A multifrequency microwave radiometer of the future

A description is given of a passive microwave remote sensing system designed to meet the observational needs of Earth scientists in the 1990s. This system, called the high-resolution multifrequency microwave radiometer (HMMR), is to be part of a complement of instruments in polar orbit that will form the Earth Observing System (Eos). As presently envisioned, the HMMR will consist of three separate instruments. These are the advanced microwave sounding unit (AMSU) presently under development for NOAA (US National Oceanic Atmospheric Administration), the advanced mechanically scanned radiometer (AMSR), and the electronically scanned thinned array radiometer (ESTAR). The AMSU will provide atmospheric soundings of temperature and water vapor using channels in the oxygen resonance band (50-60 GHz) and water vapor resonance line at 183 GHz. The AMSR is to be a microwave imager including channels at approximately 6, 10, 18, 21, 37, and 90 GHz, each with dual (linear) polarization. The ESTAR is an imaging radiometer operating near 1.4 GHz designed to obtain global maps of surface soil moisture with spatial resolution on the order of 10 km