Satellite instrument to measure stratospheric winds

Abstract

The Stratospheric Wind Interferometer for Transport Studies (SWIFT) is a satellite-born limb-viewing instrument which will be capable of globally measuring horizontal winds at altitudes of between 20 and 40 km with a precision of < 5 m/s, a vertical resolution of 2 km and a horizontal resolution on the order of a hundred km. SWIFT will map stratospheric dynamics. The data from the instrument will be important input for models which seek to predict the global distribution of stratospheric ozone. In addition, the SWIFT data will provide observational input to tropospheric weather models, which are currently being extended to the stratosphere. With global stratospheric wind data, these enhanced models have the potential to significantly improve weather forecasting in the troposphere. The instrument will observe a thermal emission line of an abundant atmospheric constituent near 8 micrometers using a field widened Michelson interferometer. A doppler shift of the emission line is detected as a phase shift at the output of the interferometer. A 2D array detector monitors the phase both perpendicular to and along the limb, thus mapping the velocity field. The fundamental feasibility of the instrument will be shown. The basic instrument requirements are described and the instrument parameters are derived from them. The instrument will utilize radiatively cooled optics and Stirling cycle coolers for the detector and filters. This instrument will be suitable for inclusion on a medium to large satellite with multiple instruments. The lack of cryogens is consistent with its intended use on the operational weather satellites of the future.