A new study suggests that the Sun may play a larger role in cleaning up low Earth orbit than previously measured. By examining decades of orbital data, researchers found that periods of stronger solar activity are closely linked to faster reentry rates for space debris.
The finding arrives as Earth’s orbital environment becomes more congested with satellites and inactive objects. While orbital decay has long been associated with changes in solar conditions, the latest research focuses on the long-term behavior of debris rather than short operational windows.
Researchers from the Vikram Sarabhai Space Centre and the Indian Institute of Space Science and Technology analyzed historical orbital records to better understand what drives natural reentry processes. Their work, published in Frontiers in Astronomy and Space Sciences, examined how multiple solar cycles influenced objects already in orbit.
Four Solar Cycles Reveal A Persistent Pattern
According to the study in Frontiers in Astronomy and Space Sciences, researchers tracked 17 space objects across nearly four decades. The observation period extended across solar cycles 22, 23, 24 and into cycle 25.
Solar cycles are periods of changing solar activity that occur from one maximum to the next, roughly every 11 years. During active phases, sunspot numbers rise and solar emissions intensify.
To build the dataset, the researchers began with95 candidate objects selected from the Space-Track catalog maintained through North American Aerospace Defense Command (NORAD). From there, they narrowed the sample to debris suitable for long-term analysis. Among the tracked objects was Explorer 7, one of the oldest entries included in the catalog and identified with catalog number 22.
The researchers noted that debris offered a more reliable way to study natural orbital decay than active satellites, which frequently counter atmospheric effects through onboard systems.
Extreme Ultraviolet Radiation Stood Apart
The strongest effect identified in the study came from extreme ultraviolet radiation (EUV). As explained by the researchers, while the influence of solar activity on satellite drag has long been recognized, its long-term role in the orbital decay of space debris has remained insufficiently explored.
“The rapid expansion of the space sector and the corresponding growth in space debris population have made it increasingly important to understand the long-term drivers of orbital decay,” they added.
The study found that geomagnetic activity played a smaller role in orbital decay than EUV radiation. To better understand these effects, researchers compared their findings with solar observations collected by the joint NASA–ESA SOHO mission. Operating continuously since 1996, SOHO provided part of the reference data used in the study.
Growing Orbital Traffic Boosts Decay Research
The study connects directly to concerns about congestion in low Earth orbit. As stated in the source material, operational spacecraft and inhabited stations already adapt to changing orbital conditions. Both the International Space Station and Tiangong perform routine maneuvers to reduce collision risks linked to debris.
The broader environment has also changed with the expansion of large satellite constellations. The source reports that SpaceX Starlink completed more than 50,000 collision avoidance maneuvers during the first half of 2024 to maintain safe operations.
As more satellites are launched and more debris accumulates, tracking the connection between solar activity and atmospheric drag is becoming an increasingly relevant part of managing the space environment.
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