ESA rehearses two independent satellite missions for one launch.

ESA says two separate operations teams at its European Space Operations Centre are rehearsing the launch and early-orbit phases of FLEX and Sentinel-3C. The satellites are scheduled to share a launcher from Kourou on September 15, then operate in closely related orbits.

The exercises test how independently managed missions coordinate when they need the same resources or when a problem affects both spacecraft. Scenarios include unexpected orbit parameters and ground-system failures. FLEX will study photosynthesis, while Sentinel-3C will monitor oceans, land, ice and the atmosphere. The rehearsals are preparations, not confirmation that launch or commissioning has occurred.