Sentinel-1 is a flagship mission of the Copernicus Programme of the European Union, dedicated to Earth observation and managed by the European Space Agency. The mission, currently composed of three satellites, provides critical radar imaging data for environmental monitoring, climate studies, land and maritime surveillance, and disaster response, both across Europe and worldwide. In-orbit support for the Sentinel-1 spacecraft is provided by Thales Alenia Space Italia (TAS-I) through ESA's maintenance contract, coordinated by the European Space Research and Technology Centre (ESTEC)’s Post-Launch Support Office. Mission operations are conducted at the European Space Operations Centre (ESOC) and the European Space Research Institute (ESRIN), with support from ESTEC and industrial contractors.

Following the in-flight anomaly of Sentinel-1B, multiple recovery attempts were made; however, the mission was officially declared ended in August 2022. Since then, the Sentinel-1 mission has relied exclusively on the Sentinel-1A satellite, until the launches of Sentinel-1C and Sentinel-1D, successfully performed on December 2024 and November 2025, respectively.

The disposal operations for Sentinel-1B, carried out between April 2023 and September 2024, successfully reduced the satellite's mean altitude from 700 km to 590 km, in compliance with international guidelines requiring uncontrolled re-entry within 25 years. This intensive maneuver campaign, executed at ESOC with support from TAS-I, provided a unique opportunity to extensively test the in-flight performance of the onboard hydrazine-based propulsion system.

To support these operations, TAS-I developed and validated a dedicated algorithm to estimate maneuver performance, including the characterization of individual thruster behavior during simultaneous firings; specifically, four thrusters were operated concurrently in open loop during these maneuvers. This predictive scheme demonstrated high effectiveness within the Sentinel-1B campaign and has subsequently been adopted for the initial orbit acquisition phases of Sentinel-1C and Sentinel-1D, establishing a new standard for in-flight operations support within the Sentinel-1 project.

This work introduces the developed algorithm, supported by flight data. The method consists of two sequential steps: first, overall maneuver performance is assessed using onboard orbital telemetry; second, individual thruster contributions are extracted from attitude control system telemetry.

Telemetry collected before and after each maneuver is processed as orbital parameters, with maneuver Delta-Vs computed by minimizing their residuals, and the maneuver impact evaluated using the Gaussian planetary equations. This approach enables precise estimation of maneuver effects without a full orbit determination process, while preserving a comparable level of accuracy.

Individual thruster effects are decoupled in the second stage by modeling the satellite's attitude response to commanded thrust activations. The model incorporates known satellite inertia and thruster mounting matrices, and accounts for both expected thruster effects and reaction wheel desaturation cycles, managed by the avionics via onboard magnetorquers. Telemetry residuals, derived from accumulated angular momentum in the reaction wheels, are used to estimate the contribution of each thruster.

This novel scheme enables accurate monitoring and prediction of thrust performance, which is essential for safe and efficient operations. Furthermore, it provides valuable data for enhancing thrust modeling and supporting the design of future missions.