Earth Monitoring Satellites Using SWIR Camera Technology

Low-Earth Orbiting (LEO) satellites use the visible, NIR and SWIR bands to monitor many aspects of the environment, including the health of farms, forests, streams, lakes, bays, and seas. Measuring air pollution, finding methane leaks, and monitoring other greenhouse gases has become important metrics for addressing the changing climate. Molecular vibrations create strong absorbance bands at key wavelengths in the NIR and SWIR wavelength range, creating spectral signatures detectable by imaging spectrometers or by multi- and hyper-spectral imagers (HSI).

For instance, imaging the earth’s surface in two or three spectral bands can be used to spot methane leaks due to the CH4’s strong absorbance at 1666 nm (1.666 µm). There is little overlap with water or CO2 absorption in that wavelength band. Contrasting that image with that of a band without strong absorbance reveals the presence of methane.

With the advent of low-cost nanosatellites, putting them up for mission lives of only 3 to 5 years reduces the requirements for radiation-hardened components, making it viable for LEO satellites to use terrestrial imagers. Discuss your earth monitoring application with Princeton Infrared Technologies, Inc. (PIRT) engineers to understand how to employ the 2-D SWIR array PIRT1280A1-12 in your design, including the possibilities of creating a larger field of view mosaic detector of several arrays.

Both of the PIRT imagers deliver high-sensitivity and high-resolution with high-definition formats while also providing high intra-scenic dynamic range with great linearity. Each array provides a wide range of programmable gain or full-well capacities, making them suitable whether in use for finding the weakest light intensities or for detection small variations in low absorbance at high sunlight levels. The wide wavelength sensitivity range of these sensors gives satellite designers the ability to use the same detector for spectral bands anywhere in the range of 400 to 1680 nm (0.4 to 1.7µm). The natural direct-band gap of lattice-matched InGaAs SWIR detectors provide even progression of high-sensitivity QE response across those wavelengths, in contrast to the weak and un-even response exhibited by colloidal quantum dot (CQD) detectors that have been recently introduced to the market.

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