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Fourier transform spectrometer (FTS) has many advantages, especially for greenhouse gases and air pollution
detection in the atmosphere, because a single instrument can provide wide spectral coverage and high spectral
resolution with highly stabilized instrumental line function for all wavenumbers. Several channels are usually
required to derive the column amount or vertical profile of a target species. Near infrared (NIR) and shortwave
infrared (SWIR) spectral regions are very attractive for remote sensing applications. The GHG and CO of
precursors of air pollution have absorption lines in the SWIR region, and the sensitivity against change in the
amounts in the boundary layer is high enough to measure mole fractions near the Earth surface. One disadvantage
of conventional space-based FTS is the spatial density of effective observation.
To improve the effective numbers of observations, an imaging FTS coupled with a two-dimensional (2D)-camera
was considered. At first, a mercury cadmium telluride (MCT)-based imaging FTS was considered. However, an
MCT-based system requires a calibration source (black body and deep-space view) and a highly accurate and
super-low temperature control system for the MCT detector. As a result, size, weight, and power consumption are
increased and the cost of the instrument becomes too high. To reduce the size, weight, power consumption, and
cost, a commercial 2D indium gallium arsenide (InGaAs) camera can be used to detect SWIR light. To
demonstrate a small imaging SWIR-FTS (IS-FTS), an imaging FTS coupled with a commercial 2D InGaAs camera
was developed. In the demonstration, the CH4 gas cell was equipped with an IS-FTS for the absorber to make the
spectra in the SWIR region. The spectra of CH4 of the IS-FTS demonstration model were then compared with
those of traditional FTS. The spectral agreement between the traditional and IS-FTS instruments was very good.
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