Abstract

Observation of rotation variations and tides provides constraints on the interior properties of celestial bodies. Both can be precisely measured with a 6DoF (Degrees of Freedom) motion sensor placed on their surface. This type of instrument measures rotation rates and linear accelerations in a large frequency band, which includes the frequencies involved in the tides and rotation variations. A novel sensor under development aims to measure rates and accelerations with an amplitude spectral density of \({2}\,\upmu \textrm{rad}\, \textrm{s}^{-1} \textrm{H}\textrm{z}^{-1/2}\) and \({20}\,\upmu \textrm{m}\,\textrm{s}^{-2} \textrm{H}\textrm{z}^{-1/2}\) respectively in its compact version and three orders of magnitude better ( \({5}\,\textrm{nrad}\, \textrm{s}^{-1} \textrm{H}\textrm{z}^{-1/2}\) and \({10}\,\textrm{pm}\,\textrm{s}^{-2} \textrm{H}\textrm{z}^{-1/2}\) , respectively) with its high-performance version. Here, we compare these instrument performances with the precision required to measure rotation and tides in order to improve our knowledge of the interior of nine celestial bodies identified as targets for future space missions: Dimorphos, Phobos, Europa, Io, Titan, Enceladus, Triton, the Moon and Mars. Results indicate that Phobos, the Moon, and Mars cannot be investigated with the compact model, but that the interior of the other bodies can be constrained through measurements of rotation rate, and/or centrifugal acceleration, and/or tidal acceleration. We also find that the high-performance prototype instrument is suitable for acceleration measurements for all nine bodies, but not adequate for inferring interior constraints from rotation rate measurements for Triton, the Moon, and Mars. The signatures of the interior in the rotation rate and centrifugal and tidal accelerations also provide scientific requirements for future developments of 6DoF motion sensors for these nine bodies.

Graphical Abstract

中文翻译：

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PIONEERS：用于测量太阳系旋转和潮汐的 6DoF 运动传感器

摘要

自转变化和潮汐的观测为天体的内部特性提供了限制。两者都可以通过放置在其表面的 6DoF（自由度）运动传感器进行精确测量。此类仪器可测量大频带内的旋转速率和线性加速度，其中包括潮汐和旋转变化所涉及的频率。正在开发的新型传感器旨在测量幅度谱密度为\({2}\,\upmu \textrm{rad}\, \textrm{s}^{-1} \textrm{H}\textrm 的速率和加速度{z}^{-1/2}\)和\({20}\,\upmu \textrm{m}\,\textrm{s}^{-2} \textrm{H}\textrm{z}^ {-1/2}\)分别以其紧凑版本和三个数量级更好 ( \({5}\,\textrm{nrad}\, \textrm{s}^{-1} \textrm{H}\ textrm{z}^{-1/2}\)和\({10}\,\textrm{pm}\,\textrm{s}^{-2} \textrm{H}\textrm{z}^{ -1/2}\)，分别）及其高性能版本。在这里，我们将这些仪器性能与测量旋转和潮汐所需的精度进行比较，以提高我们对被确定为未来太空任务目标的九个天体内部的了解：Dimorphos、Phobos、Europa、Io、Titan、Enceladus、Triton 、月球和火星。结果表明，火卫一、月球和火星无法使用紧凑模型进行研究，但可以通过测量旋转速率、和/或离心加速度、和/或潮汐加速度来约束其他天体的内部。我们还发现，高性能原型仪器适用于所有九个天体的加速度测量，但不足以根据海卫一、月球和火星的旋转速率测量推断内部约束。内部的旋转速率、离心加速度和潮汐加速度特征也为这九个物体的 6DoF 运动传感器的未来开发提供了科学要求。

图形概要