Scientific Assessment of the SWIFT Instrument Design

Abstract

he Stratospheric Wind Interferometer for Transport Studies (SWIFT) is a proposed satellite instrument. SWIFT is an imaging field-widened Doppler Michelson interferometer. It observes a thermal IR atmospheric emission line in a limb-viewing geometry in order to measure stratospheric winds and stratospheric ozone concentration profiles with global coverage during both day and night. SWIFT has the capability of improving the knowledge of the dynamics of the stratosphere and global distribution of and global transport of ozone. The target wind and ozone accuracies are 3 m s?1 and 5%?10%, respectively. The instrument is a follow up to the highly successful Canada?France Wind-Imaging Interferometer (WINDII) instrument on NASA's Upper Atmosphere Research Satellite (UARS). To assess the suitability of the method of Doppler imaging Michelson interferometry for the measurement of stratospheric wind and ozone using the SWIFT instrument, a scientific assessment of the instrument performance was undertaken using forward and inverse modeling and error analyses. This paper is aimed at determining the technical and scientific feasibility of the SWIFT instrument and its ability to meet the science requirements. This paper also briefly describes the SWIFT experiment, the data retrieval algorithms, and technical challenges in stratospheric wind measurements. Meeting the wind accuracy requirement imposes tight requirements on instrument thermal stability, filter monitoring, and determination of reference phase calibration. The SWIFT instrument design shows a strong level of dependence on the knowledge of atmospheric N2O concentration. The presence of N2O as an interfering species degrades the SWIFT performance at all altitudes with the largest impact especially for altitudes below 30 km.