Agnirva Space Premier League - Expedition #30617: Reflecting Earth’s Light: Studying Earthshine from the ISS

Have you ever seen the dark side of the Moon faintly glowing? That ghostly glow is called Earthshine — sunlight reflected from Earth onto the Moon’s surface. From the International Space Station (ISS), scientists can measure Earthshine more precisely than ever before, thanks to a European Space Agency (ESA) experiment led by Dr. Peter Thejll of the Danish Meteorological Institute.

The Earthshine experiment aboard the ISS provides critical data about our planet’s albedo — a measure of how much sunlight Earth reflects into space. Changes in Earth’s reflectivity can affect global climate patterns, making albedo a key metric for climate science.

Traditional Earthshine measurements from ground-based telescopes often suffer from atmospheric interference. But from the vantage point of the ISS, these measurements become clearer and more accurate. Over Expeditions 69 to 73, the Earthshine instrument onboard the station observed the Moon during specific phases to quantify this subtle glow.

Why is this important? A brighter Earthshine indicates more reflective surfaces like clouds or ice, while a dimmer Earthshine could suggest increased absorption due to factors like deforestation or ocean warming. Over time, trends in Earthshine data can reveal shifts in climate systems that might otherwise go undetected.

Moreover, the ISS’s unique orbit allows for a consistent platform to observe these reflections under varying conditions — day and night cycles, different cloud covers, and seasonal changes. This continuity enhances the reliability of Earthshine data, which feeds into climate models used by researchers worldwide.

The experiment is a blend of astronomy, climatology, and satellite engineering. It also serves as an example of how creative uses of space infrastructure can yield vital information about Earth’s changing environment.

Ultimately, Earthshine isn’t just about lunar glow — it’s a mirror to our own planet’s health.

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