Introduction 4

Different types of orbits 6

Congestion levels and predictions 8

Risks 10

  1. Collision risks – the Kessler syndrome 10

  2. Re-entry risks 11

  3. Risks to scientific research and astronomy 12

Sources of space debris 13

Main technical and operational measures 14

  1. Limitation of debris released during normal operations 14

  2. Prevention of on-orbit break-ups 15

  3. Prevention of on-orbit collisions 15

    a) Spacecraft design and mission planning 16

    b) Space Surveillance and Tracking (SST) 16

    c) Space Traffic Coordination 17

    d) Collision avoidance (CA) manoeuvres 18

  4. Post-mission disposal 19

  5. In-space operations and services (ISOS) 20

Economic and industrial impacts of policy measures 21

Conclusion 23