The University of Wisconsin Space Science and Engineering Center Absolute Radiance Interferometer (ARI): Instrument Overview and Radiometric Performance

Spectrally resolved thermal radiances measured from orbit with extremely high absolute accuracy (< 0.1 K, k = 3, brightness temperature at scene temperature) constitute a critical observation for future climate benchmark missions. The FTS approach is well suited for the combined requirement of ultra-high accuracy and broad spectral coverage at high spectral resolution. FTS technology inherently provides broad spectral coverage with a small number of detectors, a very well defined instrument line shape (ILS) that can be easily monitored and measured, and the spectral resolution required for accurate line shape and position determination and to accurately calibrate the spectral scale using well-known atmospheric absorption lines. The challenge in the IR FTS sensor development for a climate benchmark measurement mission is to achieve this ultra-high accuracy with a design that can be flight qualified, has long design life, and is reasonably small, simple, and affordable. In this area, our approach is to make use of components with strong spaceflight heritage (direct analogs with high TRL) combined into a functional package for detailed performance testing. The required simplicity is achievable due to the large differences in the sampling and noise requirements for the benchmark climate measurement from those of the typical remote sensing infrared sounders for weather research or operations. An instrument overview and summary of the radiometric performance of the Absolute Radiance Interferometer (ARI) at the University of Wisconsin Space Science and Engineering Center (UW-SSEC) will be presented.