The Plasma Waves Instrument for LilacSat-3 Mission

The ionosphere is the nearest natural plasma laboratory to the Earth. Ionospheric plasma waves serve as a important diagnostic tool for understanding space plasma and space weather. The CSES 01 mission and the DEMETER satellite made in-situ measurements of low-frequency plasma waves on sun-synchronous orbits and observed a large number of wave events, including whistlers, ionospheric hiss, and artificial very low-frequency (VLF) emissions, which revealed the local response of the ionosphere to natural hazards, space weather events, and human activities such as long-distance power line harmonic radiation and high-power VLF emissions. Moreover, the propagation of low-frequency electromagnetic waves in ionospheric plasma exhibits an obvious variation with altitude. However, it is not enough to study in-situ propagation characteristics of waves at different altitudes in the mid-latitude and low-latitude ionosphere. The micro-satellite LilacSat-3 provides an opportunity for this study. LilacSat-3, a thin disk-shaped satellite with a diameter of 1 meter, developed by Harbin Institute of Technology, will be launched into a sun-synchronous orbit with a variable altitude, gradually decreasing from an initial altitude of 500 kilometers. LilacSat-3 Plasma Waves Instrument (PWI), developed by School of Space and Earth Sciences, Beihang University, incorporates a pair of concentric loops designed to measure the magnetic component of ionospheric plasma waves and ionospheric disturbance caused by ground-based artificial VLF emissions along the normal direction of the satellite disk, providing a data source for revealing the characteristics of ionospheric response to space weather events in Low Earth orbit (LEO) and studying the propagation of artificial VLF emissions. The boomless concentric loop sensors exhibit intrinsic structural compatibility with the disk-shaped satellite. PWI adopts a high-accuracy data acquisition unit with 24-bit resolution and a maximum sampling frequency up to 200kHz, and is timed by Pulse per Second (PPS) signal with an accuracy of 1μs. The operating frequency range of PWI is up to 100kHz. LilacSat-3 mission is anticipated to be launched in mid-2025.