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

Marco Mastrogiuseppe

doi:10.3390/rs11161898

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.

Highlights

Titan, the second largest moon in our solar system, has been repeatedly observed by the Cassini spacecraft during its 13 years exploration of the Saturnian system (2004–2017)
The Cassini RADAR instrument was capable of operating in multimode as a Synthetic Aperture Radar (SAR) for surface imaging, as a radar altimeter for topography measurements, as a scatterometer for surface composition and, in passive mode, as a radiometer for brightness temperature [1]
Hundred meters high dunes fields [2], which are spread across the equator (±30◦ in latitude), covering about 15% of the whole surface [3,4] have been observed by the instruments in different modes (i.e., SAR, altimetry, radiometry)

Summary

Introduction

The second largest moon in our solar system, has been repeatedly observed by the Cassini spacecraft during its 13 years exploration of the Saturnian system (2004–2017). Hundred meters high dunes fields [2], which are spread across the equator (±30◦ in latitude), covering about 15% of the whole surface [3,4] have been observed by the instruments in different modes (i.e., SAR, altimetry, radiometry) Their shape is believed to be the result of a general eastward transport of cohesive organic solids [5], their morphology being similar to the terrestrial dunes seen in Namib, Sahara, and Arabian deserts [6], and their material is likely to be composed by solid hydrocarbons, mixed with water ice at interdune [7,8,9,10]. Their formation is still the object of studies, some hypothesis regarding their endogenic origin has been recently proposed [20]

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