The increasing number of satellites and space debris in Low Earth Orbit (LEO) is becoming a critical global issue.
Without international cooperation, this vital region of space risks becoming unusable. Space debris threatens operational satellites, scientific missions, and even the safety of astronauts.
This article explores the sources, impacts, and potential solutions to address this growing challenge.
Space Debris: A Closer Look
What is Space Debris?
Space debris refers to human-made objects in orbit that no longer serve a functional purpose. There are two main types of debris:
- Natural Debris: Includes meteoroids and other small fragments from comets and asteroids.
- Artificial Debris: Comprises defunct satellites, spent rocket stages, and fragments from collisions or explosions.
Where Does Space Debris Accumulate?
Most space debris resides in LEO, which spans 500 km above Earth’s surface. This region houses active satellites and scientific instruments but is also the primary location for discarded space hardware and orbital debris.
Understanding Low Earth Orbit (LEO)
What is LEO?
Low Earth Orbit (LEO) refers to an orbit around Earth at altitudes ranging from 180 km to 2,000 km. This region is the most frequently used orbital zone for satellites, including the International Space Station (ISS).
Orbital Mechanics of LEO
To remain in LEO, satellites must travel at a speed of approximately 7.8 kilometers per second. At this speed, the centrifugal force generated by their motion balances Earth’s gravitational pull, allowing them to maintain a stable orbit.
Satellites in LEO complete an orbit around Earth in roughly 90 minutes. Unlike suborbital objects, which return to Earth, or objects exceeding escape velocity, LEO objects remain in orbit unless affected by external forces like atmospheric drag.
Importance of LEO
Satellite Applications:
- LEO is ideal for Earth observation satellites, which provide high-resolution images and data.
- Many communication satellites and scientific missions use LEO for better transmission speeds and lower latency.
- LEO satellites are critical for global positioning systems (GPS).
International Space Station (ISS):
The ISS orbits in LEO, facilitating human space exploration and scientific research. Its location allows for regular resupply missions and ease of crew transport.
Cost-Effectiveness:
LEO missions are cheaper and easier to launch compared to higher orbits, due to reduced energy requirements.
The Scale of the Problem
Rising Numbers of Space Debris
Over the past 60 years of space exploration, more than 6,050 launches have placed approximately 56,450 objects into orbit. Currently, around 28,160 of these objects remain in space, monitored by the U.S. Space Surveillance Network. This network tracks:
- Objects larger than 5-10 cm in Low Earth Orbit (LEO)
- Objects between 30 cm to 1 m in Geostationary Orbit (GEO)
However, only about 4,000 of these objects are operational satellites.
Total Mass of Space Debris
Space debris now exceeds a total mass of 9,300 tonnes. Of the cataloged objects:
- 24% are satellites, with less than one-third still operational
- 11% are spent upper rocket stages and mission-related items, such as launch adapters and lens covers
Fragmentation Events in Space
Causes of Fragmentation
Since 1961, over 560 fragmentation events have been recorded in orbit. Of these:
- Only seven resulted from collisions
- The majority were caused by explosions of spacecraft and rocket stages
Explosions in Space
Explosions occur when discarded rockets or satellites contain leftover fuel. Over time, exposure to harsh space conditions degrades these objects’ structure, leading to:
- Leaks or mixing of fuel components
- Self-ignition and explosions
These events generate thousands of fragments, some smaller than 1 cm, which significantly increase the amount of space debris.
As the amount of space debris grows, collisions are projected to become the primary source of new debris, further compounding the problem.
Do You Know?
Kessler Syndrome challenges the Big Sky Theory proposed by NASA in 1978, which argued that the vastness of space would prevent space debris from becoming a long-term problem.
Key Sources Of Space Debris
Anti-Satellite Tests
Intentional satellite interceptions have significantly increased space debris. For instance, China’s 2007 FengYun-1C test alone increased the trackable debris population by 25%.
Other Contributors
- Rocket Motor Firings: Over 2,460 solid rocket motor firings have released aluminum oxide particles and slag into space.
- Reactor Core Ejections: In the 1980s, Russian reconnaissance satellites ejected reactor cores, releasing coolant droplets into orbit.
- Historic Experiments: The Midas missions in the 1960s released thin copper wires during radio communication experiments.
- Surface Erosion: Spacecraft surfaces degrade under ultraviolet radiation, atomic oxygen, and micro-particle impacts, shedding paint flakes and other materials.
High Area-to-Mass Objects
Observations by ESA’s Teide Observatory have identified objects with high area-to-mass ratios. These may originate from thermal covering materials of disposed satellites in GEO.
