Orbital debris, also known as space junk, refers to the human-made objects in space that no longer serve any useful purpose, including nonfunctional spacecraft, abandoned rocket stages, fragments from disintegration, explosions and collisions, and other debris released during spacecraft deployment, operations and mission end. Orbital debris poses a serious threat to operational spacecraft and satellites, and could jeopardize access to space. NASA has been at the forefront of understanding and addressing this growing problem through its Orbital Debris Program Office.
The Growing Problem of Orbital Debris
Since the launch of Sputnik in 1957, thousands of rockets and satellites have been placed in orbit around Earth. As the population of orbital objects continues to increase, so does the risk of collisions and accidental breakups that generate orbital debris. Currently, there are over 27,000 pieces of debris larger than 10 cm orbiting the Earth that are tracked. However, there are estimated to be over 100 million pieces between 1 mm to 1 cm in size, and even millions of particles smaller than 1 mm.
Orbital debris travels at extremely high velocities of up to 17,500 mph in low Earth orbit, fast enough for even tiny untracked debris to damage operational spacecraft. The risks are clearly demonstrated by events such as the 2009 collision between a U.S. communications satellite and a defunct Russian satellite, which generated over 2000 pieces of trackable debris. Without proper debris mitigation and remediation measures, debris collisions could trigger a cascade of breakups that exponentially increase the debris population, known as the Kessler syndrome. This could make certain orbital regions like low Earth orbit unusable for decades.
NASA’s Orbital Debris Program Office
Recognizing orbital debris as a serious issue, NASA established the Orbital Debris Program Office (ODPO) in 1979 at the Johnson Space Center in Houston, Texas. The ODPO has taken the lead nationally and internationally in understanding the orbital debris environment, developing mitigation guidelines and policies, and promoting awareness.
The ODPO is charged with continuously monitoring and characterizing the orbital debris environment. This involves conducting ground-based and space-based measurements using radars, telescopes, returned surfaces from the Space Shuttle and satellites, and impact experiments. The ODPO compiles this data to identify new debris sources and validate its orbital debris models, which describe and predict the current and future debris population.
In addition, the ODPO assesses the risks posed to spacecraft by orbital debris and develops new materials and designs to improve protection. Hypervelocity impact testing is performed to understand impact risks at different velocities and angles. The ODPO also develops engineering models to help programs assess debris impact risks.
A major focus of the ODPO is developing debris mitigation guidelines and working with NASA programs and international organizations to implement them. NASA was the first space agency to issue a comprehensive set of orbital debris mitigation guidelines in the 1990s. These evidence-based guidelines limit debris generation and recommend end-of-life disposal procedures, and have been adopted by the U.S. government and international organizations.
The ODPO also supports the development of orbital debris policies and represents NASA in international policy negotiations. Recently, the ODPO provided technical expertise during the update of the U.S. Government Orbital Debris Mitigation Standard Practices in 2019.
The Importance of Orbital Debris Research and Mitigation
There are several reasons why NASA’s continued leadership in orbital debris research and mitigation is critical:
Ensuring space sustainability: Orbital debris threatens the sustainable use of space, from Earth observation and scientific missions to commercial satellites enabling modern technology. Monitoring debris helps assess risks to spacecraft, while mitigation preserves the space environment.
Protecting astronauts on the ISS: The International Space Station faces a constant threat from orbital debris and performs debris avoidance maneuvers on a regular basis. The ODPO’s models help assess risks to the ISS and develop shielding.
Enabling space commerce: Orbital debris could significantly impact emerging space industries such as satellite mega-constellations planned by SpaceX and others. Following debris mitigation guidelines enables safe and sustainable growth of commercial space.
National security: Orbital debris puts key strategic assets like communications, GPS and intelligence satellites at risk. Preserving the space domain is critical for national security.
International leadership: With more countries and companies launching to space, international coordination on orbital debris is essential. NASA plays a vital role in developing consensus through international bodies.
Technological innovation: Advancing technologies to track smaller debris, shield spacecraft, remove large debris, and repurpose materials drives innovation with benefits beyond space.
Scientific knowledge: Measurements and models developed by the ODPO expand our understanding of the space environment and the risks it poses. This knowledge informs policy and protects space missions.
Long-term sustainability: Orbital debris poses a long-term challenge that will persist without proper mitigation and remediation. NASA is committed to preserving orbital space for future generations.
Summary
In an increasingly congested space environment, the work performed by NASA’s Orbital Debris Program Office is crucial for characterizing and mitigating threats posed by orbital debris. Through a sustained commitment to debris monitoring, model development, risk assessments, shielding, mitigation guidelines and international policy, NASA continues to provide vital leadership in addressing space sustainability challenges. As the number of satellites in orbit grows exponentially, NASA’s orbital debris expertise helps ensure space remains accessible for scientific discovery, commerce, security and exploration for decades to come.
