Thermal imaging drift monitoring of Doppler asymmetric spatial heterodyne spectroscopy for wind measurement based on segmented edge fitting

Abstract

Doppler asymmetric spatial heterodyne spectroscopy is recently developed for spaceborne measurement of middle and upper atmospheric wind field, which relies on the accurate inverse of interferogram phase to calculate the Doppler shift of airglow emission lines. The change of temperature leads to thermal deformation of the optical and mechanical components, causing thermal drift of the imaging plane relative to detector, changing the distribution of interferogram phase on pixels, and directly introducing phase errors to affect the wind speed inversion. In order to reduce the influence of imaging thermal drift on phase inversion, this paper uses the segmented fitting method to detect the sub-pixel edges of notch patterns and monitor imaging thermal drift accordingly. In the thermal stability test of a near-infrared Doppler asymmetric spatial heterodyne interferometer prototype, the thermal imaging drifts and ambient temperature showed a high consistency in the trend of high-frequency oscillation, and the correlation coefficient can reach 0.86 after removing the baseline. After phase correct using the thermal imaging shift, the high-frequency oscillation of interferogram phase shift is also greatly suppressed. In order to further verify the accuracy of the algorithm, the influence of the data signal-to-noise ratio and the data distribution characteristic parameter errors used in the fitting on the edge detection was simulated. The results show that the edge detection accuracy is mainly restricted by the data signal-to-noise ratio and the accuracy of the fringe frequency parameters. When the error of the fringe frequency parameter used for fitting is less than 0.5%, the error of other data distribution characteristic parameters is less than 5%, and the data signal-to-noise ratio is more than 35 times, the algorithm in this paper can achieve a detection accuracy higher than 0.05 pixels.

Research on thermal stability of monolithic near-infrared Doppler asymmetric spatial heterodyne interferometer

“…At present, phase inversion mainly uses an inversion method based on the Fourier transform 23 , 24 . The process of this method is as follows.…”

“…At present, phase inversion mainly uses an inversion method based on the Fourier transform. 23,24 The process of this method is as follows. The real fringe data of the interferogram are transformed to the frequency domain by a Fourier transform, and the characteristic peaks are extracted in the frequency domain to obtain the target spectrum.…”

Novel Compact Polarized Martian Wind Imaging Interferometer

“…It uses the perfect Fourier transform relationship between the interferogram and the incident light spectrum to invert the Doppler frequency shift of the incident light spectrum by calculating the complex interferogram phase [19]. The representative instrument is the Michelson Interferometer for Global Highresolution Thermospheric Imaging (MIGHTI) [20,21], which was launched in 2019 and is used to detect the horizontal wind velocity profiles and thermospheric temperatures in the altitude range of 90-300 km. Due to the large OPD, the DASH technique has a large phase error in spectral recovery.…”