Technology for spaceborne passive microwave Earth remote sensing

Three technology areas in passive microwave remote sensing are discussed: (1) radiometer calibration and wideband load optimization; (2) electronic polarization basis rotation for polarization sensitive scanning instruments; and (3) large space antennas for precision high spatial resolution radiometric imaging. It is noted that precise radiometric calibration, dual polarization sensitivity, and narrow beam multiband scanning antennas with high main lobe efficiencies are critical to the success of future Earth remote sensing systems. Narrow efficient main beams impose stringent structural requirements on space antennas, particularly for geosynchronous or low-frequency application. Meeting this will require either large filled aperture antennas with surface control or potentially, synthetic aperture or phased array radiometers. Technological advances are expected to improve the accuracy and spatial resolution, reduce the risk of failure, and increase the number of observable degrees of freedom of spaceborne passive microwave imaging radiometers