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Synergistic Science at the Jovian Icy Moons with RIME and REASON

Presentation #315.01 in the session Icy Satellites: Surfaces, Ice Shell, and Interior (Poster)

Published onOct 23, 2023
Synergistic Science at the Jovian Icy Moons with RIME and REASON

Introduction

The Jovian system hosts three of the largest icy bodies in the solar system: Europa, Ganymede and Callisto. ESA’s JUICE and NASA’s Europa Clipper missions are set to explore these icy worlds concurrently within the next decade. Both missions are equipped with radar sounders, namely the Radar for Icy Moons Exploration (RIME) on JUICE and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) on Europa Clipper. RIME operates with a 9 MHz center frequency and a 1-MHz or 3-MHz bandwidth (noted [9/1 MHz] and [9/3 MHz], respectively). REASON is a dual-frequency radar sounder at [60/10 MHz] and [9/1 MHz]. Combining the multi-frequency and multi-bandwidth capabilities of both radars provides observations uniquely suited for investigating the near-surface and subsurface properties (and also potentially the magnetospheric plasma environment) of these icy moons.

Combined 9-MHz radiometry dataset

Radar signals transmitted and recorded back at the antenna hold insights into the surface and subsurface properties such as roughness, porosity, temperature, or brine content encountered along its propagation path. Merging the 9-MHz radiometry between RIME and REASON would effectively produce a relatively calibrated homogeneous dataset to enable comparative studies of such properties between the icy Galilean moons. Relative calibration could be performed at crossovers and/or along contiguous ground tracks. Using the Jovian decametric cyclotron emissions as a reference signal can also be considered.

Ice properties from multi-frequency observations

The geometric scale of dielectric gradients responsible for signal scattering is a function of its frequency. Combining multi-frequency observations from RIME and REASON offers the possibility to characterize the ice at different scales, thereby further constraining their statistical geometry. Again, observations at crossovers are preferred for these comparisons to be optimal.

Ice properties from multi-bandwidth observations

The radar surface reflectance of icy environments is mainly a function of roughness and regolith porosity. However, sharp layering (e.g., lag deposits or refrozen brines) within the near-surface (i.e., depths < vertical resolution) can also strongly modulate the signal. Near-surface layering is challenging to deconvolve from other surface properties. However, the strength ratio of multi-bandwidth reflections centered at the same frequency (9 MHz) could constrain the effects of surface roughness to better characterize near-surface layering representing bulk heterogeneity of the icy regolith.

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