Micrometeoroids and Orbital Debris

• 26 Dec 2025

Source: TH

Why in News?  

The Micrometeoroids and Orbital Debris (MMOD) threat has regained attention after space debris damaged China’s Shenzhou-20 capsule. With expanding human spaceflight including Gaganyaan, protecting astronauts from high-velocity debris is now critical.

What are Micrometeoroids and Orbital Debris (MMOD)? 

• About: Micrometeoroids are naturally occurring tiny particles, ranging from a few micrometres to about 2 mm, mostly originating from asteroid collisions and comets. 
  • They travel at very high velocities (11–72 km/s), making even dust-sized particles carry enough kinetic energy at orbital speeds to cause critical or catastrophic damage to onboard systems. 
  • Whereas, orbital debris, also known as space junk, consists of human-made objects in Earth’s orbit that no longer serve any purpose, such as defunct satellites, rocket fragments, collision debris, and remnants of anti-satellite tests. 
    • They typically move at around 10 km/s, capable of causing severe damage on impact. 
    • Rising debris density raises the risk of a runaway collision cascade known as the Kessler Syndrome, which could make some orbits unusable. 
• Distribution: Orbital debris is mainly concentrated in Low Earth Orbit (LEO) between 200 km and 2,000 km altitude. There are around 34,000 trackable debris objects larger than 10 cm and over 128 million pieces larger than 1 mm in LEO. 
  • Micrometeoroids are present throughout space but are slightly more concentrated near Earth due to gravitational pull. They cause billions of micro-impacts annually on spacecraft operating in Earth’s orbit. 
• Global Mechanisms to Manage Space Debris:  
  • Outer Space Treaty 1967 (India is a Signatory): Article VI of the treaty makes states responsible for all national space activities, including private ones, but lacks enforcement mechanisms.  
  • Convention on International Liability for Damage Caused by Space Objects 1972  (India is a Signatory) : It imposes absolute liability for space object damage on Earth, requiring no proof of negligence, but enforcement is weak.  
  • Voluntary UN Guidelines on Deorbiting: The UN recommends deorbiting satellites within 25 years, but compliance rate is only around 30%. 
  • Inter-Agency Space Debris Coordination Committee (IADC): Brings together agencies such as NASA, European Space Agency, and ISRO to develop technical standards. 
    • These standards inform debris mitigation guidelines adopted by United Nations Committee on the Peaceful Uses of Outer Space (UNCOPUOS). 
    • The guidelines are non-binding, relying on voluntary compliance rather than enforcement. 
• India’s Measures for Space Debris Mitigation: India has launched the Debris Free Space Missions (DFSM) initiative, aiming to achieve zero-debris space missions by 2030 for all Indian space actors, public and private. 
  • IS4OM (ISRO System for Safe and Sustainable Space Operations Management) has been set up to integrate all efforts related to spaceflight safety, Space Situational Assessment (SSA), and debris mitigation in an increasingly congested orbital environment. 
  • The Network for Space Object Tracking and Analysis (NETRA) strengthens space surveillance and tracking capabilities. 
  • The Indian Space Policy 2023 explicitly emphasises space debris mitigation and SSA capacity building.

Protection of Gaganyaan Crew from MMOD 

• The Gaganyaan mission is a standalone human spaceflight without the option of docking with a space station in case of emergencies, making onboard safety critical.  
  • Since the mission duration is less than a week, the risk from large, catalogued space debris is very low, but protection is still required against small, high-velocity micrometeoroids and orbital debris.  
• Accordingly, ISRO has adopted internationally accepted MMOD protection standards, including passive shielding such as Whipple shields, designed to meet stringent human-rating requirements. These shields are validated using advanced simulation tools and hypervelocity impact tests at DRDO’s Terminal Ballistics Research Laboratory, where projectiles are fired at speeds of up to 5 km/s.  
  • Physical (Whipple) Shielding : Satellites use Whipple shields consisting of an outer bumper layer and an inner rear wall separated by a standoff distance. 
    • The bumper shatters incoming debris, spreading its energy over a wider area before it reaches the rear wall.  
    • Fragmentation and dispersion reduce impact energy, allowing the rear wall to absorb the load without failure. 

Frequently Asked Questions (FAQs) 

1.What are Micrometeoroids and Orbital Debris (MMOD)? 
Micrometeoroids are natural high-velocity space particles, while orbital debris consists of defunct human-made objects like satellites and rocket fragments in Earth’s orbit. 

2. Why is MMOD considered dangerous despite the small size of debris?
Due to extreme velocities (up to 72 km/s), even millimetre-sized particles can cause catastrophic damage to spacecraft systems.

3. What is the Kessler Syndrome?
It refers to a collision cascade where debris impacts generate more debris, potentially rendering certain orbits unusable.

4. What global mechanisms exist to manage space debris?
Frameworks include the Outer Space Treaty (1967), Liability Convention (1972), and technical guidelines by Inter-Agency Space Debris Coordination Committee, adopted by United Nations Committee on the Peaceful Uses of Outer Space, though they are largely non-binding.