Long-term Monitoring Plan of Venus using Earth-orbiting CubeSats

Venus has long been considered the twin sister of Earth due to their physical similarities, such as mass, radius, and distance from the Sun 1. This resemblance makes the comparative study between Venus and Earth important to understand an evolution turning point that caused these twin planets to be very different at present 2. Interestingly, not only Earth experiencing global warming, but also Venus is experiencing ongoing temporal changes. Long-term remote sensing observations of Venus show considerable temporal variations of Venus. Such observations were conducted using spectral intensity, polarization, and imaging measurements. They revealed variations of the SO2 gas abundance, zonal wind speeds, ultraviolet (UV) brightness, cloud top altitude, and the upper haze vertical structures above the cloud top level (~70 km altitude) 3,4,5,6,7. The main drivers of the reported variations are unclear but may be associated with surface volcanic activities, the solar cycle, or large-scale oscillations in atmospheric dynamics. To understand possible mechanisms, a long monitoring period is necessary, and reliable data calibration is mandatory. We propose a continuous monitoring project, CLOVE (Chasing the Long-term Variability of Our Nearest Neighbor Planet Venus), utilizing a combination of ground- and space-based facilities to overcome the limitations of using a single dataset. In this project, firstly, we plan a low-Earth orbit CubeSat that will monitor Venus to investigate the cloud top vertical structure, the unknown absorber(s), and the SO2 gaseous abundance, using bandpass and polarization filters at four selected wavelengths and a total 8 channels including polarization filters. We aim for our first CLOVE CubeSat to be launched in 2026. With its successful operation, we aim to proceed with the subsequent CubeSats that will continue Venus monitoring, replacing the old Sat with a new one to cover at least 15 years of time to complete one Solar Cycle. Secondly, we plan to collaborate with ground-based observation teams to perform coordinated Venus dayside observations with space-based CLOVE observations. The data will be used for cross-check validation and supplementary data to interpret our analysis. In this talk, I will explain what we have seen in the past and current data sets of Venus and the future plan with the CLOVE mission with an emphasis on polarization measurements.References1 Svedhem. H, et al., 2007: Venus as a more Earth-like planet. Nature 450, 7170, 629-6322 ORourke, J.G., Wilson, C.F., Borrelli, M.E. et al., 2023: Venus, the Planet: Introduction to the Evolution of Earths Sister Planet. Space Sci Rev 219, 103 Marcq, E. et al., 2020: Climatology of SO2 and UV absorber at Venus' cloud top from SPICAV-UV nadir dataset. Icarus 335, 1133684 Khatuntsev, I.V. et al., 2022: Twelve-Year Cycle in the Cloud Top Winds Derived from VMC/Venus Express and UVI/Akatsuki Imaging. Atmosphere 2022, 135 Lee, Y. J. et al., 2019: Long-term Variations of Venuss 365nm Albedo Observed by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope. Astronomical Journal 158:1266 Coffeen, D. L. and Hansen, J. E. 1974: Polarization Studies of Planetary Atmospheres, in Planets, Stars, and Nebulae: Studied with Photopolarimetry (Edited by T. Gehrels). University of Arizona Press, p.5187 Kawabata, K., et al., 1980: Cloud and Haze Properties from Pioneer Venus Polarimetry. Journal of Geophysical Research 85, 8129