Development of internally-calibrated, MMIC-based millimeter-wave radiometers to enable correction of wet-tropospheric delay for coastal zone altimetry

Critical microwave component and receiver technologies are under development to reduce the risk, cost, volume, mass, and development time for a high-frequency microwave radiometer needed to enable wet-tropospheric correction in the coastal zone and over land as part of the accelerated Tier-2 NRC Decadal Survey-recommended Surface Water and Ocean Topography (SWOT) Mission. Current satellite ocean altimeters include a nadir-viewing, co-located 18-37 GHz multi-channel microwave radiometer to measure wet-tropospheric path delay. However, due to the area of the instantaneous fields of view on the surface at these frequencies, the accuracy of wet path retrievals begins to degrade at approximately 50 km from the coasts. Additional higher-frequency microwave channels added to the Jason-class radiometers on the recommended SWOT mission will improve retrievals in coastal regions since their surface footprints are about five times smaller than the lower frequency ones. Specifically, high-frequency window channels at 92, 130 and 166 GHz are optimum for wet path delay retrievals in coastal regions. New, high-sensitivity, wide-bandwidth mm-wave radiometers using both window and sounding channels show good potential for over-land wet-path delay retrievals.