Environment capacity as an early mission design driver

Abstract

In recent years, several metrics have been proposed to quantify the impact of a mission on the space debris environment. In our previous work, we introduced the environmental capacity as the number and typology of missions that are compatible with the stable evolution of the debris environment. This concept enables the evaluation of the effectiveness of mitigation guidelines by looking at the use of environmental capacity due to existing missions. The current work will investigate how the same concept can also be applied as a tool during the design of a mission, facilitating the comparison of different mission architectures depending on their overall contribution to the debris environment. First, the paper will present the latest updates to the debris index used as a metric of the environment capacity, including the inclusion of a penalisation for objects with low trackability and an improved model for the break-up probability. Then, several application cases will be discussed to demonstrate its use as design driver. First, the relevance of adopting operational best practices (i.e. collision avoidance and disposal manoeuvres) will be studied for different spacecraft classes as a way of quantifying better than required behaviour. Then, the environmental impact of a mission will be analysed considering the case when the mission is realised through a single large satellite or through a constellation of smaller satellites. Finally, different end-of-life scenarios will be assessed to demonstrate the use of the method to discriminate between various technologies on a case-by-case basis. The adoption of passive de-orbiting systems will be compared to conventional disposal through de-orbit burns or operations at lower altitudes to gain insight into how two different options, both compliant to existing guidelines, differ in terms of the resulting environmental impact. Finally, a scenario with active-debris-removal will be considered, showing how the quantification of the impact on the debris environment can support the selection of parameters such as the rendez-vous altitude, based on the expected success rate of the capture and final disposal phase.