Approach:

Introduction: Define what constitutes large space debris objects and why they pose potential threats to Earth's atmosphere and surface.

Body: Highlight the potential threats involved. Discuss the existing or proposed measures to monitor, track, mitigate, or remove large space debris objects.

Conclusion: Recommend some standards or international protocols to prevent catastrophic incidents resulting from large space debris objects re-entry

Answer:

Large space debris objects are defunct human-made objects in space that no longer serve a useful function. The re-entry scenarios of these objects depend on their size, shape, orbit, speed, and atmospheric conditions. Some of them burn up completely in the atmosphere, while others survive partially or fully and impact the Earth.

Some examples of past or current large space debris objects are:

• The Skylab space station disintegrated in 1979, and some of its parts fell in western Australia.
• A 25-tonne Chinese rocket fell into the Indian Ocean in May 2021.
• An unburnt part of an ISRO PSLV rocket was found on a beach in western Australia in July 2023.

When these objects enter the Earth's atmosphere, they can pose various threats to humans and the environment:

1. Collision with other operational satellites or spacecraft causes damage or loss of functionality.
   • In 2009, a defunct Russian satellite collided with an operational US satellite, creating thousands of new debris fragments.
2. Re-entry: debris objects can re-enter the Earth's atmosphere and burn up partially or completely. Depending on their size, shape, speed, and angle of entry, some of them may survive the re-entry and impact the ground or water.
   • In 1978, a Soviet satellite carrying a nuclear reactor re-entered the atmosphere and scattered radioactive debris over Canada.
3. Explosion: due to internal pressure, battery failure, fuel leakage, or collision, which can create more debris fragments and increase the risk of collision or re-entry.
   • In 2007, China intentionally destroyed one of its own satellites with a missile, creating a large cloud of debris that endangered other satellites.
4. Electromagnetic interference: debris objects can interfere with the electromagnetic signals used for communication, navigation, or observation and affect the performance or reliability of satellites, spacecraft, ground stations, or devices that rely on these signals.
   • In 2016, a piece of space debris disrupted the signal of a European weather satellite, causing a temporary loss of data.
5. Environmental impact: they can release toxic substances, metals, or radioactive materials that can contaminate the air, soil, or water.
   • In 1997, a Russian rocket stage re-entered the atmosphere and released 1.5 tonnes of unburned fuel over Australia.
6. Economic impact: causes economic losses due to damage or destruction of satellites, spacecraft, or infrastructure, and can also increase the cost of launching and operating new missions in space due to the need for more shielding, manoeuvring, or debris removal.
   • In 2013, a meteor exploded over Russia and caused over $30 million in damage to buildings and injuries to people.
7. Legal and political impact: they can trigger disputes or conflicts between countries or entities over the use of space or the management of space debris.
   • In 2009, the US government paid $400 million to a private company for damages caused by a piece of space debris from a Chinese missile test.

According to the United Nations, there are some measures that can be taken to tackle space debris:

1. Passivation: removing the sources of energy from a spacecraft or a rocket stage at the end of its operational life, such as venting residual fuel or discharging batteries, to prevent on-orbit explosions that could create more debris.
2. Post-mission disposal: moving a spacecraft or a rocket stage to a safe orbit or reentry trajectory after its operational life to reduce the risk of collision with other objects or with the Earth's surface. For low Earth orbit (LEO), the recommended disposal time is within 25 years, and for geostationary orbit (GEO), the recommended disposal altitude is about 300 km above the GEO ring.
3. Collision avoidance: performing manoeuvres to avoid potential collisions with other objects based on orbital data and conjunction analysis. This requires accurate tracking and monitoring of space debris, as well as coordination and communication among operators.
4. Space traffic management: establishing rules and standards for safe and responsible behaviour in space, such as orbital slots, launch windows, frequency allocation, debris mitigation guidelines, etc. This requires international cooperation and policy development among space actors.
5. Active debris removal: using dedicated missions or technologies to capture and remove large and hazardous debris objects from orbit, such as nets, harpoons, tethers, lasers, etc.

To prevent catastrophic incidents from space debris re-entry, international standards and protocols include IADC and UN guidelines for space debris mitigation, ISO 24113 for mitigation measures, and space traffic management initiatives. Spacecraft re-entry safety standards and orbital debris removal efforts are also crucial. International collaboration on debris tracking and warnings aids collision avoidance. Adherence to these measures promotes responsible space operations and reduces the risks associated with space debris, ensuring safer and more sustainable use of outer space.