Evaluating Satellite Constellation Designs for Earth Observation Data Utility in Support of the UN SDGs

This work examines the ability of satellite constellation designs to provide the data needed to assess various indicators of the 17 United Nations (UN) Sustainable Development Goals (SDGs). With the rapid growth of satellites in orbit, there are now over 6000 satellites located between 500 km and 600 km altitude. This raises concerns regarding orbital congestion and collision risk. While new satellite constellations must account for these challenges, their societal benefits, such as through Earth observation (EO) data, global navigation satellite systems (GNSS) and communication services are undeniable. Furthermore, although metrics exist to rate the impact of satellites on the environment, the benefits of their data, particularly in advancing sustainability, must also be quantified to enable a more balanced trade-off between the advantages and drawbacks. EO data plays a crucial role in the progress toward improved social, economic, and environmental sustainability. Specifically, EO data can assist with many of the UN SDGs, with sub-indicators of goals 2-Zero Hunger, 6-Clean Water and Sanitation, 11-Sustainable Cities and Communities, and 15-Life on Land, being the main beneficiaries of this space data. For EO data to be used to assist with specific sub-indicator targets, requirements must be met for accurate assessment of the dataset subject. For example, different sub-indicators require varying spatiotemporal resolution, swath width and total observation duration. Each of these data factors are determined by system design aspects such as orbital regime placement, number of satellites in the constellation, and mission lifetime. Previous studies have considered constellation design in conjunction with a Science and Applications Traceability Matrix (SATM) to score the scientific utility of a mission using the ability of a system to meet chosen data requirements. This work introduces an evaluation function to assess system performance in relation to the data needs of UN SDG indicators, thus creating a "sustainability utility" score of the constellation design. The data requirements for several indicators are compiled and then used for the scoring criteria for constellation designs. Using a systems modelling approach, the utility of satellite systems of different size and orbit placement is compared. The results demonstrate the application of the score in an analysis aimed at minimising launch costs and maximising utility. For SDG 15, a clear optimised design providing 5 m spatial resolution and a 1-day temporal resolution, consisting of 2 satellites at 450 km altitude is identified. Additionally, applying the SATM to Sentinel-2 yields scores of 0.8571 for SDG 6, 0.5 for SDG 11, and 0.9062 for SDG 15, highlighting that while Copernicus program data provides valuable insights, its resolution is limited and could be enhanced through integration with higher-resolution commercial satellite data. Ultimately, this sustainability utility score could provide a standardised metric to evaluate future EO missions based on their data utility, facilitating a more informed trade-off between mission benefits and potential environmental impacts.