Joint Terahertz Communication and Atmospheric Sensing in Low Earth Orbit Satellite Networks: Physical Layer Design

As the interest in the Terahertz (0.1-1THz) band grows with the technological advancements that enable communication at higher data rates, the existing use for THz-based sensing systems motivate exploration of Joint Communication and Sensing systems (JCS). Such systems can be used for the next generation of satellite constellations for the purposes of internet-backhauling, while performing scientific functions such as studying atmospheric gases. The fact that the hardware employed for both applications is highly similar, if not identical, opens the possibility of designing a new waveform that can jointly communicate and sense at the same time. In this paper, we explore Differential Absorption Radars (DAR), traditionally used for weather sensing, as a potential candidate to be operated in combination with a Chirp Spread Spectrum (CSS) modulation. We present a scenario with a satellite at Low Earth Orbit (LEO) where the CSS modulation could outperform traditional PSK modulations while making it possible to retrieve water vapor density profiles of the atmosphere with DAR. Performance of both communication and remote sensing applications are studied through simulation.