Dual Frequency Orbiter-Radar System for the Observation of Seas and Tides on Titan: Extraterrestrial Oceanography from Satellite

Abstract

Saturn’s largest moon, Titan, is believed to have a ~100 km thick ice shell above a global ocean of liquid water. Organic materials, including liquid hydrocarbon lakes and seas in its polar terrain, cover Titan’s surface, which makes it a world of two oceans. The RADAR instrument on board Cassini, was able to probe lakes and seas during few dedicated altimetric observations, revealing its capability to work as a sounder. Herein, we describe the design of, and scientific motivation for, a dual frequency X/Ka-band radar system that is able to investigate Titan’s subsurface liquid water ocean, as well as the depth and composition of its surface liquid hydrocarbon basins. The proposed system, which could take advantage of the telecommunications dish, can operate as a sounder, as Synthetic Aperture Radar (SAR) able to map the surface at tens meters of scale resolution, and when data are acquired from close-adjacent orbits, as a repeat-pass SAR interferometer (InSAR). The instrument, which is based on the architecture of the Cassini RADAR, can also characterize Titan’s interior by using geophysical measurements of the tidal amplitude to derive high accuracy estimates of the Love number h2 from a 1500 km circular orbit.

UWB Processing Applied to Multifrequency Radar Sounders: The Case of MARSIS and Comparison With SHARAD

“…The technique here proposed has general applicability and could be helpful for the interpretation of radar data acquired by future planetary missions, for example, in the case of a multifrequency radar system for the exploration of icy moons [37] or in the context of water ice research on Mars [38].…”

Analysis of Cassini Altimetric Crossovers on Titan

“…That is, the solid tide signal is controlled over the orbit by the mean anomaly, M. Assuming a Love number h 2 = 2.5, the maximum tidal signal at the sub-Saturnian point is about 22 m when Titan is at the pericenter or apocenter (with opposite signs). Several theoretical studies have evaluated the effects of tides on Titan's surface, both solid and liquid [25], and the possibility of detecting them using radar techniques [26]. In our work, we make use of altimetric data to investigate the possibility of estimating Titan's tidal signal.…”

Validation of a Pseudospectral Time-Domain (PSTD) Planetary Radar Sounding Simulator With SHARAD Radar Sounding Data

“…Europa Clipper mission) and RIME (Radar for Icy Moon Exploration; on ESA's JUICE mission) [1]- [6], a surface clutter and volume scattering simulator is useful not only in providing insights about what the expected radar echoes or radargrams look like for discriminating clutter signals from subsurfaces, but also in aiding to develop and validate new parameter inversion algorithms [7], [8] as well as advanced processing techniques for radar sounding (e.g. clutter suppression [9] and super resolution [10], [11]).…”

“…Due to the large-scale electromagnetic scattering problems, a planetary radar sounding simulator predominantly adopts the ray tracing or facet method for the sake of efficiency, which is used to simulate cross-track clutter signals that are apparent in radargrams [3], [7], [8], [12]- [17]. Time-domain full-wave method such as Finite-Difference Time-Domain (FDTD) is an alternative for simulating subsurface and heterogenous volume scattering [18], [19].…”