The SLSTR operational processor is divided in to three major processing levels.
- Level-0 processing aims to extract and check the raw data contained in the instruments source packets. These data are time sorted and annotated. The Level-0 products are internal products, not disseminated to Sentinel-3 users.
- Level-1 processing uses Level-0 products to compute radiometric measurements for each SLSTR channel in both views. This includes radiometric calibration for thermal and solar channels, several tests concerning surface and cloud flagging, and the determination of pixels' properties such as day/night, position in the instrument grid or geographical position.
- Level-2 processing uses Level-1 products (measurements and annotations data files) to computed sea surface temperature, land surface temperature and fire radiative power. Annotations associated with each pixel/channel/view are verified and gathered in the Level-2 products.