The routine accuracy assessment of Sentinel-2 is carried out by comparing the generated orbital products by the Copernicus POD Service against external orbits provided by ESOC, generated from independent observation RINEX [ftp://igscb.jpl.nasa.gov/pub/station/general/antex14.txt] directly decoded from the GPS L0 files.
In the case of the predicted orbit, given its more relaxed requirements, its accuracy assessment is carried out against the RESORB product after verifying that this one is close to the external solution.
The following figures show that the accuracy requirements are regularly met. The cases in which they are not are usually related to manoeuvres or GPS data outages.
Figure 2: Orbit comparison of Sentinel-2 PRE orbital products (AUX_PREORB) against CPOD RESORB