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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The size, shape and orientation of the asteroid Vesta based on data from the Dawn mission
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The size, shape and orientation of the asteroid Vesta based on data from the Dawn mission

机译：基于黎明任务的数据的小行星Vesta的大小，形状和方向

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摘要

The aim of this paper is to study the size, shape, and orientation of the asteroid Vesta based on the Dawn spacecraft observations. In this line, three main reference surfaces are defined; the geoid, reference ellipsoid, and best-fit ellipsoid. To be consistent with International Astronomical Union (IAU) standards, all the computations are done in the Claudia Double-Prime coordinate system. The geoid and its potential value W-0 are computed by fitting an equipotential surface to the shape of Vesta in a least squares sense regarding the topographic bias effect. We find that the topographic bias effect on the geoid potential value as well as the geoidal and topographic heights is significant. The geoid potential value Wo is estimated equal to 68709 24 m(2)/s(2). The reference ellipsoid is defined as an equipotential ellipsoid which best fits the geoid. The reference ellipsoid is computed based on the fundamental geodetic constants which define a geodetic reference system (GRS). The semi-axes of the triaxial reference ellipsoid are found to be equal to 280413 +/- 104 m, 274572 +/- 102 m, and 231253 +/- 86 m with the equatorial semi major axis longitude 8.29 degrees E, while the semi-axes of the biaxial reference ellipsoid are 278556 +/- 117 m and 229921 +/- 76 m. The results show that the geoidal heights with respect to the triaxial reference ellipsoid are significantly different from the geoidal heights with respect to the biaxial reference ellipsoid. The parameters of the best-fit ellipsoid are estimated by fitting geometrical ellipsoids with various degrees of freedom to Vesta's shape in a least-squares sense. We report the semi-axes of the general best-fit ellipsoid with 9 degrees of freedom equal to 284562 +/- 75 m, 277248 73 m, and 226405 57 m. Regarding the orientation of Vesta, we find that the angle between the equatorial semi-major axis of the general best-fit ellipsoid and the X-axis of the coordinate system is 9.17 degrees +/- 0.47, and the angle between its polar axis and the Z-axis is equal to 0.63 degrees +/- 0.05. Furthermore, the spherical harmonic coefficients of the shape model of Vesta up to degree 180 are computed, giving the ability to estimate the parameters of the general best-fit ellipsoid. The significant differences observed between the parameters of the general best-fit ellipsoid derived from the spherical harmonic coefficients of the shape model, and those derived from the fitting are due to the large polar and equatorial flattenings of Vesta. We estimate that the offset of the center of figure from the center of mass is 1350 +/- 53 m, and the mean radius of Vesta is 261403 +/- 39 m. (C) 2017 Elsevier B.V. All rights reserved.
机译：本文的目的是研究根据黎明航天器观察的小行星Vesta的尺寸，形状和定向。在这一行中，定义了三个主要参考表面;大石波，参考椭圆体和最适合椭球。符合国际天文联盟（IAU）标准，所有计算都在克劳迪娅双重坐标系中完成。通过将等电位表面拟合到Vesta的形状，在关于地形偏差效应的最小方形意义上的vesta的形状来计算地偶像和其电位值W-0。我们发现地形偏差对大地幂势值以及大流量和地形高度都很重要。大量地电位值Wo估计等于68709 24 m（2）/ s（2）。参考椭圆体定义为能够适合大型木质的等电位椭圆体。基于基本的大地测量常数来计算参考椭圆体，其定义了大地测量参考系统（GRS）。发现三轴参考椭圆体的半轴等于280413 +/- 104 m，274572 +/- 102 m和231253 +/- 86 m，赤道半主轴经度8.29°e，半双轴参考椭圆体的-AXES为278556 +/- 117 m和229921 +/- 76米。结果表明，相对于三轴参考椭球相对于双轴高度相对于双轴参考椭球显着不同。通过在最小二乘意义上用不同程度的自由度拟合几何椭圆体来估计最佳椭圆体的参数。我们报告了一般最佳椭圆体的半轴，具有9度自由等于284562 +/- 75 m，277248 73 m和226405 57 m。关于Vesta的取向，我们发现一般最佳拟合椭球和坐标系的x轴之间的赤道半主轴之间的角度为9.17度+/- 0.47，其极轴和轴之间的角度Z轴等于0.63度+/- 0.05。此外，计算VESTA的形状模型的球形谐波系数，高达180度，估计一般最佳椭圆体的参数的能力。源于形状模型的球形谐波系数的一般最佳椭圆体的参数之间观察到的显着差异，以及源于拟合的那些是Vesta的极性和赤道扁平。我们估计从质心的中心的中心的偏移是1350 +/- 53米，Vesta的平均半径为261403 +/- 39米。 （c）2017年Elsevier B.V.保留所有权利。

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