Why does the supplemental file of my CEOS product include two ephemeris groups?

On the ground, the first ephemeris group computation is made using the state vector coming from the PCD (Payload Control Data) stream. This first ephemeris group is made on raw ephemeris data, and includes missing and corrupted values. Before it can be used for a set of geometrical corrections, the quality of this data must be improved.

Interpolations and corrections are therefore performed on the first ephemeris groups, and results are stored in the second ephemeris group. This second group is ALWAYS involved in the geometry model computation, and its quality influences absolute scene location accuracy. More.

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