Near-infrared broadband cavity-enhanced sensor system for methane detection using a wavelet-denoising assisted Fourier-transform spectrometer

The Analyst ◽  
2018 ◽  
Vol 143 (19) ◽  
pp. 4699-4706 ◽  
Author(s):  
Kaiyuan Zheng ◽  
Chuantao Zheng ◽  
Zidi Liu ◽  
Qixin He ◽  
Qiaoling Du ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Spectral Range ◽  
Near Infrared ◽  
Wavelet Denoising ◽  
Visible Spectral Range ◽  
Sensor System ◽  
Trace Gas ◽  
Fourier Transform Spectrometer ◽  
Methane Detection

The majority of broadband cavity-enhanced systems are used to detect trace gas species in the visible spectral range.

Stratospheric Trace Gas Measurements in the Near-UV and Visible Spectral Range with the Sun as a Light Source Using a Fourier Transform Spectrometer

1996 ◽  
Vol 50 (5) ◽  
pp. 583-587 ◽  
Author(s):  
Justus Notholt ◽  
Klaus Pfeilsticker
Keyword(s):  
Fourier Transform ◽  
Spectral Range ◽  
Visible Spectral Range ◽  
The Arctic ◽  
Trace Gas ◽  
Fourier Transform Spectrometer ◽  
The Sun ◽  
Gas Measurements ◽  
Atmospheric Trace Gas ◽  
First Time

Spectra of the atmosphere have been measured in the near-UV and visible spectral range for the first time with a Fourier transform spectrometer using direct and zenith scattered sunlight. The observations were performed in the Arctic at 79°N, 12°E in 1994. Spectra were recorded in the wavelength range 310 to 1100 nm up to a resolution of about 0.0008 nm. The use of the FT spectrometer allowed the study of atmospheric trace gas concentrations in the whole spectral region between 500 and 31,000 cm−1 (0.3–20 μm) with one instrument by only changing the beamsplitters and choosing different detectors. At a spectral resolution of 1.2 nm, the atmospheric absorptions of O3 around 505 nm and NO2 at 448 nm were analyzed. Results are compared with observations performed in the infrared with the same instrument, with TOMS data and with ozone balloon data.

scholarly journals Satellite monitoring of different vegetation types by differential optical absorption spectroscopy (DOAS) in the red spectral range

2007 ◽  
Vol 7 (1) ◽  
pp. 69-79 ◽  
Author(s):  
T. Wagner ◽  
S. Beirle ◽  
T. Deutschmann ◽  
M. Grzegorski ◽  
U. Platt
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Spectral Range ◽  
Near Infrared ◽  
Vegetation Type ◽  
Differential Optical Absorption Spectroscopy ◽  
Trace Gas ◽  
Satellite Monitoring ◽  
Optical Absorption Spectroscopy ◽  
Vegetation Types

Abstract. A new method for the satellite remote sensing of different types of vegetation and ocean colour is presented. In contrast to existing algorithms relying on the strong change of the reflectivity in the red and near infrared spectral region, our method analyses weak narrow-band (few nm) reflectance structures (i.e. "fingerprint" structures) of vegetation in the red spectral range. It is based on differential optical absorption spectroscopy (DOAS), which is usually applied for the analysis of atmospheric trace gas absorptions. Since the spectra of atmospheric absorption and vegetation reflectance are simultaneously included in the analysis, the effects of atmospheric absorptions are automatically corrected (in contrast to other algorithms). The inclusion of the vegetation spectra also significantly improves the results of the trace gas retrieval. The global maps of the results illustrate the seasonal cycles of different vegetation types. In addition to the vegetation distribution on land, they also show patterns of biological activity in the oceans. Our results indicate that improved sets of vegetation spectra might lead to more accurate and more specific identification of vegetation type in the future.

scholarly journals Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

2015 ◽  
Vol 8 (6) ◽  
pp. 2473-2489 ◽  
Author(s):  
J. Ungermann ◽  
J. Blank ◽  
M. Dick ◽  
A. Ebersoldt ◽  
F. Friedl-Vallon ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Horizontal Resolution ◽  
Trace Gas ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Ionization Mass ◽  
Fourier Transform Spectrometer ◽  
Upper Troposphere ◽  
Mixing Ratios

Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 High Altitude LOng Range (HALO) research aircraft during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H2O, O3, HNO3) volume mixing ratios from GLORIA dynamics mode spectra that are spectrally sampled every 0.625 cm−1. A total of 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line of sight. Simultaneous in situ observations by the Basic Halo Measurement and Sensor System (BAHAMAS), the Fast In-situ Stratospheric Hygrometer (FISH), an ozone detector named Fairo, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in situ trace gas data, and discrepancies can to a large extent be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments. This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.

scholarly journals Retrieval of atmospheric CH<sub>4</sub> vertical information from ground-based FTS near-infrared spectra

2019 ◽  
Vol 12 (11) ◽  
pp. 6125-6141 ◽  
Author(s):  
Minqiang Zhou ◽  
Bavo Langerock ◽  
Mahesh Kumar Sha ◽  
Nicolas Kumps ◽  
Christian Hermans ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Mole Fraction ◽  
Atmospheric Chemistry ◽  
Near Infrared ◽  
Satellite Observations ◽  
Total Carbon ◽  
Fourier Transform Spectrometer ◽  
Aircraft Measurements ◽  
Retrieval Software ◽  
Total Column

Abstract. The Total Carbon Column Observing Network (TCCON) column-averaged dry air mole fraction of CH4 (XCH4) measurements have been widely used to validate satellite observations and to estimate model simulations. The GGG2014 code is the standard TCCON retrieval software used in performing a profile scaling retrieval. In order to obtain several vertical pieces of information in addition to the total column, in this study, the SFIT4 retrieval code is applied to retrieve the CH4 mole fraction vertical profile from the Fourier transform spectrometer (FTS) spectrum at six sites (Ny-Ålesund, Sodankylä, Bialystok, Bremen, Orléans and St Denis) during the time period of 2016–2017. The retrieval strategy of the CH4 profile retrieval from ground-based FTS near-infrared (NIR) spectra using the SFIT4 code (SFIT4NIR) is investigated. The degree of freedom for signal (DOFS) of the SFIT4NIR retrieval is about 2.4, with two distinct pieces of information in the troposphere and in the stratosphere. The averaging kernel and error budget of the SFIT4NIR retrieval are presented. The data accuracy and precision of the SFIT4NIR retrievals, including the total column and two partial columns (in the troposphere and stratosphere), are estimated by TCCON standard retrievals, ground-based in situ measurements, Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) satellite observations, TCCON proxy data and AirCore and aircraft measurements. By comparison against TCCON standard retrievals, it is found that the retrieval uncertainty of SFIT4NIR XCH4 is similar to that of TCCON standard retrievals with systematic uncertainty within 0.35 % and random uncertainty of about 0.5 %. The tropospheric and stratospheric XCH4 from SFIT4NIR retrievals are assessed by comparison with AirCore and aircraft measurements, and there is a 1.0 ± 0.3 % overestimation in the SFIT4NIR tropospheric XCH4 and a 4.0 ± 2.0 % underestimation in the SFIT4NIR stratospheric XCH4, which are within the systematic uncertainties of SFIT4NIR-retrieved partial columns in the troposphere and stratosphere respectively.

scholarly journals Crystallization and visible–near-infrared luminescence of Bi-doped gehlenite glass

2018 ◽  
Vol 5 (12) ◽  
pp. 181667 ◽  
Author(s):  
M. Majerová ◽  
R. Klement ◽  
A. Prnová ◽  
J. Kraxner ◽  
E. Bruneel ◽  
...  
Keyword(s):  
Spectral Range ◽  
Near Infrared ◽  
Broad Band ◽  
Visible Spectral Range ◽  
Peak Temperature ◽  
Minor Amount ◽  
Glass Microspheres ◽  
Scanning Calorimetry ◽  
Crystallization Peak ◽  
High Temperature Xrd

