Objective Due to the overlap and interference of the absorption peaks of CO₂ and CH₄ in the short-wave infrared, and the contradiction between sensitivity and dynamic range, the existing greenhouse gas grating spectrometers cannot realize the simultaneous observation of CO₂ and CH₄ with high precision. In order to accurately measure the content of greenhouse gases CO₂ and CH₄ in the atmosphere, a short-wave infrared imaging spectrometer with high resolution and high signal-to-noise ratio based on Indium Gallium Arsenide (InGaAs) infrared detector was designed and developed independently. At the same time, to enable the spectrometer to achieve excellent performance and meet the requirements of high-quality imaging and high-precision measurement, a performance optimization method for infrared spectrometers is proposed.

Methods First of all, based on the application scenarios of the equipment, it is proposed that the spectrometer band should cover 1595-1 675 nm, the resolution should be less than 0.3 nm, and the signal-to-noise ratio should not be less than 407. According to the requirements of the indicators, the relevant design of optics and electronics is completed, and the Littrow structure and InGaAs infrared detector are selected. Subsequently, in the imaging process of InGaAs infrared detector, there are blind pixels and inconsistent response problems caused by factors such as uneven material doping and manufacturing process deviation. A spectrometer optimization method including blind pixel detection, blind pixel compensation, non-uniformity correction and optimal temperature selection is proposed to make the spectrometer have the best working performance and improve its imaging quality and measurement accuracy.

Results and Discussions The infrared spectrometer sample gas measurement experiment is carried out. The experimental results show that the spectrometer has the highest signal-to-noise ratio near 0 °C, and the sample gas measurement results of the spectrometer are more accurate. The measurement error of 20000 ppm CO₂ sample gas is less than 2.5%, and the measurement error of 998 ppm CH₄ sample gas is less than 3.5%. The measurement error of the mixed sample gas of CO₂ and CH₄ is less than 5.5%, and the fitting residual error is 7.2×10⁻⁴. The measurement results of the sample gas are more accurate and meet the design requirements of the spectrometer.

Conclusion Through optimization, the measurement band range of the short-wave infrared spectrometer is 1595-1675 nm, the spectral resolution is better than 0.3 nm in the measurement band, and the signal-to-noise ratio is better than 440 in the actual measurement, which fully meets the requirements of the spectrometer. The spectrometer has high measurement accuracy and imaging quality, which can provide strong support for the subsequent accurate measurement of greenhouse gases CO₂ and CH₄, and also lay the foundation for the next airborne measurement.