对检校.研究结果表明,在12°×12°的地面检校区域内,利用精度优于1 mGal的地面重力观测数据即可实现噪声低于10 mE的重力梯度仪高精度在轨检校.     

曲靖非相干散射雷达观测研究进展与展望

本文介绍了我国曲靖非相干散射雷达的主要技术方案，结合实测数据分析表明该雷达具备了电离层电子密度与等离子体温度观测、空间碎片凝视探测与月球二维成像探测等能力，可用于研究电离层F层气候学特征、电子密度暴时变化与异常增强等天气事件、E-F谷区结构与变化、约3 cm以上尺寸空间碎片的分布特征与模型、月球不同区域的散射回波特性等.下一步将重点开展低电离层与北驼峰结构及演化过程、电离层暴时与扰动特性观测.     

FY2D卫星与GOES卫星空间粒子观测结果的对比分析

风云二号D星(FY2D)搭载的空间粒子探测器可以观测10～300 MeV的质子和≥350 keV与≥2 MeV的电子.卫星在轨测试阶段,空间粒子探测器观测到了空间环境宁静期间地球同步轨道的电子昼夜周期变化的典型特征,并在卫星发射后的12月15日首次观测到了有代表性的 2级太阳质子事件(SEP),观测到的较高能量质子比较低能量质子更快地恢复到平静时的状态.通过比较FY2D卫星与GOES卫星的探测结果,既显示了同步轨道区域不同位置高能电子通量扰动时间的一致性,也显示了高能电子通量具强烈的晨昏不对称性.通过对太阳质子事件和地磁平静时期该轨道空间高能粒子环境特征的分析和研究,并与GOES卫星同期的观测结果进行相关性分析,结果表明仪器确实具备了监测空间环境扰动和预警能力,探测结果可以用于研究地球同步轨道粒子空间分布、起源和传输等科学目的.     

风云二号F星太阳X射线探测器在轨探测初步成果

风云二号系列卫星以自旋稳定方式工作于地球静止轨道,太阳X射线探测器是该系列卫星的重要有效载荷,监测太阳耀斑爆发过程,并对太阳质子事件等灾害性的空间天气事件进行预警.卫星自旋一周,该探测器完成一次全日面观测,记录太阳X射线的能谱与流量.2012年初,太阳活动进入第24周峰年,风云二号卫星太阳X射线探测器的在轨运行取得了良好的观测结果.相比于过去的太阳X射线探测器,风云二号F星的太阳X射线探测器应用了硅漂移探测(Silicon Drift Detector,SDD)技术,对GEO轨道海量的高能带电粒子采取了有效的屏蔽措施,可以对更"软"的X射线进行观测,能谱分辨率本领达到国际先进水平,对太阳耀斑的量化定级精度更高,在轨初步观测结果表明,精确的能谱探测能力可提高太阳质子事件预警能力,能道响应的时间特性比过去的探测数据更准确地反映了太阳耀斑的加热过程和带电粒子加速特性.本文介绍了风云二号F星太阳X射线探测器的设计及其发射前的标定试验结果,并且对发射后在轨运行获得的初步探测成果进行分析和讨论.     

用于灾后遥感的共位衍射卫星隔离方法

针对地震发生后对受灾地区高精度地图的获取需求,考虑到静止轨道轨位的紧张性,研究了一种基于共位衍射的卫星成像系统。该系统由两颗共位卫星构成,一颗为成像卫星,另一颗为薄膜衍射卫星,相比于传统的单颗成像卫星,该系统具有响应迅速以及空间分辨率高的优势。本文基于共位策略和隔离策略相结合的设计原则,采用倾角/偏心率协调隔离的方法,设计了一组轨位在10. 6E定点经度内的共位衍射成像系统轨道根数。通过仿真分析,将各个共位卫星之间相对距离与实际在轨卫星的相对距离做对比,仿真结果与实际数据间的误差满足一定的设计要求。因此,该组轨道根数在实际在轨应用中具备一定可行性,本文设计的共位衍射卫星系统为灾后应急响应提供重要参考。     

低轨磁测卫星干扰磁场标定方法研究

为了提高空间磁场探测精度,磁测卫星一般将磁强计安装在长伸杆的顶端,同时通过整星磁洁净控制,来减小磁强计安装位置的磁场干扰量.针对低轨磁测卫星的特点,提出零磁场环境下卫星极弱干扰磁场的高精度测量方法,模拟在轨地磁场环境下卫星感应磁场的标定方法,以及磁力矩器剩磁不确定量的处理方法.通过以上方法对卫星本体产生的干扰磁场实施严格的标定和数据修正,可有效减小其影响,极大提升空间磁场探测精度.该方法已应用于电磁监测卫星,将整星的磁场干扰不确定量降低一个量级,达到优于0.3 nT的水平.     

