The 1-Centimeter Orbit: Jason-1 Precision Orbit Determination Using GPS,SLR, DORIS,and Altimeter Data Special Issue: Jason-1 Calibration/Validation     

《Marine Geodesy》2013,36(3-4):399-421

The Jason-1 radar altimeter satellite, launched on December 7, 2001 is the follow on to the highly successful TOPEX/Poseidon (T/P) mission and will continue the time series of centimeter level ocean topography measurements. Orbit error is a major component in the overall error budget of all altimeter satellite missions. Jason-1 is no exception and has set a 1-cm radial orbit accuracy goal, which represents a factor of two improvement over what is currently being achieved for T/P. The challenge to precision orbit determination (POD) is both achieving the 1-cm radial orbit accuracy and evaluating the performance of the 1-cm orbit. There is reason to hope such an improvement is possible. The early years of T/P showed that GPS tracking data collected by an on-board receiver holds great promise for precise orbit determination. In the years following the T/P launch there have been several enhancements to GPS, improving its POD capability. In addition, Jason-1 carries aboard an enhanced GPS receiver and significantly improved SLR and DORIS tracking systems along with the altimeter itself. In this article we demonstrate the 1-cm radial orbit accuracy goal has been achieved using GPS data alone in a reduced dynamic solution. It is also shown that adding SLR data to the GPS-based solutions improves the orbits even further. In order to assess the performance of these orbits it is necessary to process all of the available tracking data (GPS, SLR, DORIS, and altimeter crossover differences) as either dependent or independent of the orbit solutions. It was also necessary to compute orbit solutions using various combinations of the four available tracking data in order to independently assess the orbit performance. Towards this end, we have greatly improved orbits determined solely from SLR+DORIS data by applying the reduced dynamic solution strategy. In addition, we have computed reduced dynamic orbits based on SLR, DORIS, and crossover data that are a significant improvement over the SLR- and DORIS-based dynamic solutions. These solutions provide the best performing orbits for independent validation of the GPS-based reduced dynamic orbits. The application of the 1-cm orbit will significantly improve the resolution of the altimeter measurement, making possible further strides in radar altimeter remote sensing.  相似文献   

New age-determination method based on fast growth rate of Cape hake Merluccius capensis in Namibia     

《African Journal of Marine Science》2013,35(2):119-124

Namibia’s most important commercial fisheries resource, the shallow-water Cape hake Merluccius capensis, is currently assessed using statistical catch-at-age analysis. Age data obtained from otoliths constitute an important data component of this model. Recent age-validation studies of M. capensis showed that growth was previously underestimated. We investigated this new fast-growth hypothesis (FGH) by using measurements and counts of translucent zones (T1 to T14, from otolith core to edge) on two survey otolith samples covering the entire range of fish lengths. We compared three hypotheses of periodicity of otolith zone formation and show that, if all zones are counted, T2 (at 9.0 mm otolith length), T5, T8, T11 and T14 are most likely to be annuli. A conversion from the slow-growth-hypothesis (SGH, currently used) age data was calculated as: FGH age group = round (0.41[SGH age group] + 0.25), and this formula should be applied to compute and test updated catch-at-age data in a future hake stock assessment. Additional adjustment for the hake stock assessment following the FGH, such as the timing of recruitment in winter and catches in summer, should be considered in future assessments.  相似文献   

论确定全球大地水准面的斯托克斯方法     

申文斌 《测绘学报》2012,41(5):670-675

确定全球大地水准面最常用的方法是斯托克司方法。然而,除了人们熟知的缺陷之外,斯托克司方法还存在人们没有意识到的理论困难：当大地水准面位于参考椭球（WGS84椭球）内部时,在大地水准面上及其与参考椭球面界定的区域中扰动位没有定义,当然在这部分区域也不调和。为了解决这一困难,可以选取一个包含在大地水准面内部的由四个基本参数唯一确定其外部正常重力位的参考椭球（简称内部椭球）,其中心与 WGS84 椭球的中心重合,其中的两个基本参数,旋转角速度和地心引力常数,与 WGS84 椭球面的相同,另外两个参数,半长轴和扁率,如此选取,使得内部椭球产生的新的正常重力位在 WGS84 椭球面上与大地水准面上的重力位 相等。这样,传统的斯托克司方法中存在的理论困难不复存在。  相似文献   

北斗多普勒测速精度的分析     

王拓  吕志伟  殷实  王贺 《测绘信息与工程》2012,37(2):16-19

介绍了原始多普勒观测值测速方法的数学模型,分析了各误差源对多普勒测速的影响,并使用北斗卫星导航系统实测数据在静态模式下对多普勒测速精度进行了分析。结果表明,目前使用北斗原始多普勒观测值测速精度可优于0.1m/s。  相似文献   

