Applications of high spectral resolution FTIR observations demonstrated by the radiometrically accurate ground-based AERI and the Scanning HIS aircraft instruments Henry E. Revercomb, Robert O. Knuteson, Fred A. Best, David C. Tobin, William L. Smith*, Wayne F. Feltz, Ralph A. Petersen**, Paolo Antonelli, Erik R. Olson Daniel D. LaPorte, Scott D. Ellington, Mark W.Werner, Ralph G. Dedecker, Ray K. Garcia, Nick N. Ciganovich, H.Benjamin Howell, Ken Vinson, and Steven A. Ackerman University of Wisconsin-Madison, Space Science and Engineering Center 1225 West Dayton Street, Madison Wisconsin, 53706 * NASA Langley Reseach Center ** NOAA/NCEP ABSTRACT Development in the mid 80s of the High-resolution Interferometer Sounder (HIS) for the high altitude NASA ER2 aircraft demonstrated the capability for advanced atmospheric temperature and water vapor sounding and set the stage for new satellite instruments that are now becoming a reality [AIRS (2002), CrIS (2006), IASI (2006), GIFTS (2005/6)]. Follow-on developments at the University of Wisconsin-Madison that employ interferometry for a wide range of Earth observations include the ground-based Atmospheric Emitted Radiance Interferometer (AERI) and the Scanning HIS aircraft instrument (S-HIS). The AERI was developed for the US DOE Atmospheric Radiation Measurement (ARM) Program, primarily to provide highly accurate radiance spectra for improving radiative transfer models. The continuously operating AERI soon demonstrated valuable new capabilities for sensing the rapidly changing state of the boundary layer and properties of the surface and clouds. The S-HIS is a smaller version of the original HIS that uses cross-track scanning to enhance spatial coverage. S-HIS and its close cousin, the NPOESS Airborne Sounder Testbed (NAST) operated by NASA Langley, are being used for satellite instrument validation and for atmospheric research. The calibration and noise performance of these and future satellite instruments is key to optimizing their remote sensing products. Recently developed techniques for improving effective radiometric performance by removing noise in post-processing is a primary subject of this paper. Keywords: interferometer, spectroscopy, remote sensing, calibration, radiometric performance 1. INTRODUCTION The AERI and the S-HIS provide up-looking and down-looking observations with high spectral resolution (0.5 cm -1 ) and broad infrared spectral coverage (3- up to 25 μm). Both realize high standards of radiometric accuracy by following and expanding on the calibration approaches developed for the HIS aircraft instrument. 1, 2 This accuracy has made possible a wide range of applications and products, including spectroscopy for improved radiative transfer models, high vertical resolution remote sensing of temperature and trace gases, surface emissivity and temperature, cloud radiative properties, satellite data validation, and related higher level products including atmospheric stability and water fluxes from combination with wind observations. The AERI instruments are also robust and well suited to continuous observing. 3-5 Multiple AERI instruments have successfully demonstrated autonomous operation for several years without any regular operator intervention, and routinely provide fully calibrated data through an internet link to the ARM science team. This robustness makes AERI an attractive candidate for broad deployment to detect detailed changes in the conditions of the planetary boundary layer. 6-7 Multispectral and Hyperspectral Remote Sensing Instruments and Applications, Allen M. Larar, Qingxi Tong, Makoto Suzuki, Editors, Proceedings of SPIE Vol. 4897 (2003) © 2003 SPIE · 0277-786X/03/$15.00 11