MIT aerospace engineers have made a significant discovery highlighting the impact of greenhouse gas emissions on near-Earth space, particularly concerning the sustainability of satellite operations. This groundbreaking research, soon to be published in Nature Sustainability, reveals that the increasing levels of carbon dioxide and other greenhouse gases have the potential to alter the upper atmospheric layers, particularly the thermosphere, in ways that could dramatically reduce the number of satellites that can safely operate in low-Earth orbit in the future.
The thermosphere is a critical layer of the Earth’s atmosphere where the International Space Station and numerous satellites currently orbit. The researchers found that as greenhouse gas concentrations continue to rise, the thermosphere experiences contraction, resulting in lower atmospheric density. This decrease in density reduces atmospheric drag on satellites and space debris, which is the primary force that pulls old satellites and other debris down, allowing them to burn up upon re-entering the atmosphere.
With less atmospheric drag, the lifespans of space debris are extended, leading to increased congestion in regions of low-Earth orbit that are already experiencing high traffic. This situation poses significant risks, heightening the chances of collisions between operating satellites and the growing pool of debris. These findings have critical implications for the future of satellite operations, given that the number of satellites in low-Earth orbit has been rapidly increasing, primarily driven by the demand for broadband internet services delivered from space.
To quantitatively assess these changes, the research team conducted comprehensive simulations examining the effects of various greenhouse gas emissions scenarios on the upper atmosphere and the orbital mechanics of satellites. Their simulations predict a dramatic decrease—up to 66 percent—of the “satellite carrying capacity” in the most frequented regions of low-Earth orbit by the year 2100, largely attributable to the evolving atmospheric conditions driven by greenhouse gases.
Richard Linares, an associate professor in MIT’s Department of Aeronautics and Astronautics, emphasized the long-term implications of our present-day actions, stating that our behavior regarding greenhouse gas emissions over the last century is influencing how satellites can operate safely over the next hundred years. This assertion underscores the significant interconnectedness between our climate actions on Earth and the sustainability of outer space activities.
William Parker, the lead author of the study, further elaborated that the upper atmosphere is experiencing a fragile state due to the disruptions caused by climate change. The researchers acknowledged the remarkable increase in satellite launches in recent years, particularly focused on delivering global internet services. Without careful management of these activities and a concerted effort to reduce greenhouse gas emissions, the prospect for safe satellite operation could diminish dramatically.
The phenomenon concerning the thermosphere’s behavior is complex. It naturally expands and contracts in response to the solar cycle, which operates on an 11-year rhythm. When solar activity is low, the Earth receives less solar radiation, causing a temporary cooling and contraction of the upper atmosphere before it expands again with heightened solar activity. Historically, scientists speculated on how greenhouse gases might affect this dynamic. While these gases trap heat in the lower atmosphere, they also radiate heat away at higher altitudes, which leads to the cooling of the thermosphere.
Evidence collected over the past decade indicates changes in drag experienced by satellites, which suggest that the thermosphere is contracting due to more than just the cyclical 11-year solar variations. Parker highlighted that the changes are happening gradually but significantly, as observed by the decreased drag on various satellites over time. This contraction directly influences the operational capacity for current and future satellite missions.
Researchers noted that there are already over 10,000 satellites in low-Earth orbit, where they provide critical services such as internet connectivity, communications, navigation systems, and weather forecasting. The increasing satellite population exacerbates the need for operators to conduct regular maneuvering to avoid potential collisions. Over the last five years alone, more satellites have been launched than in the preceding six decades combined, indicating a pressing urgency to understand the sustainability of our current trajectory in satellite deployment.
To address these critical concerns, the researchers developed a method to assess the carrying capacity of low-Earth orbit by simulating different greenhouse gas emissions scenarios spanning the century ahead. They modeled how various emissions levels would influence atmospheric density and resultant drag, estimating the potential risks for satellite collisions based on the density of objects in specific altitude ranges.
The study identified “shells,” or altitude bands of interest, to model their carrying capacity—the maximum number of satellites that these specific altitude ranges can safely accommodate. They discovered that if current greenhouse gas emissions continue to rise unchecked, the satellite carrying capacity in low-Earth orbit may be severely compromised. The projections suggest that by the end of this century, the safe accommodation of satellites at altitudes between 200 and 1,000 kilometers could diminish by a striking 50 to 66 percent compared to a baseline scenario where greenhouse gas concentrations remain stable at the year 2000 levels.
This increase in orbital congestion poses the risk of creating a “runaway instability” where a cascade of collisions could produce debris that would further obstruct access to safe operating spaces for satellites. The researchers warned that without intervention, specific regions in low-Earth orbit could reach a saturation point, rendering them unusable for future satellite operations. The urgency of addressing greenhouse gas emissions is not just an environmental concern; it is a pressing issue that directly impacts the future of satellite operations.
Furthermore, the researchers established that the rise of megaconstellations—large groups of satellites like those seen with SpaceX’s Starlink—places additional pressure on the orbital environment. Given that visible saturation levels can already be detected, the investigation aimed to measure precisely how these megaconstellations could impact the overall sustainability of space. The increased frequency of launches and subsequent satellite deployments is generating a complicated dilemma for space governance, requiring a balancer to ensure that orbital space remains an accessible and functional operational venue.
Overall, this research underscores the critical intersection between aerospace operations, climate change, and sustainability. The insights gathered illustrate the urgent need for international cooperation in space traffic management. The findings serve as a clarion call for both policymakers and the aerospace community to develop strategies aimed at mitigating greenhouse gas emissions to preserve the space environment for future generations.
By addressing the challenges of greenhouse gas emissions and their pervasive effects—both terrestrial and extraterrestrial—this research points toward a tangible pathway for achieving sustainability in space exploration and satellite operations moving forward.
The authors express hope that their findings spark meaningful dialogue and decisive action toward ensuring that low-Earth orbit remains a viable and safe space for current and future satellites, as they continue to evolve to meet an increasingly digital world.
Subject of Research: Effects of greenhouse gas emissions on the satellite carrying capacity in low-Earth orbit.
Article Title: Greenhouse gases reduce the satellite carrying capacity of low Earth orbit
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