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A Doppler Asymmetric Spatial Heterodyne (DASH) interferometer is a device that is suited to making line-of-sight
measurements of thermospheric wind speeds from either ground- or space-based platforms. However, DASH
interferometer characteristics are sensitive to temperature changes. These instrument changes can be tracked
with calibration sources and subsequently corrected during data analysis. Even though these thermal effects
can be corrected, a quantitative understanding of the physics driving them is important for future instrument
designs. A previous study of the thermal behavior of a monolithic DASH system [Harlander et al, Opt. Express,
2010] measured a thermal response that was not consistent with a simplified model. It was suggested that this
discrepancy was a result of the rotation of various optical components caused by the thermoelastic distortion of
the monolithic interferometer elements which were cemented together yet had different coefficients of thermal
expansion. This distortion effect was not included in the simplified model. In this study we assemble an
interferometer with separate optical components which are allowed to expand independently with changes in
temperature and therefore eliminates any distortion due to stresses induced by different coefficients of thermal
expansion. Thus, by measuring the thermally induced change to the interference pattern generated by this
interferometer, we may characterize the thermal behavior of the system and verify whether all the relevant
physics is included in the simplified model. We find that the thermal drift measured by the experimental
interferometer closely matches that predicted by the model. This important result will help in the material
selection and overall design of future monolithic interferometers.
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