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 tradeoff 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 subindicators 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 subindicator targets, requirements must be met for accurate assessment of the dataset subject. For example, different subindicators 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.