New Technologies for Spaceborne Measurements of the Upper Troposphere and Lower Stratosphere: The Compact Adaptable Microwave Limb Sounder (CAMLS) Project

The upper troposphere and lower stratosphere (UTLS, roughly 10-20km altitude) is a critical region of Earth's atmosphere as it is where radiatively active species such as water vapor (the strongest greenhouse gas) and ozone exhibit steep vertical gradients and large spatial and temporal variability, and where changes in their abundances strongly influence global climate. Among the outstanding questions in UTLS science, many demand a continuing global record of vertically resolved composition measurements, such as can only be made from a spaceborne vantage point. The required vertical resolution can only be achieved by instruments observing in either limb viewing or solar/lunar/stellar occultation geometries. This paper describes technologies being developed to enable next-generation microwave limb sounding instruments to extend and augment the unique record of UTLS observations from the Microwave Limb Sounder (MLS) instrument on NASA's Aura satellite (launched in 2004).

The "Compact Adaptable Microwave Limb Sounder" (CAMLS) project is developing key receiver and spectrometer technologies that can form the core of both a "continuity MLS" instrument and a more advance 2D-scanning MLS sensor that can provide unprecedented spatial and temporal resolution UTLS measurements. The CAMLS-class of instruments can measure vertical profiles of a wide range of key atmospheric species including ozone, water vapor, tracers of atmospheric motion, tracers of pollution from various sources, and species associated with polar ozone destruction. All the CAMLS measurements are made in the 320-360 GHz spectral region using a single receiver based on low noise amplifier technology, followed by multiple 10 GHz-wide digital spectrometers that include a sideband separation facility.

Following CAMLS system integration and test, we plan to incorporate the CAMLS system into the previously developed Airborne Scanning Microwave Limb Sounder (A-SMLS) and perform test flights on NASA's high altitude ER-2 aircraft.