Design of the PRELUDE CubeSat for investigating ionospheric D-region earthquake precursor

Despite advances in satellite remote sensing, predicting large earthquakes, remains a significant challenge due to the unpredictable nature of these events. To address this challenge, our study, building upon the achievements of the French DEMETER satellite, focuses on atmospheric and space electrical variations as potential indicators of ionospheric D-region precursors to earthquakes. This approach is expected to contribute to the enhancement of short-term prediction capabilities. For this purpose, we would like to introduce our CubeSat PRELUDE (Precursory electric field observation CubeSat Demonstrator), a tiny satellite dedicated to the earthquake precursor detection and elucidated the physical mechanism. PRELUDE is scheduled for launch in JFY2025 as part of JAXA’s Innovative Satellite Technology Demonstration Program. This study presents the results of the system design, development, and mission planning of the PRELUDE, aimed at clarifying the physical mechanisms behind the statistically significant earthquake precursor ionospheric phenomena. PRELUDE is a 6U CubeSat specialized in VLF electromagnetic wave intensity observation, weighing 8 kg. To achieve miniaturization, it incorporates a drive recording function to downlink only the data surrounding the EQ epicenter to ground stations, reducing data storage and transmission requirements. Additionally, it hybridizes the Langmuir and electric field probes, typically found on satellites weighing over 100 kg like DEMETER, into a compact design suitable for CubeSats weighing just a few kilograms. The hybrid sensor unit extends booms bidirectionally by 1.5 m from the satellite using a folding extension mechanism, In this presentation, we show the satellite design requirements for elucidating the mechanism of earthquake precursor phenomena.