多源遥感与作物模型同化模拟作物物生长参数时空域连续变化   总被引：3，自引：1，他引：2  

吴伶  刘湘南  周博天  李露锋  谭正 《遥感学报》2012,16(6):1173-1191

本文将遥感信息与作物模型同化实现作物生长参数的时空域连续模拟,进而监测生长参数的时空域变化.首先将作物模型WOFOST(World food studies) 与冠层辐射传输模型PROSAIL 耦合构建WOPROSAIL 模型,利用微粒群算法(PSO) 通过最小化从CCD 数据获取的土壤调节植被指数观测值SAVI(soil adjusted vegetation index) 与耦合模型得到的模拟值SAVI’之间差值优化作物模型初始参数.通过MODIS 数据反演实现参数的区域化,并将区域参数作为优化后作物模型输入参数驱动模型逐像元计算生长参数,实现生长参数的时空域连续模拟与监测,最终建立区域尺度遥感-作物模拟同化框架模型RS-WOPROSAIL .结果表明：同化模型解决了作物模型模拟空间域和遥感信息时间域的不连续问题.模型模拟的叶面积指数(LAI) 、穗重(WSO) 、地上总生物量(TAGP) 等生长参数较好地体现了水稻生长状况时空域变化,研究区水稻模拟产量与实际产量的误差为27.4% .  相似文献   

GPS精度鉴定测姿系统中的闭合差检验     

姚飞娟  杜娟  孙中豪  宫帅帅 《全球定位系统》2012,37(4):40-43

简要介绍了GPS精度鉴定测姿系统构造原理,针对高动态条件下GPS精度评估与检验存在检核难的问题,设计了利用三角形闭合差进行检验方法,基于Visual C++编写了精度检验软件,经数据分析得出GPS高动态下的系统误差,该方法计算简单易于操作,有效利用了测姿系统冗余信息,具有较好的实用价值。  相似文献   

一种离焦模糊遥感图像盲复原方法   总被引：2，自引：0，他引：2  

姜明勇  陈向宁  喻夏琼 《测绘科学》2012,(4):135-137

由于发射过程中的超重和复杂的工作环境,遥感卫星的光学系统常发生像面离焦,直接影响了成像质量,降低了图像的空间分辨率。本文提出了一种大尺寸离焦模糊遥感图像的盲复原方法,用于提高这种图像的分辨率。该方法采用微分自相关法估计离焦半径,采用适用于大尺寸图像复原的连续Hopfield神经网络次优算法实现复原,结合能保留图像细节信息的调和模型,能较好地提高大尺寸离焦遥感图像的清晰度。仿真结果证实了方法的有效性。  相似文献   

基于星敏感器的遥感卫星姿态确定仿真系统实现     

施群山  徐青  蓝朝桢  李建胜  顾广杰  王平 《测绘科学》2012,37(5):204-206,221

为了在地面实验中研究基于星敏感器的遥感卫星姿态自主确定相关技术,本文在基于星敏感器的遥感卫星姿态确定半物理仿真系统工作原理的基础上,对整个系统的总体及各模块进行了详细的设计,最后建立了该半物理仿真系统,为多种目的服务。整个系统的建立能够为基于星敏感器的遥感卫星姿态确定技术新方法、新思路和新方案的研究提供参考。  相似文献   

一种适用于卫星导航系统星间链路的可抢占时隙TDMA体制     

石磊玉  周益  王东会  欧钢 《武汉大学学报(信息科学版)》2012,37(6):714-718

针对传统TDMA体制数据传输时延较大的缺点,提出了一种适用于卫星导航系统星间链路的可抢占时隙的TDMA体制,并抽象出了该TDMA体制下的时隙编排优化目标,结合卫星导航系统星座的星间可视性,以顶点着色为理论基础提出了一种优化的时隙编排算法。仿真结果表明,与GPS星间链路的TDMA体制相比,所提出的TDMA体制可达到相同的卫星自主定轨精度以及系统用户等效观测误差(URE)性能,同时大幅提高了系统通信性能。  相似文献   

IMU辅助X射线脉冲星的深空探测器精确定姿方法及仿真     

罗楠  许录平  张华  谢强 《武汉大学学报(信息科学版)》2012,37(9):1049-1054

为满足深空探测器的精确定姿需求,提出了一种惯性测量单元(IMU)辅助的X射线脉冲星定姿方法。该方法用IMU的速率陀螺来估计航天器短时姿态,观测两颗或多颗脉冲星的X射线辐射信号,将拟合得到的观测矢量作为滤波器信息输入,利用这两种测姿手段在时间和空间上的互补特性,提供一种全天候、抗干扰性强的定姿方法。仿真结果表明,相比于EKF,基于UKF的俯仰、横滚和偏航三姿态角的测量精度可提高21.9%、21.1%和31.7%;与仅使用脉冲星或IMU的定姿方法相比,组合定姿方法的俯仰角估计精度分别提高了32.5%和77.6%。  相似文献