[P-PS01] Outer Solar System Exploration Today, and Tomorrow

[PPS01-P04] Status update of seismometer package for Dragonfly relocatable lander

*Hiroaki Shiraishi¹, Takefumi Mitani¹, Satoshi Tanaka¹, Taichi Kawamura³, Keisuke Onodera², Ryuhei Yamada⁴, Hideki Murakami⁹, Shunichi Kamata⁵, Jun Kimura⁶, Hiroyuki Kurokawa⁷, Kiwamu Nishida², Yasuhito Sekine⁸, Takeshi Tsuji¹⁰, Ralph Lorenz¹¹ (1.Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, 2.Earthquake Research Institute / The University of Tokyo, 3.Universite Paris Cite Institut de physique du globe de Paris CNRS, 4.The University of Aizu, Revitalization and Creation Support Center, 5.Faculty of Science, Hokkaido University, 6.Osaka University, 7.The University of Tokyo, 8.Earth-Life Science Insitute, Tokyo Institute of Technology, 9.Kochi University, 10.Department of Systems Innovation, the University of Tokyo, 11.Johns Hopkins University Applied Physics Laboratory)

Keywords:Titan, Seismometer, Cryogenic, Internal Structure

Dragonfly is a relocatable lander that would use dual-quad rotors to perform soft-landings at multiple sites on the Saturn’s largest moon, Titan. The spacecraft will be launched in 2028 and explore Titan for ~3 years in the mid-2030s. The Geophysical and Meteorological package (“DraGMet”) onboard Dragonfly is a suite of sensors to monitor the Titan surface/subsurface environment. It includes a single-axis (vertical) sensitive seismometer, as well as two sets of small geophones, which are installed on the lander skids, together with temperature and pressure sensors, anemometer for wind speed/direction, measurement of thermal/electrical properties of surface material, and methane and hydrogen sensors. According to the current scenario, the seismometer will be lowered to sit on the ground by a winch at each landing site and protected from the wind loads using a pseudo-streamlined shield. During the seismic observation, the above-mentioned meteorological sensors should be simultaneously operated.
In these years, a series of laboratory/field tests have been conducting using qualified seismometer models with their proximity electronics, or preamplifier circuits. During these tests, a temperature dependence of sensor characteristic and its performance to measure natural ground motion (what is called ‘microseism’) were investigated at a tunnel of the domestic seismic observatory and/or inside a pressurized cryogenic chamber. The tolerance of Titan’s environment, where the surface would be extremely cold at 94 Kelvin, has been confirmed and several key parameters are clarified to design the flight model of seismometer package. The engineering models of seismometer package are fabricated and their environmental tests for space flight are currently conducted. As the next step, the whole assembly for DraGMet sensor suites and their mechanical/electrical tests will be done. And also, a field test to simulate the Titan's atmospheric conditions is planned to investigate the effect of wind shiled cover/winch tether on seismic observation. In this paper, the outline of seismic experiment on Titan and the ground test results of seismometer package will be presented.