THOR - Towards Higher Levels of Autonomy and Robustness
in Space Operations through Uncertainty Management and Quantification

Spacecraft orbiting around small bodies are strongly perturbed by non-Keplerian effects. This may have an unstabilizing effect that could lead initially safe orbits to escape or collision trajectories. One major disturbance is the small body inhomogeneous gravity field. Because Earth-based sensors have limited resolution, the gravity has to be sensed while in flight. Gravity determination is a key enabler for low altitude mission phases such as descent and landing. Funded by Europe's H2020 program, THOR project aims to develop autonomous GNC capabilities that comprise the determination of an accurate gravity field approximation and its use for robust flight operations around small bodies.

1. J.C. Sanchez, and H. Schaub. "Simultaneous navigation and mascon gravity estimation around small bodies." Acta Astronautica, vol. 213, pp. 725-740, 2023. doi:10.1016/j.actaastro.2023.09.023

S3TSR Data Analysis - Manoeuvre Detection for Near-Orbiting Objects

Detecting whether geocentric satellites have maneuvered or not serves to update space awareness catalogs. These databases are used to assess conjunctions with other space assets or debris, thus it is vital to keep them up to date. We developed maneuver detection algorithms based on Kalman filtering and reachability analysis. These are validated by using radar tracklets from the Spanish surveillance network and maneuver data of ESA satellites (e.g. Sentinel). Radar-based systems offer the distinctive ability to track, without interruptions, all the objects passing through its scanning area.

1. J.M. Montilla, J.C. Sanchez, R. Vazquez, J. Galan-Vioque, J. Rey Benayas, and J. Siminski. "Manoeuvre detection in low Earth orbit with radar data." Advances in Space Research, vol. 72(7), pp. 2689-2709, 2023. doi:10.1016/j.asr.2022.10.026

Design of Novel Guidance and Control Algorithms for Advanced
Rendezvous Applications: Halo Orbits and Asteroid Exploration

Model predictive control denotes an ample set of techniques that use optimization to account for system dynamics and constraints. Still, actuator mishaps or poor model knowledge require dedicated solutions. Robust or learning-based MPC forms can intelligently handle system uncertainty. We used a chance-constrained approach to treat thrusters uncertainty in order to ensure safe rendezvous. We also studied recursive learning of the gravity model for orbit station-keeping around an asteroid. These works were core to my PhD dissertation.

1. J.C. Sanchez, R. Vazquez, J.D. Biggs, and F. Bernelli-Zazzera. "Orbit-attitude predictive control in the vicinity of asteroids with in-situ gravity estimation." Journal of Guidance, Control, and Dynamics, vol. 45, no. 2, pp. 262-278, 2022. doi:10.2514/1.G005572
2. J.C. Sanchez, F. Gavilan, and R. Vazquez. "Chance-constrained model predictive control for near rectilinear halo orbit spacecraft rendezvous." Aerospace Science and Technology, vol. 100, no. 105827, 2020. doi:10.1016/j.ast.2020.105827