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基于地球扁率红外地平仪测量值修正算法研究 总被引:4,自引:0,他引:4
根据对地球扁率引起红外地平仪测量值误差修正算法进行了研究,椭球地球模型矢量投影关系得到了地球扁率修正函数和姿态角计算公式。由于地平穿越点由地球表面方程、地平平面方程和扫描圆锥锥面方程唯一确定,采用了递推方法解算出地平穿越点处的几何量,所得结果通过扁率修正函数对姿态角进行实时修正。所提算法简单,易于星载计算机在线实现,仿真算例验证了该方法的有效性。 相似文献
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基于开普勒二体运动修正地球扁率J2摄动项算法 总被引:2,自引:0,他引:2
为了解决远程飞行器虚拟目标点的地球扁率J2摄动项修正的技术难点,提出一种基于开普勒二体运动推算地球引力模型J2摄动项的间接补偿的方法.该算法由基于二体运动时间推算J2摄动项飞行时间的计算模块和基于二体运动J2摄动落点修正2个计算模块构成.通过算法设计和数学仿真验证了算法的正确性,其中仿真结果表明,该算法有效解决地球扁率造成的虚拟目标点计算精度不足的问题,在算法层面与传统的地球扁率修正方法相比具有计算简单和计算速度快等优点,同时保证虚拟目标点计算达到精度要求. 相似文献
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为减小自主导航过程中地球红外辐射误差及地敏安装误差的影响,以星敏感器和地球敏感器的测量作为导航信息,提出了一种捷联惯导/天文信息组合的自主导航方案。针对地球大气辐射不均匀和地球敏感器安装误差对确定地心矢量的不利影响,建立了地球红外辐射亮度与等效地平高度的关系。利用这一关系,给出了对地球敏感器测量修正的函数关系以及地球敏感器安装误差估计方法。以恒星矢量和地心矢量的星间角距作为量测,采用批处理最小二乘方法对弹道导弹的导航信息进行了估计。仿真结果表明:通过对辐射误差的补偿可大幅提高自主导航的精度,验证了补偿方法的可行性和导航算法的有效性。研究为工程应用中修正地球红外辐射误差提供了一种新思路。 相似文献
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针对直接敏感地平的红外地平仪-星光导航系统精度低的问题,提出通过建立扁率误差补偿函数,研究扁率引起的姿态角测量误差;建立地心矢量的姿态角误差模型,通过修正地球扁率误差来补偿姿态角,对卫星施加姿态偏转指令调整地心矢量偏移。同时基于SODERN地球红外辐射模型,考虑红外辐射强度随纬度和季节的变化建立真实红外辐射曲线,通过滤波算法获得精确的地球切线边缘的量测信息,提高红外地平仪测量精度。仿真结果表明,该方法有效提高了基于红外地平仪的星光导航定位方法的可靠性和精度,导航位置误差能达到500m左右,较原有系统提高3倍以上。 相似文献
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红外成像敏感器代表了新一代敏感器的发展方向。本文介绍了红外成像敏感器光学系统工作原理,对红外成像敏感器光学系统进行简化,利用小孔模型完成了对敏感器光学系统的建模,分别在地球球形模型和旋转椭球模型下进行了地心矢量推导和计算,获得了焦平面内地平圆盘的相关参数的具体表达式,用牛顿迭代法对地心距进行数值计算,比较分析了球形模型与椭球模型在求解地心距精度上的差别,分析了敏感器测量误差对地心矢量精度的影响,以及焦平面内地平圆盘各参数分别对地心距计算精度的影响程度。 相似文献
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基于姿态敏感器的地球同步轨道卫星自主导航研究 总被引:1,自引:0,他引:1
本文提出了一种基于姿态敏感器的地球同步轨道卫星自主导航方法,作为解决未来高轨道卫星自主运行的先决条件。在整个系统中,以包含摄动项的HILL 方程作为状态方程,根据由姿态敏感器给出的卫星本体相对于地球和另外两个空间天体的方位,推导出测量方程,进而用简化的推广 Kalman 滤波算法进行状态估计。仿真表明,该方法收敛速度快,精度较高,是一种可行的地球同步轨道卫星自主导航方法。 相似文献
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随着人类活动的加剧与地球本身发展周期的影响,人类面临着愈来愈大的挑战。地球系统的全球化与对地观测技术的进步等推动了地球系统科学的产生和发展。为深刻认识全球变化,制订正确的政策,多个国家建立了对地观测系统。阐述了地球系统科学的主要内容,并以美国EOS和欧盟GMES为例,论述了对地观测计划及其发展趋势。 相似文献
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To date, NASA's “Near Earth Object Program” has discovered over 5500 comets and asteroids on trajectories that bring them within “the neighborhood” of Earth's orbit. Nearly 1000 of these objects are classified as “potentially hazardous,” passing within 0.05 astronomical units of Earth's orbit. Discovery rates of such threatening bodies increase each year. Given this multitude of threats, in addition to evidence that the planet has absorbed many impacts over its history, it is reasonable to assume that another object will strike the Earth at some point in the future. Consequently, researchers have studied and proposed several mitigation techniques for such an occurrence. This study seeks to determine how effectively the attachment of a tether and ballast mass would divert the trajectory of such threatening objects. Specifically, the study analyzes the effects over time of such a system on objects of varying orbital semimajor axis and eccentricity, using various tether lengths and ballast masses. It was determined that the technique is most effective for NEOs with high eccentricity and small semimajor axis, and that system performance increases as tether length and ballast mass increase. 相似文献
