Space debris, including defunct satellites and leftover rocket stages, poses an increasing risk to operational spacecraft and human space missions. Recent research indicates that heightened solar activity may accelerate the descent of space debris, influencing how scientists estimate satellite lifespans and collision probabilities.
Low Earth Orbit (LEO), ranging from 400 to 2,000 km, serves as a prime location for image surveillance satellites, including Starlink and large-scale internet “megaconstellations.”
However, this region is cluttered with “space junk,” like retired satellites and rocket stages, posing risks to new launches. A single collision can trigger a chain reaction of extensive damage.
Efforts to use robotic systems for capturing space debris are still in their infancy. Researchers are currently focused on accurately tracking debris and identifying the most hazardous objects for future removal.
“We demonstrate that heightened solar activity accelerates the altitude loss of space debris surrounding Earth,” explained Dr. Aisha Ashraf, a researcher at the Vikram Sarabhai Space Center.
“For the first time, we reveal that this altitude reduction occurs significantly faster once solar activity surpasses a specific threshold.”
“This finding is expected to play a crucial role in planning sustainable future space operations.”
The sun operates on an 11-year cycle, alternating between active and quiet phases, which correlates with sunspot numbers and affects the intensity of solar radiation.
UV radiation and charged particles (such as helium nuclei and heavy ions) increase during active periods.
When this solar outburst peaks, as observed in 2024, it heats Earth’s thermosphere, located at altitudes of 100 to 1,000 km, with temperatures ranging from 500 to 2,500 degrees Celsius.
This elevation in atmospheric density around orbiting objects (350-36,000 km altitude) increases atmospheric resistance or “drag,” accelerating their descent.
In their study, Dr. Ashraf and colleagues analyzed the historical trajectories of 17 LEO space debris objects over a 36-year timeline beginning in the 1960s, encompassing the 22nd to 24th solar cycles.
These objects orbit the Earth every 90 to 120 minutes at altitudes of 600 to 800 km and have yet to reenter the atmosphere; eventually, they will combust upon reentry.
Since space debris does not engage in active station-keeping like artificial satellites, its descent rates are influenced solely by variations in thermosphere density.
“This characteristic makes space junk an excellent indicator for assessing the long-term impacts of solar activity on atmospheric drag,” stated the researchers.
They correlated these orbits with extensive data from the German Geoscience Research Center, which monitors sunspot activity alongside daily shifts in solar radio and extreme ultraviolet (EUV) radiation.
The findings indicated that when sunspot numbers exceed two-thirds of their peak, space debris crosses a “transition boundary,” prompting faster descent.
“This threshold appears unrelated to a specific solar radiation value but rather hinges on the sun’s proximity to its peak activity,” remarked Dr. Ashraf.
“At this juncture, the sun emits more intense EUV radiation, potentially due to amplified solar activities near the peak.”
The researchers emphasized that their discoveries will assist space scientists in optimizing satellite trajectories and mitigating collision risks with debris.
“Our findings suggest that when solar activity heightens beyond a particular level, satellites decline in altitude more rapidly, akin to space debris, necessitating more frequent orbital adjustments,” Dr. Ashraf noted.
“This directly impacts a satellite’s operational duration in orbit and its fuel requirements, particularly for missions launched close to solar maximum.”
“Remarkably, all this valuable information derives from objects launched in the 1960s.”
“They continue to contribute to our understanding and act as vital instruments for investigating the long-term effects of solar activity on the thermosphere.”
The team’s study has been published in the latest issue of Frontiers in Astronomy and Space Science.
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Aisha M. Ashraf et al. 2026. Characterizing the influence of solar cycles on long-term orbital degradation of Low-Earth Orbit space debris. Front. Astron. Space Sci. 13; doi: 10.3389/fspas.2026.1797886
Source: www.sci.news
