Details on End-to-End Performance Simulators can be found on ESA’s site.

The End-to-End Mission Performance Simulator (E2ES) is a tool which simulates the End-to-End processing chain of a mission, i.e. from the observed (Earth/Space) scene or phenomena to the retrieved parameters, uses instrument performance models and assesses and characterizes the mission performance up to L2.

In addition, E2ES are used to support activities such as consolidating requirements at data product Level 0 (L0), Level 1 (L1) or Level 2 (L2), estimating the impact of error sources in the mission performance at L1 and L2 and early preparing the user community for the mission exploitation.