Spectral calibration of the MethaneAIR instrument
<p>MethaneAIR is the airborne simulator of MethaneSAT, an area-mapping satellite currently under development with the goal of locating and quantifying large anthropogenic CH<span class="inline-formula"><sub>4</sub></span> point sources as well as diffuse emiss...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2021-05-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/14/3737/2021/amt-14-3737-2021.pdf |
| Summary: | <p>MethaneAIR is the airborne simulator of MethaneSAT, an area-mapping satellite currently under development with the goal of locating and quantifying large anthropogenic CH<span class="inline-formula"><sub>4</sub></span> point sources as well as diffuse emissions at the spatial scale of an oil and gas basin. Built to closely replicate the forthcoming satellite, MethaneAIR consists of two imaging spectrometers. One detects CH<span class="inline-formula"><sub>4</sub></span> and CO<span class="inline-formula"><sub>2</sub></span> absorption around 1.65 and 1.61 <span class="inline-formula">µ</span>m, respectively, while the other constrains the optical path in the atmosphere by detecting O<span class="inline-formula"><sub>2</sub></span> absorption near 1.27 <span class="inline-formula">µ</span>m. The high spectral resolution and stringent retrieval accuracy requirements of greenhouse gas remote sensing in this spectral range necessitate a reliable spectral calibration. To this end, on-ground laboratory measurements were used to derive the spectral calibration of MethaneAIR, serving as a pathfinder for the future calibration of MethaneSAT. Stray light was characterized and corrected for through fast-Fourier-transform-based Van Cittert deconvolution. Wavelength registration was examined and found to be best described by a linear relationship for both bands with a precision of <span class="inline-formula">∼</span> 0.02 spectral pixel. The instrument spectral spread function (ISSF), measured with fine wavelength steps of 0.005 nm near a series of central wavelengths across each band, was oversampled to construct the instrument spectral response function (ISRF) at each central wavelength and spatial pixel. The ISRFs were smoothed with a Savitzky–Golay filter for use in a lookup table in the retrieval algorithm. The MethaneAIR spectral calibration was evaluated through application to radiance spectra from an instrument flight over the Colorado Front Range.</p> |
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| ISSN: | 1867-1381 1867-8548 |