What is debris mitigation?
Debris mitigation encompasses all technical and operational measures taken throughout a satellite's lifecycle to minimise its contribution to the orbital debris environment. It applies from design (material choices, structural integrity) through operations (collision avoidance manoeuvres) to end of life (controlled deorbit or transfer to a disposal orbit).
Key mitigation measures
Passivation: At end of life, all stored energy sources — residual propellant, pressurised tanks, batteries — must be vented or discharged to prevent on-orbit explosions that would fragment the satellite into thousands of pieces. Explosions are the single largest source of tracked debris: historical examples include the Ariane 1 upper stage that exploded in 1986 and the NOAA-16 battery explosion in 2015. Post-mission disposal (PMD): LEO satellites must deorbit within 5 years (FCC rule, 2022) or be placed in a graveyard orbit below the operational shell. GEO satellites must be boosted ~300 km above GEO into a graveyard orbit at end of life. Collision avoidance: Operators must perform manoeuvres when conjunction probability exceeds defined thresholds (typically 1-in-1,000 to 1-in-10,000).
Design for demise
Satellites at altitudes below 600 km will eventually re-enter naturally, but components that survive re-entry and reach the ground pose ground casualty risk. Design for demise (D4D) uses materials that vaporise completely during atmospheric re-entry — replacing stainless steel and titanium tanks with aluminium equivalents — to reduce the casualty risk below the regulatory threshold of 1 in 10,000 for any individual object.