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To address the rapidly evolving space environment and ensure its preservation for future generations, NASA has released the first part of its integrated Space Sustainability Strategy. This marks a pivotal step in advancing NASA’s leadership in this critical global issue, as the agency recognizes the growing challenges posed by the increasing activity in space.
NASA defines space sustainability as the ability to maintain safe, peaceful, and responsible space activities indefinitely, while preserving the outer space environment for future generations. This involves meeting current needs without compromising the long-term health of space operations. Over the years, NASA has consistently been a leader in fostering responsible space practices. The Agency’s best practices, models, and technologies have been widely adopted, establishing NASA as a global leader in space sustainability. However, the space environment is rapidly changing, and the increasing number of operational satellites, especially in low Earth orbit (LEO), has contributed to the growing issue of space debris.
NASA’s strategy divides space sustainability into four operational domains: Earth, Earth orbit, cislunar space (the area near the Moon) including the Lagrange points, and deep space, including other celestial bodies. The first volume of the strategy addresses sustainability in Earth orbit, with plans to release additional volumes focusing on the other domains. Low Earth orbit (LEO), the focus of volume one of NASA’s Space Sustainability Strategy, is the most densely populated region for orbital debris. As space becomes more crowded with satellites and other space activities, the risks of collisions and debris generation increase.
Emerging technologies such as satellite constellations for LEO communications, satellite servicing, and in-space manufacturing are reshaping the space landscape. Furthermore, the increase in lunar and Mars missions presents new challenges for sustainable operations in these regions.
The expansion of space activities demands careful attention to sustainability, as space debris and micrometeoroid risks pose a significant threat to human spaceflight, including missions to the International Space Station (ISS) and NASA’s Artemis Program. Sustainability is critical to ensuring the long-term viability of space exploration and the safety of astronauts and robotic missions.
“The release of this strategy represents significant progress for NASA on space sustainability,” said NASA Deputy Administrator Pam Melroy. “Space is becoming more congested, and it’s only going to get busier. To ensure that space remains usable for future generations, it’s crucial that we act now. NASA is committed to aligning its resources to support sustainable space activities both now and in the future.”
Earth orbit, particularly in Low Earth Orbit (LEO), presents significant and highly visible challenges to space sustainability. This domain encompasses a range of critical topics such as space situational awareness, space traffic coordination, space environment (weather) awareness, orbital debris management, and spacecraft servicing. A key focus of this domain is ensuring the health and safety of human spaceflight operations.
Humanity’s growing activities in Earth’s orbit have highlighted the risks associated with space operations, yet awareness of these risks has lagged behind. Space situational awareness (SSA) has been recognized since the beginning of the space age, with attention focused on tracking active spacecraft. However, only in recent years has the potential for collisions and the increasing volume of orbital debris received more attention. Orbital debris, first recognized in 1961, became a key concern by the late 1970s, and as space traffic grew, space traffic coordination (STC) emerged as an important issue. The effects of space operations on scientific measurements, such as those of Earth’s ionosphere and exoplanets, are now starting to be recognized as a challenge in the 2020s.
Orbital debris is composed of defunct spacecraft, rocket bodies, and fragments from collisions or explosions. It poses a growing risk as the volume of debris increases. While SSA capabilities help operators avoid large debris, many small pieces remain untracked, representing the greatest risk to spacecraft.
Lastly, the growing presence of satellites and debris in orbit is affecting scientific measurements. Space telescopes are increasingly observing streaks caused by active satellites and debris, and space objects may also cause disturbances in the ionosphere. These disturbances may interfere with natural ionospheric data and require further research to determine how best to separate them from background noise.
Space situational awareness (SSA) involves the monitoring and understanding of space objects and their operating environments to ensure safe, stable, and sustainable activities in space. It encompasses the ability to detect, track, and characterize space objects, providing essential data to support operational decision-making and collision avoidance.