Gehlenite glass microspheres, doped with a different concentration of Bi 3+ ions (0.5, 1, 3 mol%), were prepared by a combination of solid-state reaction followed by flame synthesis. The prepared glass microspheres were characterized from the point of view of surface morphology, phase composition, thermal and photoluminescence (PL) properties by optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and PL spectroscopy. The closer inspection of glass microsphere surface by SEM confirmed a smooth surface. This was further verified by XRD. The basic thermal characteristics of prepared glasses, i.e. T g (glass transition temperature), T x (onset of crystallization peak temperature), T f (temperature of the inflection point of the crystallization peak) and T p (maximum of crystallization peak temperature), were estimated from the DSC records. High-temperature XRD experiments in the temperature interval range 600–1100°C were also performed. The PL emission properties of prepared glasses and their polycrystalline analogues (glass crystallized at 1000°C for 10 h) were studied in the visible and near-infrared (NIR) spectral range. When excited at 300 nm, the glasses, as well as their polycrystalline analogues, exhibit broad emission in the visible spectral range from 350 to 650 nm centred at about 410–450 nm, corresponding to Bi 3+ luminescence centres. The emission intensity of polycrystalline samples was found to be at least 30 times higher than the emission of their glass analogues. In addition, a weak emission band was observed around 775 nm under 300 nm excitation. This band was attributed to the presence of a minor amount of Bi 2+ species in prepared samples. In the NIR spectral range, the broad band emission was observed in the spectral range of 1200–1600 nm with the maxima at 1350 nm. The chemistry of Bi and its oxidation state equilibrium in glasses and polycrystalline matrices is discussed in detail.

scholarly journals Athermal planar-waveguide Fourier-transform spectrometer for methane detection

2017 ◽  
Vol 25 (26) ◽  
pp. 33018 ◽  
Author(s):  
Hugh Podmore ◽  
Alan Scott ◽  
Pavel Cheben ◽  
Chris Sioris ◽  
Peter Cameron ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Planar Waveguide ◽  
Fourier Transform Spectrometer ◽  
Methane Detection

Design and experimental research on a visible-near infrared spatial modulating Fourier transform spectrometer based on micro multi-step mirrors

2014 ◽  
Vol 10 (3) ◽  
pp. 172-175 ◽  
Author(s):  
Yu-xin Qin ◽  
Jing-qiu Liang ◽  
Zhong-zhu Liang ◽  
Chao Tian ◽  
Jin-guang Lü ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Experimental Research ◽  
Near Infrared ◽  
Fourier Transform Spectrometer

scholarly journals Natural slab photonic crystals in centric diatoms

2019 ◽  
Author(s):  
Johannes W. Goessling ◽  
William P. Wardley ◽  
Martin Lopez Garcia
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
Spectral Range ◽  
Near Infrared ◽  
Light Regulation ◽  
Visible Spectral Range ◽  
Mating Strategies ◽  
Unit Cell ◽  
Critical Parameters ◽  
Centric Diatom

AbstractNatural photonic crystals can serve in mating strategies or as aposematism for animals, but they also exist in some photosynthetic organisms, with potential implications for their light regulation. Some of the most abundant microalgae, named diatoms, evolved a silicate exoskeleton, the frustule, perforated with ordered pores resembling photonic crystals. Here we present the first combined experimental and theoretical characterization of the photonic properties of the diatom girdle, i.e. one of two structures assembling the frustule. We show that the girdle of the centric diatom Coscinodiscus granii is a well-defined slab photonic crystal, causing, under more natural conditions when immersed in water, a pseudogap for modes in the near infrared. The pseudogap disperses towards the visible spectral range when light incides at larger angles. The girdle crystal structure facilitates in-plane propagation for modes in the green spectral range. We demonstrate that the period of the unit cell is one of the most critical factors for causing these properties. The period is shown to be similar within individuals of a long-term cultivated inbred line and between 4 different C. granii cell culture strains. In contrast, the pore diameter had negligible effects upon the photonic properties. We hence propose that critical parameters defining the photonic response of the girdle are highly preserved. Other centric diatom species, i.e. Thalasiosira pseudonana, C. radiatus and C. wailesii, present similar unit cell morphologies with various periods in their girdles. We speculate that evolution has preserved the photonic crystal character of the centric girdle, indicating an important biological functionality for this clade of diatoms.

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