A Compact Fabry-Perot Interferometer with a Solid Etalon for Measuring Upper Atmospheric Wind and Temperature

Abstract. A compact solid etalon Fabry-Perot interferometer (SEFPI) with an effective aperture diameter of 70 mm has been developed for ground-based measurements of upper atmospheric winds and temperatures at an altitude of approximately 250 km. Unlike conventional FPIs employing air-spaced etalons, the SEFPI uses a solid etalon, enabling a more compact, lightweight, and cost-effective instrument design, while requiring stringent thermal stabilization. Laboratory validation using an acousto-optic frequency shifter (AOFS) to generate controlled Doppler shifts demonstrated the SEFPI’s high measurement accuracy, with an average wind uncertainty of 0.42 m/s and a root mean square error (RMSE) of 0.61 m/s. Field comparison validation was conducted via coincident ground-based measurements with two interferometry techniques. The first employed a Dual-Channel Optical Interferometer (DCOI), while the second utilized a well-established FPI employing a 100 mm diameter air-spaced etalon. The SEFPI measurements exhibited strong agreement with both instruments, yielding Pearson correlation coefficients exceeding 0.84. Statistical analysis yielded an overall mean wind difference of 1.88 m/s relative to the co-located DCOI instrument and 5.58 m/s relative to the conventional FPI located 502 km away. Temperature comparisons between the two FPIs revealed a correlation coefficient of 0.86 and an average difference of 62.38 K.