A static birefringent interferometer for the measurement of upper atmospheric winds

An instrument concept called the Birefringent Imaging Doppler Wind Interferometer (BIDWIN) is being validated in the Atmospheric and Space Physics Lab at the University of New Brunswick in collaboration with COM DEV Ltd (Ottawa, Canada) to determine its capabilities for measuring Doppler wind fields in the Earth’s nightglow. The instrument is adapted from a similar approach used to obtain two dimensional images of high speed (~1000 m/s) flow fields in plasmas at the Australian National University. For that application the precision of the wind measurements was not explored in detail. With BIDWIN, the intent is to obtain ~ 5 m/s precision on each bin of a CCD image of the wind field. An examination of the instrument concept and sensitivity of the wind measurements made using this approach is undertaken to determine the feasibility of this criterion. The BIDWIN has the advantage over other instruments that can be used for a similar purpose (such as the field widened Michelson interferometer and Fabry-Perot interferometer) in that it has no moving parts, has a large throughput, is light weight and is relatively cheap to construct. In this paper, the instrument concept is presented and the ideal and non-ideal instrument effects are explored. Calibration measurements conducted using a proto-type of the instrument are used to verify the instrument concept and confirm the feasibility of the approach for making atmospheric wind measurements.