In an unexpected discovery, two weather satellites designed to monitor Earth’s atmosphere have ended up capturing valuable information about Venus.
Weather Satellites Meant for Earth Record Stunning Venus Data
Japan’s Himawari-8 and Himawari-9 satellites, launched in 2014 and 2016 respectively, were originally meant to observe storms, climate activity, and atmospheric conditions around Earth. However, for nearly a decade, they have also been quietly collecting data from the planet Venus.
These satellites are positioned in geostationary orbit, which allows them to constantly watch the same area on Earth. While their primary job is to monitor weather systems over Japan and nearby regions, they have a wide imaging range that can reach beyond Earth. This means they sometimes capture other space objects like the moon, planets, and even stars.
The discovery began by accident when scientists found images of the moon in the data from these satellites. Curious to explore further, researchers analyzed more datasets and noticed other celestial objects — including Mercury, Mars, Jupiter, and most importantly, Venus.
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This unexpected use of weather satellites as space telescopes led to a surprising outcome. Venus was visible in the satellites’ infrared images. These images allowed scientists to track variations in the light coming from Venus. Such changes can provide deep insight into the temperature and movement of the planet’s thick cloud layers.
Discovery Reveals Long-Term Temperature and Atmospheric Patterns
The Himawari-8 and Himawari-9 satellites have now created one of the longest-running sets of infrared data on Venus. These observations, collected over several years, showed small but important changes in the planet’s upper atmosphere. The data revealed signs of temperature shifts and the presence of unusual wave patterns.
Scientists identified two types of atmospheric waves in Venus’ cloud system: thermal tides and Rossby waves. Thermal tides occur when the sun heats different layers of the atmosphere, causing the air to move in wave-like patterns. Rossby waves, seen on both Earth and Venus, happen due to changes in rotation forces with latitude. These waves help move heat and air throughout the atmosphere, making them critical to understanding how a planet’s climate works.
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The weather satellites recorded how these waves change over time. For the first time, scientists could track how Rossby waves affect the temperature fields at various altitudes in Venus’ atmosphere. This kind of data is crucial for studying how Venus’ upper atmosphere behaves across many years.
This long-term information from Himawari adds to existing knowledge collected by other space missions. Notably, it complements data from the Akatsuki Venus orbiter, which carries an infrared camera known as LIR. However, researchers noticed that the LIR camera may not be providing completely accurate temperature readings.
By comparing the images taken at the same time and from the same angle, scientists found differences between what Himawari and Akatsuki’s LIR camera reported. It appears that the LIR instrument may be underestimating how much infrared radiation Venus is emitting. Thanks to the Himawari data, scientists now have a better way to recalibrate older information and improve their understanding of Venus’ climate.
Weather Satellites Open Unexpected Door for Planetary Science
One of the most surprising outcomes of this research is how Earth-observing satellites, usually focused only on weather patterns at home, have become tools for exploring other planets. Unlike dedicated planetary missions that only last a few years or cover limited areas, weather satellites like Himawari work continuously for many years. Their stable orbits and precise sensors make them ideal for long-term observation.
The Himawari satellites are especially valuable because they cover a broad range of infrared wavelengths. These wavelengths provide information about different layers of a planet’s atmosphere, from the very top down to the mid-level clouds. While planetary missions often have shorter timelines or fewer observations, Earth’s meteorological satellites are always watching and recording.
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Researchers have now stored additional images of other planets from the same satellite data and are analyzing them. These findings show that satellites originally designed to help forecast weather and track typhoons can also play a significant role in planetary science.
For nearly a decade, these two satellites have quietly monitored Venus from afar, offering an incredible bonus to science without any changes to their main mission. This discovery is a reminder that sometimes, important breakthroughs happen when we least expect them — even from tools not built for the job.