电磁卫星地震应用进展及未来发展思考

法国DEMETER(Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions)卫星是世界上第一颗专门针对地震电离层扰动监测的电磁卫星, 于2004年发射, 2010年底结束运行, 共在轨飞行6.5年, 获得3万多条整轨数据, 为地震监测及电离层物理研究提供了坚实的数据基础。 全球科学家利用这颗卫星的数据开展了大量的地震应用研究, 发表文章上百篇, 将电磁卫星的地震应用研究推向了新的阶段。 中国第一颗电磁监测试验卫星CSES(China Seismo-Electromagnetic Satellite)于2018年2月2日成功发射, 目前已完成在轨测试并交付使用, 科学数据也已正式对外发布。 如何充分发挥CSES卫星的应用效能, 将空间电磁监测向业务化运行转化, 总结和思考DEMETER卫星的技术进步、 研究成果及曾经出现过的问题, 十分重要。 因此, 本文着重介绍DEMETER卫星在地震监测应用领域的代表性研究进展, 并结合CSES卫星的设计和运转实践, 对未来空间地震电磁探测及科学研究的发展方向进行一些初步讨论。     

Pendulum-type laser strainmeter

Constructive disposition principles of the basic optical units of Michelson interferometers are used in making one-coordinate laser strainmeters of unequal-arm type.The fundamental advantages of pendulum-type laser strainmeter more than classical-type laser strainmeter are displayed.     

Towards a protocol for laser scanning of rock surfaces

The precision of height measurements derived from laser scanning a weathered rock surface was analysed. Different registration methods for comparing surfaces to deduce weathering were assessed and the most precise was found to be the method that used registration shapes as control, located in different planes relative to the scanned surface. In addition, the different sources of error in scanning precision were assessed by varying factors such as scan distance, lens configuration, scan angle and the nature of the topography being scanned. From this analysis it was possible to suggest what the optimal scanning conditions were for this particular experimental set‐up. The procedures outlined for assessing errors in the precision of height measurements are transferable to other scanning studies. Copyright © 2010 John Wiley & Sons, Ltd.     

Assessment of micro‐aggregation using laser diffractometry

In order to evaluate the influence of the measuring technique on the determination of (micro‐)aggregation in soil and sediment samples, results of grain size distributions of undispersed silty soil samples obtained by the sieve‐pipette method are compared with those obtained using a laser diffraction grain size analyser, the Coulter LS‐100. Reduced major axis relationships are calculated which may be used to convert Coulter LS‐100 results to those obtained by the sieve‐pipette method. The relationships obtained are very similar to the reduced major axis relationships established for dispersed silty soil samples. The results also show that the Coulter LS measurements have a systematic bias compared to the sieve‐pipette data. This implies that, if the percentage of (micro‐)aggregation is determined, the (interpretation of the) results will be strongly dependent on the measurement technique used. Using the calibration relationships that were established, nomographs can be developed to predict the level of sieve‐pipette (micro‐) aggregation from Coulter LS‐100 data. Copyright © 1999 John Wiley & Sons, Ltd.     

Application of laser strainmenters to the study of earthquake physics

The paper considers possibilities of applying laser strainmeters for the study of earthquake physics. One of laser strainmeters is described. A high efficiency of using the laser strainmeters for the study of earthquakes and their precursors is shown. In records of the spaced laser strainmeters, anomalous deformations propagating from the east to the west with the speed comparable with that of migration of earthquakes were found.     

基于激光干涉的新型高精度绝对重力仪

本文介绍了一种自主研发的新型高精度绝对重力仪样机,它利用激光干涉原理测量落体自由下落时相对于参考棱镜的时间位移信息,通过振动误差补偿算法提取落体下落轨迹上的时间位移坐标,然后基于最小二乘拟合法计算测点的重力加速度.在白家疃国家地球物理观象台国家重力基准点进行的对比观测试验结果与误差分析确定,样机经误差修正后的系统偏差为(-27.46～-30.59)±3.06×10-8 ms-2,2小时测量精度优于10×10-8 ms-2.     

Review of the development of laser fluorosensors for oil spill application

As laser fluorosensors provide their own source of excitation, they are known as active sensors. Being active sensors, laser fluorosensors can be employed around the clock, in daylight or in total darkness. Certain compounds, such as aromatic hydrocarbons, present in petroleum oils absorb ultraviolet laser light and become electronically excited. This excitation is quickly removed by the process of fluorescence emission, primarily in the visible region of the spectrum. By careful choice of the excitation laser wavelength and range-gated detection at selected emission wavelengths, petroleum oils can be detected and classified into three broad categories: light refined, crude or heavy refined.

This paper will review the development of laser fluorosensors for oil spill application, with emphasis on system components such as excitation laser source, and detection schemes that allow these unique sensors to be employed for the detection and classification of petroleum oils. There have been a number of laser fluorosensors developed in recent years, many of which are strictly research and development tools. Certain of these fluorosensors have been ship-borne instruments that have been mounted in aircraft for the occasional airborne mission. Other systems are mounted permanently on aircraft for use in either surveillance or spill response roles.     

