标题： 金星的极运动 显示英文标题

标题： Polar motion of Venus

摘要： 五次金星任务正在开发中，以在十年内研究这颗行星，其中美国宇航局的VERITAS和欧洲航天局的EnVision任务都包括地质物理调查作为其目标之一。 它们的雷达和重力实验将确定金星的方向，从而分析其自转动力学，以推断相关的地质物理和大气特性。 这项工作旨在表征金星的极运动，定义为在其固体内框架中自转轴的运动。 我们专注于其内部和大气层的特征，以支持未来轨道器对极运动的潜在探测。 我们开发了一个三轴行星的极运动模型，考虑了太阳力矩、粘弹性地幔的离心和潮汐形变以及大气动力学。 核心-地幔耦合效应被单独分析，考虑了一个简化的球形核心。 我们计算了自由运动的周期和阻尼时间（即切萨雷摆动），并确定了强制运动的频率和振幅。 我们重新审视了切萨雷频率表达式。 太阳力矩是影响金星切萨雷频率的主要现象，使其增加2.75倍。 我们的模型预测切萨雷周期范围为[12900; 18900]年。 在EnVision的4年主要任务期间，切萨雷摆动在金星表面表现为约90米的线性极漂移，处于其分辨率的极限。 我们还预测了由大气和太阳力矩驱动的强制极运动振荡，振幅约为20米。 与在这段时间内在惯性空间发生的240米自转轴进动相比，这些结果表明，金星的极运动也可能被未来的轨道器探测到。 在预期这些任务时，应将极运动纳入旋转模型中，为金星的内部结构提供额外的约束。 显示英文摘要

摘要： Five Venus missions are under development to study the planet in the next decade, with both NASA's VERITAS and ESA's EnVision featuring a geophysical investigation among their objectives. Their radar and gravity experiments will determine Venus's orientation, enabling analyses of its spin dynamics to infer relevant geophysical and atmospheric properties. This work aims to characterize Venus's polar motion, defined as the motion of its spin axis in a body-fixed frame. We focus on signatures from its interior and atmosphere to support potential detections of polar motion by future orbiters. We developed a polar motion model for a triaxial planet accounting for solar torque, centrifugal and tidal deformations of a viscoelastic mantle, and atmospheric dynamics. Core-mantle coupling effects were analyzed separately, considering a simplified spherical core. We computed the period and damping time of the free motion (i.e., the Chandler wobble) and determined the frequencies and amplitudes of the forced motion. We revisited the Chandler frequency expression. Solar torque is the dominant phenomenon affecting Venus's Chandler frequency, increasing it by a factor of 2.75. Our model predicts a Chandler period in the range [12900 ; 18900] years. The Chandler wobble appears as a linear polar drift of about 90 meters on Venus's surface during EnVision's 4-year primary mission, at the limit of its resolution. We also predict forced polar motion oscillations with an amplitude of about 20 meters, driven by the atmosphere and the solar torque. Compared to the 240 meter spin axis precession occurring in inertial space over this duration, these results suggest that Venus's polar motion could also be detectable by future orbiters. Polar motion should be incorporated into rotation models when anticipating these missions, providing additional constraints on the interior structure of Venus.