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外太空遍布小行星,它们肆无忌惮,常不按规则出牌,指不定哪一天就冲向了人类生活的地球家园。面对这样的潜在威胁,我们的措施在哪里呢?让地球成为设防的星球,这是人类的共同心愿。 相似文献
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为避免传统惯性系自主定轨算法中的多次坐标转换,针对地固系分布式自主定轨算法原理及其中的关键技术开展研究。给出在地固系中进行自主星历生成的总体框图,推导了地固系自主定轨算法的基本方程,提出一种新的以地固系位置速度为状态量的状态转移矩阵解析计算方法并分析其计算量,证明了地固系自主定轨算法可以进一步降低定轨算法复杂度,且无需上注地球定向参数进行坐标转换。使用仿真数据和真实在轨测量数据的测试结果表明,提出的地固系分布式自主定轨算法与传统算法定轨精度相当,说明了所提算法的可行性,验证了星载自主定轨原型软件的有效性。 相似文献
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Robinson TD Meadows VS Crisp D Deming D A'hearn MF Charbonneau D Livengood TA Seager S Barry RK Hearty T Hewagama T Lisse CM McFadden LA Wellnitz DD 《Astrobiology》2011,11(5):393-408
The EPOXI Discovery Mission of Opportunity reused the Deep Impact flyby spacecraft to obtain spatially and temporally resolved visible photometric and moderate resolution near-infrared (NIR) spectroscopic observations of Earth. These remote observations provide a rigorous validation of whole-disk Earth model simulations used to better understand remotely detectable extrasolar planet characteristics. We have used these data to upgrade, correct, and validate the NASA Astrobiology Institute's Virtual Planetary Laboratory three-dimensional line-by-line, multiple-scattering spectral Earth model. This comprehensive model now includes specular reflectance from the ocean and explicitly includes atmospheric effects such as Rayleigh scattering, gas absorption, and temperature structure. We have used this model to generate spatially and temporally resolved synthetic spectra and images of Earth for the dates of EPOXI observation. Model parameters were varied to yield an optimum fit to the data. We found that a minimum spatial resolution of ~100 pixels on the visible disk, and four categories of water clouds, which were defined by using observed cloud positions and optical thicknesses, were needed to yield acceptable fits. The validated model provides a simultaneous fit to Earth's lightcurve, absolute brightness, and spectral data, with a root-mean-square (RMS) error of typically less than 3% for the multiwavelength lightcurves and residuals of ~10% for the absolute brightness throughout the visible and NIR spectral range. We have extended our validation into the mid-infrared by comparing the model to high spectral resolution observations of Earth from the Atmospheric Infrared Sounder, obtaining a fit with residuals of ~7% and brightness temperature errors of less than 1?K in the atmospheric window. For the purpose of understanding the observable characteristics of the distant Earth at arbitrary viewing geometry and observing cadence, our validated forward model can be used to simulate Earth's time-dependent brightness and spectral properties for wavelengths from the far ultraviolet to the far infrared. Key Words: Astrobiology-Extrasolar terrestrial planets-Habitability-Planetary science-Radiative transfer. Astrobiology 11, 393-408. 相似文献