System Design and Technology Development for an Azimuth Scanning Microwave Limb Sounder

The NRC's Earth Science and Applications from Space decadal survey calls for a mission (GACM) to study global atmospheric composition, "with sufficient vertical resolution to detect the presence, transport, and chemical transformation of atmospheric layers from the surface to the lower stratosphere." Microwave limb sounding is particularly well suited for providing this information for the upper troposphere and above. The Microwave Limb Sounders on Aura and UARS have provided global measurements that have: quantified the evolution of the ozone layer; characterized the water vapor and cloud ice feedback mechanisms affecting climate change; documented the long range transport of pollution through tracers like CO; and improved the accuracy of global circulation models used for weather and climate forecasts. The Scanning Microwave Limb Sounder (SMLS) concept builds on the success of these instruments by adding an azimuth scan and increasing the antenna height to greatly improve horizontal and vertical resolution. The measurement swath is wide enough to provide, depending on orbit inclination, six or more daily measurements over midlatitudes. SMLS will incorporate a novel antenna design that enables rapid horizontal scanning, 4 Kelvin receiver front ends, advanced digital receiver back ends, and several lessons learned from previous missions. We will discuss the instrument design, technology development and readiness, and our approach to on-orbit calibration. We will also discuss plans and goals for a demonstration instrument that takes advantage of technologies developed through ESTO and other NASA and non-NASA programs.

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