SSA is vital for sustainable space operations, providing the knowledge necessary to ensure safe, stable activities in space. The U.S. Government’s Space Surveillance System (SSN) tracks over 25,000 objects in space, but only objects larger than 10 cm in low Earth orbit (LEO) and 1 meter in geosynchronous orbit are reliably tracked. Smaller debris, however, remains largely untracked, posing significant risks to spacecraft. NASA estimates that there are around 100 million small debris pieces in space that are too small to track but large enough to damage spacecraft.
Space traffic coordination refers to the planning, coordination, and synchronization of on-orbit activities to enhance the safety and stability of space operations. This includes managing the increasing number of spacecraft and satellites to prevent collisions and reduce congestion in orbit.
Space traffic coordination (STC) involves the planning and synchronization of spacecraft activities to ensure safety and sustainability in space. The rapid increase in satellite deployments and the advent of new technologies, such as satellite constellations and autonomous spacecraft, have made coordination more important than ever. Dynamic space operations, including frequent maneuvers using electric propulsion and on-orbit refueling, may help mitigate collision risks but also introduce new challenges due to the unpredictability of space movements.
Orbital debris management is a vital aspect of space sustainability, addressing multiple facets. This includes minimizing the creation of new debris through better spacecraft design and operational practices, implementing procedures for spacecraft to avoid collisions with debris, and protecting missions from damage caused by debris strikes. Additionally, efforts are made to reduce risks associated with reentry of debris, characterize untracked debris populations, and explore debris remediation techniques, such as active removal or mitigation strategies.
Space weather awareness pertains to understanding and predicting natural space weather conditions, which are influenced by changing solar activity. Monitoring space weather is essential for safeguarding spacecraft and other space assets from solar radiation, geomagnetic storms, and other phenomena that can disrupt satellite operations, communications, and navigation systems.
Together, these areas of focus contribute to a comprehensive approach to maintaining a safe, sustainable, and resilient space environment, ensuring the continued viability of operations in Earth’s orbit.
Challenges to Sustainability in Earth’s Orbit
NASA has identified several key challenges that impede progress in space sustainability efforts.
The space community lacks a universally accepted framework for space sustainability, making it difficult to model and measure the interconnected risks of space operations, such as collisions with orbital debris or other spacecraft. While some models address specific aspects of space, there is no comprehensive approach that can evaluate the sustainability of risk management, investment decisions, and future missions.
NASA and the broader space community also lack a unified set of models that account for the complex interdependencies between risks from launch vehicles, spacecraft, debris, and the space environment. This gap makes it difficult to determine what constitutes sustainable space operations and assess actions to improve space sustainability. The evolving dynamics of spacecraft and debris further complicate this, as future conditions are highly uncertain.
Uncertainties in the space environment, such as the trajectories of debris and changes in plasma and radiation, contribute to risks in space operations. Reducing these uncertainties is key to improving sustainability, but it remains unclear which uncertainties need to be prioritized and how much reduction is necessary to drive meaningful progress.
Moreover, space sustainability is often at odds with mission interests. Missions may prioritize immediate success, sometimes at the expense of long-term sustainability, leading to negative consequences for other operators. The lack of alignment between short-term mission goals and long-term sustainability results in reduced attention to the latter.
Space sustainability requires a coordinated global response. While the U.S. Government is beginning to address the issue through policies and guidance, gaps remain, particularly in debris remediation and transparency regarding decisions that may compromise sustainability for mission benefits. NASA cannot solve this issue alone, and global cooperation is essential. However, legal, procedural, and cultural barriers hinder effective data sharing and collaboration among space operators.
NASA’s Strategy for Space Sustainability
To address these challenges, NASA has established a set of comprehensive goals aimed at enhancing sustainability in Earth’s orbit and beyond. These goals are designed to be mutually reinforcing, allowing for simultaneous pursuit while building on each other to drive long-term improvements in space sustainability.
