Space, like any other ecosystem, has only a finite capacity to sustain orbital operations. The continuous growth of Space activities, the increasing reliance on services from Space, and the lower cost of deploying smaller and distributed missions in orbit, are all aspects that, on one side, can improve the quality of life for people on Earth, and, on the other side, can contribute to overloading the delicate Space ecosystem.

Based on previous research by the European Space Agency and within the space community on the definition of space debris indicator and space capacity [1-2], the THEMIS was conceived as the European Space Agency operational software for “Tracking the Health of the Environment and Missions in Space” [3-5]. The THEMIS software was designed to assess the impact of a space mission on the Space debris environment, and to determine the share of the capacity of Space used by the mission under analysis. It also allows the computation of the overall share of the Space capacity used by orbiting spacecraft and the analysis of definitions of orbital capacity and its thresholds. THEMIS was designed to raise awareness and encourage the whole Space community to pursue sustainable practices and future evolution of the Space environment around the Earth, while providing operators with a quantitative risk approach that takes into considerations the most relevant mission features.

The development of the THEMIS tool was led by Politecnico di Milano in collaboration with DEIMOS UK under a contract of the European Space Agency (ESA). This project has received funding from the European Space Agency within the ESA's Space Safety Programme and is planned for release in September 2024.

The project, kicked off in 2021, reached the formal final acceptance of the software in early 2024 and will be publicly presented on 25 June 2024 concurrently to the ESA Zero Debris Week though a Final Presentation of the THEMIS project and a 4-hour workshop where the THEMIS software will be presented to spacecraft operator and Space policy regulators, including a hands-on tutorial.

The THEMIS tool will be available to the whole Space community (i.e., satellite operators, regulators, Space debris experts, and general public) through its web user interface, which serves as the main interface for external users to access the information on the missions’ characteristics and assess their impact on the Space environment. In addition, it allows the user to have an overview of the overall status of the Space environment, and to registered users to submit their missions for evaluation of their environmental impact on the space debris environment.


[1] F. Letizia, S. Lemmens, Evaluation of the debris environment impact of the ESA fleet, 8th European Conference on Space Debris, 2021,

[2] F. Letizia, B. Bastida Virgili, S. Lemmens, Assessment of environmental capacity thresholds through long-term simulations, Advances in Space Research, Vol. 7, No. 7, 2023. doi: 10.1016/j.asr.2022.06.010

[3] Colombo C., Trisolini M., Gonzalo J. L., Giudici L., Frey S., Kerr E., Sánchez-Ortiz N., Letizia F., Lemmens S., “Design of a software to assess the impact of a space mission on the space environment”, 8th European Conference on Space Debris, European Space Agency, 20-23 Apr. 2021, paper number: 289,

[4] Colombo C., Trisolini M., Muciaccia A., Giudici L., Gonzalo J. L., Frey S., Del Campo B., Letizia F., Lemmens F., “Evaluation of the Space capacity share used by a mission”, 73rd International Astronautical Congress (IAC), Paris, France, 18-22 Sep. 2022, paper number IAC-22-A6.4.1.

[5] Colombo C., Muciaccia M., Giudici L., Gonzalo J. L., Masat A., Trisolini M., del Campo B., Letizia F., Lemmens F., “Tracking the health of the space debris environment with THEMIS, EUCASS-CEAS Conference 2023, 9-13 Jul. 2023, Lausanne.

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