Copernicus Sentinel-3 marine altimetry Level-2

Copernicus Sentinel-3 marine altimetry Level-2 (product ID SR_2_WAT) provides along-track sea-surface height, significant wave height, and altimeter wind speed from the SRAL dual-frequency SAR altimeter (Ku-band 13.575 GHz and C-band 5.41 GHz) carried on Sentinel-3A and Sentinel-3B.^[1][2] Sentinel-3A first data date is 2016-03-13; Sentinel-3B launched in April 2018. Along-track resolution is approximately 300 m at 20 Hz and approximately 7 km at 1 Hz; the product has no cross-track scanning capability. Geophysical corrections supplied in the file include dry and wet tropospheric, ionospheric, and sea-state bias corrections. Retracking uses SAMOSA+ for open-ocean waveforms, OCOG for coastal and ice surfaces, and MLE4 for pseudo-LRM mode; the precise distinction between SAMOSA+ and SAMOSA2 in the current processing baseline is not confirmed.^[2][3] Timeliness tiers are NRT (within 3 h of acquisition), STC (within 48 h), and NTC (within 1 month). The repeat cycle is 27 days. Products are in NetCDF inside Sentinel-SAFE packages, distributed open access under the Copernicus data licence via the Copernicus Data Space Ecosystem, processed by the EUMETSAT Marine Centre.^[3]