The Greenhouse gases Monitoring Instrument on GaoFen-5 satellite-II (GMI-II) uses spatial heterodyne spectroscopy (SHS) for quantitative monitoring of atmospheric greenhouse gases (GHG). Unlike the traditional SHS, the interferometer component of the GMI-II was designed with zero optical path difference offset, effectively improving spectral resolution while maintaining the same detector specifications. The secondary imaging system with non-isometric scaling of spatial and spectral dimensions was designed to decrease the integration time of a frame image or improve the spectral signal-to-noise ratio (SNR) under the same integration time. This paper introduces the design, manufacture, adjustment methods, and test results of the main performance indexes of the GMI-II that indicate that the spectral resolution of the O₂ A-band detection channel is better than 0.6 cm⁻¹ and other channels are better than 0.27 cm⁻¹. Under the typical radiance of other carbon monitors’ on-orbit statistics, the spectral SNR of the GMI-II is more than 300. These test results demonstrate that the GMI-II can be well adapted to quantitative remote sensing monitoring of atmospheric GHG.

Interference data obtained by a spatial heterodyne spectrometer (SHS) is subject to various error factors and suffers from complex phase distortion. Traditional phase correction methods, such as the Amplitude, Merzt, and Forman methods, extract phase distortion in the spectral domain and correct it, which cannot effectively correct spatial phase distortion. Through theoretical derivation and numerical simulation, the spatial phase distortion is firstly determined and corrected in the interference domain. The frequency-dependent phase distortion is then extracted in the spectral domain and corrected. This novel phase distortion correction method named the phase decomposition method was applied to the in-orbit interference data of Greenhouse gases Monitoring Instrument-II (GMI-II). Compared with traditional phase correction methods, the root-mean-square error of the spectrum corrected using the phase decomposition method is reduced by 81.37%.

In this paper, a spatial static polarization modulation interference spectrum technique is proposed, which combines polarimetric spectral intensity modulation (PSIM) technology and spatial heterodyne spectroscopy (SHS), and can obtain the total Stokes parameters of the target light simultaneously. Moreover, there are no moving parts or electronically controlled modulation parts. In this paper, the mathematical model of the modulation process and demodulation process of spatial static polarization modulation interference spectroscopy is deduced, a computer simulation is carried out, the principle prototype is developed, and a verification experiment is carried out. Simulation and experimental results show that the combination of PSIM and SHS can achieve high-precision static synchronous measurement of high spectral resolution, high time resolution, and continuous band complete polarization information.

Spatial heterodyne one-dimensional imaging spectrometer (SHIS) can simultaneously acquire hyperspectral information from different fields of view (FOVs). However, the dynamic range of SHIS is limited by the detector's performance. We propose a high dynamic range spatial heterodyne one-dimensional imaging spectroscopy (HD-SHIS) based on a digital micromirror device (DMD), which can control the exposure time of each FOV signal by adjusting the flip time of micromirrors on an M-bit DMD, realizing the simultaneous detection of strong and weak signals in FOVs with a theoretical improvement of the dynamic range by dB. Meanwhile, HD-SHIS utilizes a DMD to realize the Hadamard modulation of interference data in the spectral dimension, which can be used with the linear array detector to complete the detection of the imaging spectrum. We have built an HD-SHIS principle prototype and carried out dynamic range experiments. The experimental results show that HD-SHIS can achieve 48 dB dynamic range improvement by utilizing an 8-bit display width DMD.