In 2014 and 2016, the Himawari-8 and -9 satellites were launched into orbit. Owned and operated by the Japan Meteorological Agency (JMA), these satellites monitor global weather patterns and atmospheric phenomena using their multispectral Advanced Himawari Imagers (AHIs). In a recent study, a team led by the University of Tokyo presented infrared images that capture changes in Venus’ atmosphere, revealing unseen temperature patterns in its cloud tops. The results show that meteorological satellites can complement observations of Venus’ atmosphere by robotic missions and ground-based telescopes.
The team was led by Gaku Nishiyama, a visiting postdoctoral researcher at the University of Tokyo and the Institute of Space Research at the German Aerospace Center (DLR). The Max Planck Institute for Extraterrestrial Physics (MPE), National Institute of Advanced Industrial Science and Technology, the University of Tokyo’s Institute of Astronomy, Graduate School of Frontier Sciences, the National Astronomical Observatory of Japan (NAOJ), Institute of Space and Astronautical Science (ISAS) at the Japan Aerospace Exploration Agency (JAXA), the European Space Research and Technology Centre (ESTEC), and multiple universities.
Scientists have studied Venus’ atmosphere for decades, hoping to learn more about the dynamics of the hottest planet in the Solar System. However, several mysteries are still unresolved, such as its thermal tides and planetary-scale waves. As Nishiyama and his colleagues indicated in their study, multi-band spectral monitoring of Venus’ atmosphere would shed light on these and related phenomena. This presents multiple challenges, however, and robotic probes sent to Venus in the past decade have been limited to either single-band imagery or short observation periods. As Nishiyama said in a UTokyo press release:
The atmosphere of Venus has been known to exhibit year-scale variations in reflectance and wind speed; however, no planetary mission has succeeded in continuous observation for longer than 10 years due to their mission lifetimes. Ground-based observations can also contribute to long-term monitoring, but their observations generally have limitations due to the Earth’s atmosphere and sunlight during the daytime.
The Advanced Himawari Imagers measure Venus’ temperature over multiple infrared bands, showing the temporal variation across the period of observation. ©2025 Nishiyama et al. CC-BY-ND
Nishiyama and his colleagues believe meteorological satellites could fill this gap thanks to their extended lifetimes and capabilities. The Himawari satellites are scheduled to remain operational for more than a decade (until 2029). In addition, the AHI instruments provide multi-band infrared coverage of Earth’s atmosphere to obtain temperature information from different altitudes, which is essential to tracking and predicting weather patterns. Lastly, the geostationary satellites can obtain images of the turbulent atmosphere when they are aligned with Earth and Venus.
To demonstrate the potential of these missions, the team used data from the Himawari-8 and -9 satellites to map the temporal dynamics of Venus’ atmosphere and create a comparative analysis with previous datasets. This consisted of extracting all the AHI images where Venus was visible in the distance (437 images in total) to create a dataset. This allowed them to track temperature variations in multiple infrared bands in Venus’ cloud tops over time. This was then analyzed on daily and annual timescales to discern variability in Venus’ thermal tides and planetary-scale waves.
Their analysis confirmed that both the tides and waves are subject to changes in amplitude over time, which appear to decrease with altitude. Moreover, it allowed them to identify calibration discrepancies in data retrieved by previous planetary missions. Last, the results suggest that variations in thermal tide amplitude could be linked to variations in the structure of Venus’ atmosphere that occur every decade or so. However, the limited temporal resolution of the AHI data makes it very difficult to determine the physics behind these variations at this time.
Nevertheless, Nishiyama and his team believe their analysis method will provide vital data about Venus until future planetary missions are sent there. At present, there are six missions under development worldwide, including NASA’s Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERITAS) orbiter and the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) probe, and the ESA’s EnVision orbiter. In the meantime, Nishiyama and his colleagues are already contemplating how their research using multi-band spectral data from Earth observation satellites could be applied to the study of other planets:
I think that our novel approach in this study successfully opened a new avenue for long-term and multi-band monitoring of solar system bodies. This includes the moon and Mercury, which I also study at present. Their infrared spectra contain various information on physical and compositional properties of their surface, which are hints at how these rocky bodies have evolved until the present. We hope this study will enable us to assess physical and compositional properties, as well as atmospheric dynamics, and contribute to our further understanding of planetary evolution in general.
The paper that details their findings appeared in Earth, Planets and Space on June 30th.
Further Reading: University of Tokyo
