The outlook is promising for future long-term monitoring of planets across multiple wavelengths.
Infrared imaging data from Japan’s Himawari-8 and Himawari-9 meteorological satellites have been successfully applied to track changes in the temperature of Venus’ cloud tops over time. Led by researchers at the University of Tokyo, the team analyzed satellite images taken between 2015 and 2025 to estimate brightness temperatures across daily to yearly timescales.
Their findings reveal previously unseen temperature wave structures and highlight how meteorological satellites can offer valuable, sustained observations of Venus’ atmosphere, supplementing data from planetary missions and ground-based telescopes.
The Himawari-8 and -9 satellites, launched in 2014 and 2016, were originally designed to monitor Earth’s atmosphere using multispectral sensors called Advanced Himawari Imagers (AHIs). However, because Venus occasionally appears near the edge of these instruments’ field of view, the research team—led by visiting scientist Gaku Nishiyama—recognized an opportunity to use the AHIs for planetary observation as well.
Tracking how Venus’ cloud-top temperatures change over time is key to understanding the planet’s atmospheric behavior, including thermal tides and large-scale wave activity. Gathering long-term data for these processes, however, is challenging.
As Nishiyama noted, “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.” He added, “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.”
Long-term mission potential of meteorological satellites
Meteorological satellites offer a promising solution for continuous planetary observation, largely due to their extended operational lifespans (Himawari-8 and -9 are expected to remain active until 2029). These satellites are equipped with Advanced Himawari Imagers (AHIs), which provide multiband infrared data. This capability—still limited in many planetary missions—is essential for measuring temperature at various atmospheric layers, and the AHIs also offer frequent, low-noise observations.
To explore the potential of these satellites in Venus research, the team analyzed temporal changes in the Venusian atmosphere and compared the findings with data from previous missions.
“We believe this method will provide precious data for Venus science because there might not be any other spacecraft orbiting around Venus until the next planetary missions around 2030,” said Nishiyama.
As a first step, the researchers built a dataset by extracting all Venus-related images from the AHI records, ultimately identifying 437 usable observations. By accounting for background noise and the apparent size of Venus in each image, they were able to monitor changes in cloud-top temperatures during periods when Venus, Earth, and the satellite aligned in a favorable viewing configuration.
Wave patterns and atmospheric changes detected
The retrieved temporal variations in brightness temperatures were then analyzed on both year and day scales and compared for all infrared bands to investigate variability of thermal tides and planetary-scale waves. Variation in thermal tide amplitude was confirmed from the obtained dataset. The results also confirmed a change in amplitude of planetary waves in the atmosphere with time, appearing to decrease with altitude.
While definitive conclusions on the physics behind the detected variations were challenging due to the limited temporal resolution of the AHI data, variations in the thermal tide amplitude appeared to be possibly linked to decadal variations in the Venus atmosphere structure.
In addition to successfully applying the Himawari data to planetary observations, the team was further able to use the data to identify calibration discrepancies in data from previous planetary missions.
Nishiyama is already looking at implications of the study beyond Venus’ horizon. “I think that our novel approach in this study successfully opened a new avenue for long-term and multiband 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.”
The prospect of accessing a range of geometric conditions untethered from the limitations of ground-based observations is clearly an exciting one. “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.”
Reference: “Temporal variation in the cloud-top temperature of Venus revealed by meteorological satellites” by Gaku Nishiyama, Yudai Yudai, Shinsuke Uno, Shohei Aoki, Tatsuro Iwanaka, Takeshi Imamura, Yuka Fujii, Thomas G. Müller, Makoto Taguchi, Toru Kouyama, Océane Barraud, Mario D’Amore, Jörn Helbert, Solmaz Adeli and Harald Hiesinger, 30 June 2025, Earth, Planets and Space.
DOI: 10.1186/s40623-025-02223-8
Funding: This work was supported by JSPS KAKENHI Grant Number JP22K21344, 23H00150, and 23H01249, and JSPS Overseas Research Fellowship.
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