Matilde Monteiro, University of Aveiro; Pedro Casau, University of Aveiro; Nuno Carvalho, University of Aveiro
Keywords: Orbital aerodynamics, atmospheric drag, ADBSat, GOCE satellite
Abstract:
Very low Earth orbits (VLEO), typically classified as orbits below approximately 450 km in altitude, are becoming increasingly attractive for both commercial and scientific endeavours.
For instance, regarding Earth observation payloads, a reduction in orbital altitude improves spatial resolution for optical imaging systems, allowing for more detailed and accurate data collection. Similarly, RADAR and LiDAR systems benefit from an improved signal-to-noise ratio, leading to higher-quality measurements. For real-time communication applications, the reduced distance to Earth minimizes latency. Additionally, satellites in these orbits require lower launch costs while benefiting from a better radiation environment, which helps to protect sensitive electronics. However, such unique benefits also come with significant challenges. The presence of highly reactive atomic oxygen can degrade material performance over time, highlighting the need for new advanced material solutions. Sustained operation in VLEO also demands the development of novel propulsive technologies, such as air breathing electric propulsion to counteract the effects of atmospheric drag. Lastly, a precise understanding of these aerodynamic forces, atmospheric density, and thermospheric winds is essential for effective aerodynamic control and high-precision maneuvering [1].
In fact, the correct modeling of the aerodynamic forces that act on a satellite is one of the main sources of uncertainty that affects the operations in this environment, making it a critical area for research. In VLEO, the free molecular flow (FMF) theory has been applied in the derivation of an aerodynamics model due to the rarefied atmospheric air flow and high spacecraft velocities relative to the atmosphere [2]. Throughout the years, it has evolved through a combination of analytical and computational approaches. Analytical models, for example, the combinations of geometric analysis methods with gas-surface interaction models such as Sentman’s [3] and Moe et al.’s modifications [4], provided mathematical frameworks for estimating drag and lift coefficients. Numerical methods, including the Panel Method, Ray-Tracing Panel Method (RTP), Test-Particle Monte Carlo (TPMC), and Direct Simulation Monte Carlo (DSMC), have further improved calculation accuracy by leveraging detailed gas-surface interaction theories and molecular-level simulation techniques [5].
Because of the necessity for having a fast and accurate tool to correctly model the aerodynamics of a satellite, the ADBSat software was developed. It implements the panel method with a shading algorithm, where it is possible to choose the proper gas-surface interaction (GSI) model for specific conditions. It computes drag, lift, and moment coefficients for various orientations of the satellite based on its computer-aided design (CAD) model [6]. However, the results of ADBSat are highly sensitive to environmental conditions. This dependency significantly increases computational complexity, making these simulations challenging when working with large datasets.
To overcome this limitation, we propose the integration of artificial intelligence methods into the aerodynamic modeling process, as follows:
Development of a CAD model of the satellite;
Definition of its operational range, and corresponding environmental conditions;
Utilization of ADBSat to compute the aerodynamic force coefficients over a predefined grid of environmental states within the operational range;
Incorporation of artificial intelligence methods for efficient regression of ADBSat’s aerodynamic predictions;
Integration into an orbital simulator.
For testing the proposed methodology, the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was selected as the case study, because it was a geodynamics and geodetics mission that operated in VLEO, at an altitude of 250-270 km [7]. By applying the developed framework to GOCE’s flight data, this research aims to demonstrate the feasibility of computationally efficient and accurate aerodynamic force predictions in VLEO. This is essential for predicting satellite trajectories, avoiding collisions and ensuring the sustainable use of the space environment. This also opens the possibility of optimizing satellite designs to improve aerodynamic performance.
[1]: Crisp, N. H., Roberts, P. C. E., Livadiotti, S., Oiko, V. T. A., Edmondson, S., Haigh, S. J., Huyton, C., Sinpetru, L. A., Smith, K. L., Worrall, S. D., Becedas, J., Domínguez, R. M., González, D., Hanessian, V., Mølgaard, A., Nielsen, J., Bisgaard, M., Chan, Y.-A., Fasoulas, S., … Schwalber, A. (2020). The benefits of very low earth orbit for earth observation missions. Progress in Aerospace Sciences, 117, 100619. https://doi.org/10.1016/j.paerosci.2020.100619
[2]: Gini, F. (2014). Goce precise non-gravitational force modeling for POD applications. In Proceedings. https://api.semanticscholar.org/CorpusID:111725747
[3]: Sentman, L. H. (1961). Free molecule flow theory and its application to the determination of aerodynamic forces. Retrieved from https://api.semanticscholar.org/CorpusID:92321666
[4]: Moe, K., & Moe, M. M. (2005). Gas–surface interactions and satellite drag coefficients. Planetary and Space Science, 53(8), 793-801. https://doi.org/10.1016/j.pss.2005.03.005
[5]: Graziano, B. P. (2007). Computational modelling of aerodynamic disturbances on spacecraft within a concurrent engineering framework (Doctoral dissertation). Cranfield University. http://hdl.handle.net/1826/2426
[6]: Sinpetru, L. A., Crisp, N. H., Mostaza-Prieto, D., Livadiotti, S., & Roberts, P. C. E. (2022). ADBSat: Methodology of a novel panel method tool for aerodynamic analysis of satellites. Computer Physics Communications, 275, 108326. https://doi.org/10.1016/j.cpc.2022.108326
[7]: EO Portal. (s.d.). GOCE – Gravity field and steady-state ocean circulation explorer. Retrieved from https://www.eoportal.org/satellite-missions/goce
Date of Conference: September 16-19, 2025
Track: Atmospherics/Space Weather