There are three main steps in the Level-2 processing chain:
- Compute time-derived geophysical/environmental parameters.
- Perform re-tracking and compute physical parameters.
- Compute Level-2 altimeter/radiometer geophysical processing.
Computing time-derived geophysical parameters involves:
- re-computing altitude, orbital altitude rate, location and Doppler correction, accounting for updated orbit data
- computing ionospheric corrections
- computing non-equilibrium and equilibrium ocean tide heights, tidal loading, solid earth tide height, equilibrium long period ocean tide height and pole tide height (using pole locations)
- computing the height of the mean sea surface above the reference ellipsoid
- computing the mean dynamic topography, the height of the geoid and the ocean depth/land elevation.
Performing retracking and computing physical parameters (both SAR and LRM modes) involves:
- discriminating echoes (ocean/lead, sea-ice, ice sheet margin or ocean/coastal)
- performing retracking (ocean/lead, sea-ice, ice sheet margin or ocean/coastal)
- computing physical parameters
- merging snow depth (ocean/lead and sea-ice only)
- performing a short-arc, along track ocean interpolation (ocean/lead and sea-ice only)
- estimating freeboards (ocean/lead and sea-ice only)
- performing a latitude limit check (ocean/lead and sea-ice only)
- (For SAR mode) performing modified slope correction (ice sheet margin and ocean/coastal only).
Level-2 altimeter/radiometer geophysical processing involves:
- inputting and checking Level-1 MWR products
- computing and correcting physical parameters according to platform data
- interpolating MWR data and computing MWR geophysical parameters
- computing altimeter wind speed and rain/ice flags
- computing wind, tropospheric corrections and inverted barometer according to meteorological data
- computing HF fluctuations of the atmospheric effect on the surface (dynamic atmosphere correction)
- computing sea state bias
- computing dual frequency ionospheric corrections
- building and checking Level-2 SRAL/MWR products.