Utilizing small satellites for improved gravity science of icy moons

Abstract:

Measurement of a celestial body's gravity field provides fundamental information on the body's internal structure including mass distribution, tectonic process and thermal evolution. Prior gravity science experiments have enabled the development of gravity field models of various bodies such as Mars, Mercury, Jupiter, Europa, Saturn, Titan and Enceladus. Over the past decade, there has been growing interest in developing mission concepts designed to explore the icy satellites of the gas giants Jupiter and Saturn, some of which harbor a subsurface ocean and are geologically active, such as Europa, Enceladus and Titan. While the Galileo and Cassini missions provided data that helped improve our understanding of these bodies, these missions were not dedicated for icy moons exploration and hence many questions were left unanswered. These bodies are complex and less understood than terrestrial planets and have unique features of their own with Europa's widely distributed and visible cracks and streaks; geological activity in the form active plumes at Enceladus and thick atmosphere and smooth surface at Titan. In addition, the presence of an ocean makes these bodies key destinations in the search for life elsewhere in the Solar System. While gravity science alone cannot constrain the interior models due to its non-uniqueness, gravity data combined with additional measurement data such as altimetry and topography mapping can provide a better understanding of these complex worlds and their interactions with their parent planet. This study investigates the use of small satellites to conduct gravity science of icy moons that can complement larger flagship missions like Europa Clipper and enable high-risk high-reward science opportunities. Using scaled down science requirements from previously studied icy moons mission concepts in the 2013-2022 Planetary Science Decadal Survey, focus will be given on the relative accuracy of recovering spherical harmonic gravity coefficients, which are highly dependent on precise orbit determination. Simulated results from flybys, single orbiters and multi-orbiter mission scenarios will be presented along with a technology road map necessary to meet various levels of science return.