Notable Events
First In-Orbit Collision
The first accidental in-orbit collision occurred on February 10, 2009, at 776 km above Siberia. An American satellite,
Iridium-33, collided with a defunct Russian military satellite, Kosmos-2251, at a speed of 11.7 km/s.
The collision destroyed both satellites, generating over 2,300 trackable fragments, some of which have since reentered Earth’s atmosphere.
Debris Distribution and Density
Satellites in LEO face constant exposure to aerodynamic forces from the thin upper atmosphere. These forces eventually decelerate objects, causing them to reenter the atmosphere.
However, at altitudes above 800 km, air drag is less effective, and objects can remain in orbit for decades.
Debris concentrations are highest at altitudes of 800-1,000 km and around 1,400 km. Spatial densities in GEO and near navigation satellite orbits are significantly lower.
Forecast And Risks
Debris Growth
Current launch rates of around 110 annually, coupled with 10-11 fragmentation events per year, are steadily increasing the number of debris objects. Doubling the debris population could quadruple the risk of catastrophic collisions.
Kessler Syndrome
If debris growth continues unchecked, collisions will outpace explosions as the primary source of new fragments. This cascade effect, known as the Kessler Syndrome, could render LEO unusable for future missions. Timely international mitigation efforts are crucial to prevent this scenario.
Kessler Syndrome challenges the Big Sky Theory proposed by NASA in 1978, which argued that the vastness of space would prevent space debris from becoming a long-term problem.
Challenges in Space Situational Awareness
The increasing amount of space debris makes it more difficult to track and predict the movement of objects in orbit.
This creates challenges for satellite operators and space agencies in maintaining a clear understanding of the space environment.
Do You Know?
In 2023, ISRO successfully deorbited Megha Tropiques-1, demonstrating active debris removal capabilities.
Efforts To Tackle Space Debris Challenges
India’s Steps Towards Addressing Space Debris
- ISRO’s System for Safe and Sustainable Operations Management (IS 4 OM): Launched in 2022, this system monitors space objects that could pose collision threats. It predicts how debris evolves and creates strategies to minimize risks.
- Collision Avoidance Efforts: In 2022, ISRO successfully performed 21 collision avoidance maneuvers to protect its operational satellites from potential crashes with other objects in space.
- Centre for Space Debris Research: This specialized center, set up by ISRO, focuses on tracking debris and developing measures to reduce its impact.
- Project NETRA: Project NETRA serves as an early-warning system designed to detect space debris and other hazards. Its primary goal is to safeguard Indian satellites from collisions.
Global Efforts To Combat Space Debris
- Inter-Agency Space Debris Coordination Committee (IADC): Formed in 1993, this international forum brings together spacefaring nations to coordinate efforts against the growing problem of space debris.
- United Nations Committee on the Peaceful Uses of Outer Space (COPUOS): This committee creates guidelines to ensure the sustainable use of outer space, including strategies for managing and reducing debris.
- European Space Agency’s Clean Space Initiative: This initiative encourages innovation in technologies that prevent debris generation and focuses on removing existing debris to promote sustainable space operations.
UN’s Five Treaties on Space Activities
- Outer Space Treaty (1967): Outlines principles for space exploration and usage.
- Rescue Agreement (1968): Addresses the rescue and return of astronauts and space objects.
- Liability Convention (1972): Establishes liability for damage caused by space objects.
- Registration Convention (1976): Requires countries to register their space objects.
- Moon Agreement (1979): Governs activities on the Moon and other celestial bodies.
Although India has signed all five treaties, it has not ratified the Moon Agreement.
Future Directions
- Strengthening Tracking Systems: Improving tracking technology and creating more accurate orbital models will help monitor space debris more effectively.
- Better Coordination and Traffic Management: As space becomes more crowded, global collaboration and systems like automated “rights of way” can help manage congestion and reduce collision risks.
- Limiting Debris Creation: Encouraging reusable rockets and enforcing global regulations can minimize new debris. For instance, India recently launched its first reusable hybrid rocket, RHUMI-1, developed by Space Zone India.
- Active Debris Removal: Innovative solutions such as harpoons, magnets, and lasers are being developed to clean up space debris:
- Harpoons: Devices that latch onto debris for retrieval.
- Magnets: Used to attract and move debris containing magnetic materials.
- Lasers: Directed beams provide small thrusts to change debris paths, enabling safer reentry or relocation.
In 2023, ISRO successfully deorbited Megha Tropiques-1, demonstrating active debris removal capabilities.
- Using Graveyard Orbits: Satellites nearing the end of their service life in geostationary orbit can be relocated to graveyard orbits beyond 36,000 km using their remaining fuel. This reduces space clutter.
- Adhering to International Standards: Strict compliance with global guidelines, such as those from the International Association for the Advancement of Space Safety (IADC), is essential to maintain safe and sustainable space operations.