Space Debris and Responsible Orbit Operations

The number of objects in low Earth orbit has risen rapidly over the last decade. While small satellite constellations democratise space, they also raise the risk of orbital debris. Responsible operators need to address this problem from the design stage.

Scale of the problem

Today more than 36,000 objects larger than 10 cm are regularly tracked, only a small fraction of which are active satellites. The number of fragments smaller than 1 cm runs into millions. At 7.6 km/s in orbit even a bolt can disable a satellite in a collision.

The five-year rule

The Inter-Agency Space Debris Coordination Committee (IADC) and national authorities recommend that low-orbit satellites re-enter the atmosphere within 25 years of mission end at most, and increasingly within five. All Gökbilge GU-series satellites are designed to this target.

Design measures

• End-of-life propulsion: Lowering altitude with electric propulsion
• Drag sail: A film deployed at mission end for passive altitude loss
• Passivation: Venting fuel and battery energy at mission end
• Collision avoidance: Manoeuvre planning with the ground-station network and tracking data

The launcher side

Launcher upper stages are also a source of debris. In the ÜF-250, the second stage is designed to be re-ignited at the end of the mission to steer it into the atmosphere and vent remaining propellant.

Regulatory framework

Alongside frequency allocation, international registration and launch permits, submitting a space-debris mitigation plan is becoming mandatory. Preparing this plan at project start lowers later compliance cost.

Recommendations for small satellite operators

• Choose the lowest practical orbit altitude (below 500–550 km natural decay is fast)
• Create and document an end-of-life plan for each satellite
• Agree conjunction warning services with tracking data providers
• Plan continuity of ground-station network access

Cost impact

An additional 3–6% of total satellite cost should be reserved for the end-of-life plan: propellant or drag sail, extra testing and operations time. Considering collision risk and potential insurance premium increases, however, this investment is cheap in the long term.

International cooperation

Operators sharing data with one another for conjunction warnings is the basis of space traffic management. Gökbilge is ready to share orbit data obtained from its ground-station network transparently with other operators and takes part in international data-sharing initiatives for this purpose.