Comparison of Stacked Sentinel-3 A&B and AltiKa Repeat Cycle Data

Sentinel-3 A&B radar altimeters yield sea surface height measurements in both a high-precision Synthetic Aperture Radar Mode (SARM), and a Pseudo-Low Resolution Mode (PLRM). We stacked repeat cycles from both missions and in both modes to compare their resolution of small seamounts. Stacking entailed removing non-geoidal heights and height errors, testing for consecutive measurements over ocean, aligning to common locations at 1 km intervals along a synthetic track, and forming a median height profile. These profiles are available from the National Centers for Environmental Information (NCEI) data repository. Global maps show that, over the oceans, the median height is usually derived from more than 49 cycles, and the typical error in an individual PLRM measurement is approximately 1.9 times greater than an individual SARM measurement. We applied a seamount detection bandpass filter to the median profiles and compared their spectral resolution to that of the Satellite for ARgos and AltiKa (SARAL) AltiKa mission. Small seamounts are similarly resolved by Sentinel-3 A&B SARM data and by the SARAL/AltiKa data.