PIONEERS: a 6DoF motion sensor to measure rotation and tides in the Solar System

Abstract

AbstractObservation 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 $${2}\,\upmu \textrm{rad}\, \textrm{s}^{-1} \textrm{H}\textrm{z}^{-1/2}$$ 2 μ rad s - 1 H z - 1 / 2 and $${20}\,\upmu \textrm{m}\,\textrm{s}^{-2} \textrm{H}\textrm{z}^{-1/2}$$ 20 μ m s - 2 H z - 1 / 2 respectively in its compact version and three orders of magnitude better ($${5}\,\textrm{nrad}\, \textrm{s}^{-1} \textrm{H}\textrm{z}^{-1/2}$$ 5 nrad s - 1 H z - 1 / 2 and $${10}\,\textrm{pm}\,\textrm{s}^{-2} \textrm{H}\textrm{z}^{-1/2}$$ 10 pm s - 2 H 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