Poseidon-4 SAR Altimeter

Poseidon-4 is the primary nadir-pointing dual-frequency SAR radar altimeter for the Copernicus Sentinel-6 mission.^[1][2][3] It flies on Sentinel-6A Michael Freilich and Sentinel-6B, with WMO listing Sentinel-6A for 2021-2027 service and Sentinel-6B for 2026-2032 service.^[3] The main surface-height channel is Ku band at 13.575 GHz with 320 MHz bandwidth, paired with a 5.41 GHz C-band channel with 320 MHz bandwidth for dual-frequency ionospheric correction.^[1][3] Poseidon-4 uses interleaved operation to collect SAR high-resolution and pulse-limited low-resolution measurements, maintaining continuity with Jason-series altimetry while improving Sentinel-6 measurement detail.^[2][3] Its supported measurements include sea-surface height, significant wave height, wind speed, ice topography, and ionospheric correction support from the second frequency.^[1][3][2]