Abstract
Abstract. A new compact static wind imaging interferometer, called the Birefringent Doppler Wind Imaging Interferometer (BIDWIN), has been developed for the purpose of observing upper atmospheric winds using suitably isolated airglow emissions. The instrument combines a field-widened birefringent delay plate placed between two crossed Wollaston prisms with an imaging system, waveplates and polarizers to produce four fixed 90∘ phase-stepped images of the interference fringes conjugate to the scene of interest. A four-point algorithm is used to extract line-of-sight Doppler wind measurements across the image of the scene. The arrangement provides a similar throughput to that of a field-widened Michelson interferometer; however, the interferometric component of BIDWIN is smaller, simpler to assemble and less complicated to operate. Consequently, the instrument provides a compact, lightweight and robust alternative that can be constructed and operated with lower cost. In this paper, the instrument concept is presented, and the design and optimization of a prototype version of the instrument are discussed. Characterization of the lab prototype is presented, and the performance of the instrument is examined by applying the instrument to measure a low-velocity two-dimensional Doppler wind field with a high precision (5 m s−1) in the lab.
Highlights
Upper atmospheric motions in the mesosphere and lower thermosphere (MLT) region are dominated by large scale tides, planetary waves, as well as large-scale and small-scale gravity waves
This paper presented the concept, design and performance testing of a compact static birefringent interferometer called Birefringent Doppler Wind Imaging Interferometer (BIDWIN)
The feasibility of measuring upper atmospheric winds with a precision of 5 m s−1 using BIDWIN was validated by performing singlepoint wind and two-dimensional wind field observation in the lab
Summary
Upper atmospheric motions in the mesosphere and lower thermosphere (MLT) region are dominated by large scale tides, planetary waves, as well as large-scale and small-scale gravity waves. Several other interferometric techniques have been developed over the past 50 years for the purpose of detecting upper atmospheric motions using airglow emissions These instruments have provided valuable insights regarding the dynamics occurring in the region. The core component of the BIDWIN instrument is the field-widened birefringent interferometer (Langille et al, 2013a, 2020) placed between two crossed Wollaston prisms This configuration produces four images of the scene conjugate to the interference fringes at the detector (see Fig. 3). We present the overall requirements, which guide the design of a general high-resolution two-beam interferometer capable of wind measurements with precisions
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