Rapid uranium-series age screening of carbonates by laser ablation mass spectrometry

Uranium-series dating is a critical tool in quaternary geochronology, including paleoclimate work, archaeology and geomorphology. Laser ablation (LA) methods are not as precise as most isotope dilution methods, but can be used to generate calendar ages rapidly, expanding the range of dating tools that can be applied to late Pleistocene carbonates. Here, existing LA methods are revisited for corals (cold- and warm-water) and speleothems spanning the last 343 thousand years (ka). Measurement of the required isotopes (²³⁸U, ²³⁴U, ²³⁰Th and ²³²Th) is achieved by coupling a laser system to a multi-collector inductively-coupled-plasma mass spectrometer (MC-ICPMS) using a combination of a single central ion counter and an array of Faraday cups. Each sample analysis lasts for ∼4.3 min, and fifty samples can be measured in 12 h with an automated set up, after a day of sample preparation. The use of different standard materials and laser systems had no significant effect on method accuracy. Uncertainty on the measured (²³⁰Th/²³⁸U) activity ratios ranges from 5.4% to 7.6% for (²³⁰Th/²³⁸U) ratios equal to 0.7 and 0.1 respectively. Much of this uncertainty can be attributed to the heterogeneity of the standard material (²³⁰Th/²³⁸U) at the length scale of LA. A homogeneous standard material may therefore improve measurement uncertainty but is not a requirement for age-screening studies. The initial (²³⁴U/²³⁸U) of coral samples can be determined within ∼20‰, making it useful as a first indicator of open-system behaviour. For cold-water corals, success in determination of (²³²Th/²³⁸U) – which can affect final age accuracy – by LA depended strongly on sample heterogeneity. Age uncertainties (2 sigma) ranged from <0.8 ka at 0–10 ka, ∼1.5 ka at 20 ka to ∼15 ka at 125 ka. Thus, we have demonstrated that U-series dating by LA-MC-ICPMS can be usefully applied to a range of carbonate materials as a straightforward age-screening technique.     

Application of boat‐based laser scanning for river survey

The boat‐based, mobile mapping system (BoMMS) with a laser scanner allows the derivation of detailed riverine topographical data for fluvial applications. Combined with data acquisition from static terrestrial LiDAR (light detection and range) or mobile terrestrial LiDAR on the ground, boat‐based laser scanning enables a totally new field mapping approach for fluvial studies. The BoMMS approach is an extremely rapid methodology for surveying riverine topography, taking only 85 min to survey a reach approximately 6 km in length. The BoMMS approach also allowed an effective survey angle for deep river banks, which is difficult to achieve with aerial or static terrestrial LiDAR. Further, this paper demonstrates the three‐dimensional mapping of a point‐bar and its detailed morphology. Compared with the BoMMS surface, approximately, 80% and 96% of the terrestrial LiDAR points showed a height deviation of less than 2 cm and 5 cm, respectively, with an overall standard deviation of ± 2·7 cm. This level of accuracy and rapidity of data capture enables the mapping of post‐flood deposition directly after a flood event without an extensive time lag. Additionally, the improved object characterisation may allow for better 3D mapping of the point bar and other riverrine features. However, the shadow effect of the BoMMS survey in point bar mapping should be removed by additional LiDAR data to acquire entire riverine topography. The approach demonstrated allowed a large reach to be surveyed compared with static terrestrial LiDAR and increased the spatial limit of survey towards aerial LiDAR, but it maintains the same or even better temporal resolution as static terrestrial LiDAR. Copyright © 2009 John Wiley & Sons, Ltd.     

Towards a protocol for laser scanning in fluvial geomorphology

Advances in spatial analytical software allow digital elevation models (DEMs) to be produced which accurately represent landform surface variability and offer an important opportunity to measure and monitor morphological change and sediment transfer across a variety of spatial scales. Many of the techniques presently employed (aerial LIDAR, EDM theodolites, GPS, photogrammetry) suffer coverage or resolution limitations resulting in a trade‐off between spatial coverage and morphologic detail captured. This issue is particularly important when rates of spatial and temporal change are considered for fluvial systems. This paper describes the field and processing techniques required for oblique laser scanning to acquire 0·01 m resolution digital elevation data of an upland reach of the River Wharfe in the UK. The study site is variable with rapidly changing morphology, diverse vegetation and the presence of water, and these are evaluated with respect to laser data accuracy. Scan location, frequency and distance are discussed with reference to survey accuracy and efficiency, and a field protocol is proposed. Scan data cloud merging was achieved with a high degree of precision (sub‐centimetre) and positional data are shown to be very accurate for exposed surfaces. Vegetation and water decrease the accuracy, as the laser pulse is often prevented from reaching the ground surface or is not returned. Copyright © 2006 John Wiley & Sons, Ltd.