Potential additional mitigation measures to address the proliferation of small satellites and large constellations

At its 33rd meeting in Houston, in March 2015, the IADC noted the emerging plans for large constellations of satellites in Low Earth Orbit (LEO) and recognized the potential for such systems to have an important influence on the evolution of the space debris environment and consequent impact on the population of artificial satellites orbiting the Earth. For these reasons, the SG approved the Action Item 33.1 "Potential Additional Mitigation Measures to Address the Proliferation of Small Satellites and Large Constellations" and assigned it to WG4. The proliferation of small satellites and the proposed large constellations raise potential issues for the long-term sustainability of the near-Earth space environment. The current IADC Space Debris Mitigation Guidelines were based on modeling assumptions about future activities in space that did not include the possibility of large satellite constellations, or potential large increases in small satellite deployment. Therefore, current guidelines may not be adequate to address new environmental issues raised by such systems/missions. There was, then, a need to consider the impact of the proliferation of small satellites and large constellations, and identify additional measures, if needed, to preserve the long-term sustainability of the space environment. The reliability of the operational phase, including post mission disposal (avoiding leaving the spacecraft or launch vehicles in the LEO protected region), may be of particular importance for large constellations. For example, for a large constellation, a ten percent failure rate for limiting orbital lifetime will likely have a larger impact on the debris environment, as compared to smaller deployments. The tasks of the AI 33.1 were the following: - Identify the trend in the proliferation of small satellites and review plans for large constellations; - Determine the potential inadequacies of the existing IADC Space Debris Mitigation Guidelines for the proliferation of small satellites and those large constellations; - Consider the potential risks presented by such systems; - Propose possible additional measures to mitigate the identified risks for SG's consideration, including any guidelines concerning altitude of initial deployment and reliability of propulsion systems, or other special measures to address risks that would result if large numbers of objects do not meet reliability targets; - Propose potential scenarios for WG2 simulations. Moreover, an assessment of the changes requested to the supporting document by the Steering Group in WG4 AI32.1 & AI 33.2 are to be considered, as these can affect the conclusions.