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arXiv 0812.1485gr-qcastro-phphysics.space-ph
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朱诺、木星的angular momentum和透镜-瑟林效应

Juno, the angular momentum of Jupiter and the Lense-Thirring effect

Lorenzo Iorio

摘要:

最近批准的朱诺号任务将在一个高偏心率(r_min=1.06R_Jup,r_max=39R_Jup)的极轨道(i=90度)上绕木星运行一年,以准确地绘制木星的磁场和引力场等。这样的轨道配置产生了一个理想的情况,在原则上,试图通过朱诺节点欧米茄的广义相对论的透镜-Thirring效应的测量将被移动约570米,在任务的持续时间。相反地,假设广义相对论是正确的,所提出的测试可以被视为对木星角动量S的直接、动态测量,这将提供关于这颗巨行星内部结构和形成的重要信息。木星引力位多极展开的带谐系数J_L,L= 2,3,4,6引起的长周期轨道摄动是系统偏差的主要来源。虽然Lense-Thirring节点速率与倾角i无关,但当i=90时,节点纬向扰动消失。事实上,轨道注入误差将导致δi偏离理想的极坐标几何,因此尽管朱诺号预计会改善低度纬向扰动,但纬向扰动仍将以不可接受的高水平发挥作用。ω、近木星ω和平均距平M的线性组合抵消了J_2和J_6的影响。为了将它们对相对论信号的偏差降低到百分比水平,需要在未取消的J_3和J_4中改进两个数量级;这似乎并不不现实,因为在这样的环带中期望的改进水平是三个数量级。

英文摘要:

The recently approved Juno mission will orbit Jupiter for one year in a highly eccentric (r_min=1.06R_Jup, r_max=39R_Jup) polar orbit (i=90 deg) to accurately map, among other things, the jovian magnetic and gravitational fields. Such an orbital configuration yields an ideal situation, in principle, to attempt a measurement of the general relativistic Lense-Thirring effect through the Juno's node Omega which would be displaced by about 570 m over the mission's duration. Conversely, by assuming the validity of general relativity, the proposed test can be viewed as a direct, dynamical measurement of the Jupiter's angular momentum S which would give important information concerning the internal structure and formation of the giant planet. The long-period orbital perturbations due to the zonal harmonic coefficients J_L, L=2,3,4,6 of the multipolar expansion of the jovian gravitational potential accounting for its departures from spherical symmetry are a major source of systematic bias. While the Lense-Thirring node rate is independent of the inclination i, the node zonal perturbations vanish for i=90. In reality, the orbit injection errors will induce departures δi from the ideal polar geometry, so that the zonal perturbations will come into play at an unacceptably high level, in spite of the expected improvements in the low-degree zonals by Juno. A linear combination of Omega, the periJove omega and the mean anomaly M cancels out the impact of J_2 and J_6. A two orders of magnitude improvement in the uncanceled J_3 and J_4 would be needed to reduce their bias on the relativistic signal to the percent level; it does not seem unrealistic because the expected level of improvement in such zonals is three orders of magnitude.

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