Goal 1: Develop a Comprehensive Framework for Assessing Space Sustainability
NASA is committed to creating a robust framework that integrates essential metrics and models to assess the current state of space traffic and debris in Earth’s orbit. This framework will not only guide NASA’s decisions on sustainable practices but will also provide a clear set of metrics to evaluate space sustainability and inform the Agency’s investment priorities.
Objectives:
- Define comprehensive metrics and models to measure sustainability in space.
- Establish acceptable and desirable risk levels for space operations, ensuring they align with long-term sustainability goals.
- Annually report on NASA’s impact on space sustainability, including the Agency’s contributions to reducing space-related risks and improving operational practices.
Goal 2: Minimize Uncertainties in the Space Environment
Reducing uncertainties surrounding space operations and human spaceflight is a key priority for NASA. By enhancing space situational awareness and improving predictability, NASA aims to mitigate risks posed by debris and other space hazards.
Objectives:
- Investigate advanced methods for predicting the space environment, such as improved models for tracking orbital debris and forecasting space weather events.
- Explore innovative approaches to reduce debris creation, focusing on design, operational practices, and end-of-life disposal to prevent further pollution of space.
- Prioritize risk management strategies for existing debris, with an emphasis on debris removal, safe disposal, and collision avoidance technologies.
Goal 3: Develop and Transfer Technology to Support Space Sustainability
NASA will continue investing in advanced technologies that enhance space sustainability, particularly in the areas of orbital debris management, space traffic coordination, and debris-reduction technologies. These investments will help NASA and other U.S. space operators maintain sustainable and safe operations in space.
Objectives:
- Advance orbital debris management technologies, including systems for debris tracking, collision avoidance, and remediation techniques.
- Increase investments in space traffic management and environmental monitoring technologies to improve situational awareness and support sustainable space operations.
- Support the demonstration of debris-related technologies, promoting their adoption within the space industry and encouraging global collaboration.
Goal 4: Update Policies to Support Space Sustainability
To align its operational practices with space sustainability objectives, NASA will update its internal policies and standards. This includes revising guidelines for debris remediation and supporting research on sustainable space operations.
Objectives:
- Revise internal policies to incorporate space sustainability principles, ensuring that all missions align with best practices for debris mitigation and space traffic coordination.
- Develop policies related to debris remediation, including guidelines for the safe removal and disposal of debris from Earth’s orbit.
- Support international efforts on space debris management, fostering global cooperation on the issue of orbital debris and space sustainability.
Goal 5: Enhance Coordination and Collaboration
NASA will strengthen its partnerships with international space agencies, industry leaders, and academic institutions to create a unified global approach to space sustainability. By sharing data, best practices, and research, NASA will enhance coordination and collaboration within the space community.
Objectives:
- Engage with international space organizations to share best practices, collaborate on research, and improve global coordination on space sustainability initiatives.
- Strengthen partnerships with governmental and non-governmental space entities, fostering innovation and ensuring a unified response to space debris challenges.
- Foster the exchange of data and technical advancements, facilitating the global sharing of knowledge and technology to address space sustainability issues.
Goal 6: Improve NASA’s Internal Organization for Space Sustainability
NASA will establish a dedicated team focused on overseeing and coordinating the Agency’s space sustainability initiatives. This team will ensure that sustainability goals are integrated into all of NASA’s operations, and the Agency remains accountable for its commitments to a sustainable space environment.
Objectives:
- Create an empowered organizational entity responsible for leading NASA’s space sustainability efforts and ensuring alignment with strategic goals.
- Ensure consistent coordination of sustainability efforts across NASA, making certain that space sustainability is prioritized and embedded within all relevant areas of the Agency’s mission planning and operations.
Conclusion
NASA’s Space Sustainability Strategy represents a forward-thinking approach to managing the risks and challenges of an increasingly congested and dynamic space environment. By prioritizing research, technology development, policy updates, and global collaboration, NASA aims to lead efforts that ensure space remains accessible and safe for future generations. With rapid advancements in space technology and the growing importance of space to global economies, sustainable space operations will be crucial for continued space exploration and the preservation of the space environment.
