scholarly journals Multi-Channel Optical Receiver for Ground-Based Topographic Hyperspectral Remote Sensing

2019 ◽  
Vol 11 (5) ◽  
pp. 578 ◽  
Author(s):  
Sean Salazar ◽  
Richard Coffman
Keyword(s):  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Absorption Spectrometry ◽  
Optical Receiver ◽  
Infrared Range ◽  
Receiver Design ◽  
Remote Sensor ◽  
Rapid Characterization ◽  
Shortwave Infrared

Receiver design is integral to the development of a new remote sensor. An effective receiver delivers backscattered light to the detector while optimizing the signal-to-noise ratio at the desired wavelengths. Towards the goal of effective receiver design, a multi-channel optical receiver was developed to collect range-resolved, backscattered energy for simultaneous hyperspectral and differential absorption spectrometry (LAS) measurements. The receiver is part of a new, ground-based, multi-mode lidar instrument for remote characterization of soil properties. The instrument, referred to as the soil observation laser absorption spectrometer (SOLAS), was described previously in the literature. A detailed description of the multi-channel receiver of the SOLAS is presented herein. The hyperspectral channel receives light across the visible near-infrared (VNIR) to shortwave infrared (SWIR) spectrum (350–2500 nm), while the LAS channel was optimized for detection in a narrower portion of the near-infrared range (820–850 nm). The range-dependent field of view for each channel is presented and compared with the beam evolution of the SOLAS instrument transmitter. Laboratory-based testing of each of the receiver channels was performed to determine the effectiveness of the receiver. Based on reflectance spectra collected for four soil types, at distances of 20, 35, and 60 m from the receiver, reliable hyperspectral measurements were gathered, independent of the range to the target. Increased levels of noise were observed at the edges of the VNIR and SWIR detector ranges, which were attributed to the lack of sensitivity of the instrument in these regions. The suitability of the receiver design, for the collection of both hyperspectral and LAS measurements at close-ranges, is documented herein. Future development of the instrument will enable the combination of long-range, ground-based hyperspectral measurements with the LAS measurements to correct for absorption, due to atmospheric water vapor. The envisioned application for the instrument includes the rapid characterization of bare or vegetated soils and minerals, such as are present in mine faces and tailings, or unstable slopes.

scholarly journals A study of synthetic <sup>13</sup>CH<sub>4</sub> retrievals from TROPOMI and Sentinel-5/UVNS

2019 ◽  
Vol 12 (12) ◽  
pp. 6273-6301
Author(s):  
Edward Malina ◽  
Haili Hu ◽  
Jochen Landgraf ◽  
Ben Veihelmann
Keyword(s):  
Near Infrared ◽  
Signal To Noise Ratio ◽  
A Priori ◽  
Ultra Violet ◽  
High Signal ◽  
Atmospheric Methane ◽  
Δ13c Values ◽  
Temporal Averaging ◽  
A Minor ◽  
Shortwave Infrared

Abstract. Retrievals of methane isotopologues have the potential to differentiate between natural and anthropogenic methane sources types, which can provide much needed information about the current global methane budget. We investigate the feasibility of retrieving the second most abundant isotopologue of atmospheric methane (13CH4, roughly 1.1 % of total atmospheric methane) from the shortwave infrared (SWIR) channels of the future Sentinel-5/ultra-violet, visible, near-infrared, shortwave infrared (UVNS) and current Copernicus Sentinel-5 Precursor TROPOspheric Monitoring Instrument (TROPOMI) instruments. With the intended goal of calculating the δ13C value, we assume that a δ13C uncertainty of better than 1 ‰ is sufficient to differentiate between source types, which corresponds to a 13CH4 uncertainty of <0.02 ppb. Using the well-established information content analysis techniques and assuming clear-sky, non-scattering conditions, we find that the SWIR3 (2305–2385 nm) channel on the TROPOMI instrument can achieve a mean uncertainty of <1 ppb, while the SWIR1 channel (1590–1675 nm) on the Sentinel-5 UVNS instrument can achieve <0.68 ppb or <0.2 ppb in high signal-to-noise ratio (SNR) cases. These uncertainties combined with significant spatial and/or temporal averaging techniques can reduce δ13C uncertainty to the target magnitude or better. However, we find that 13CH4 retrievals are highly sensitive to errors in a priori knowledge of temperature and pressure, and accurate knowledge of these profiles is required before 13CH4 retrievals can be performed on TROPOMI and future Sentinel-5/UVNS data. In addition, we assess the assumption that scattering-induced light path errors are cancelled out by comparing the δ13C values calculated for non-scattering and scattering scenarios. We find that there is a minor bias in δ13C values from scattering and non-scattering retrievals, but this is unrelated to scattering-induced errors.

scholarly journals Quantitative Characterization of Arnicae flos by RP-HPLC-UV and NIR Spectroscopy

Foods ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 9
Author(s):  
Daniela Ivanova ◽  
Vera Deneva ◽  
Dimitrina Zheleva-Dimitrova ◽  
Vesela Balabanova-Bozushka ◽  
Daniela Nedeltcheva ◽  
...  
Keyword(s):  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Sesquiterpene Lactones ◽  
Nir Spectroscopy ◽  
Spectral Distortion ◽  
Active Components ◽  
Quantitative Characterization ◽  
Convolution Window ◽  
Spectra Processing

The possibility of applying near-infrared (NIR) spectroscopy to monitor 13 active components (phenolic acids, flavonoids, and sesquiterpene lactones) in Arnicae flos was studied. The preprocessing of the spectra were performed by using the conventional Golay-Savitzky procedure and the newly developed step-by-step filter. The results obtained show that the step-by-step filter derivatives provide a better signal-to-noise ratio at a lower convolution window. Better calibration for the content of protocatechuic acid, chlorogenic acid, caffeic acid, p-cumaric acid, ferulic acid, isoquercitrin, and quercetin were obtained by step-by-step filter derivatives, compared to the direct raw spectra processing and the Golay-Savitzky approach. Although the step-by-step filter substantially reduces the spectral distortion, the convolution procedure leads to loss of spectral points in the red end of the spectral curve. Probably for this reason this approach shows better calibration only in seven of the monitored 13 active components.

scholarly journals Rapid Characterization of Fatty Acids in Oleaginous Microalgae by Near-Infrared Spectroscopy

2015 ◽  
Vol 16 (12) ◽  
pp. 7045-7056 ◽  
Author(s):  
Bin Liu ◽  
Jin Liu ◽  
Tianpeng Chen ◽  
Bo Yang ◽  
Yue Jiang ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Oleaginous Microalgae ◽  
Rapid Characterization

scholarly journals Searching for the near-infrared counterpart of Proxima c using multi-epoch high-contrast SPHERE data at VLT

2020 ◽  
Vol 638 ◽  
pp. A120 ◽  
Author(s):  
R. Gratton ◽  
A. Zurlo ◽  
H. Le Coroller ◽  
M. Damasso ◽  
F. Del Sordo ◽  
...  
Keyword(s):  
Near Infrared ◽  
Planetary System ◽  
Orbital Motion ◽  
Signal To Noise Ratio ◽  
Orbital Plane ◽  
Radial Velocities ◽  
Random Fluctuation ◽  
Direct Imaging ◽  
Imaging Detection

Context. Proxima Centauri is the closest star to the Sun and it is known to host an Earth-like planet in its habitable zone; very recently a second candidate planet was proposed based on radial velocities. At quadrature, the expected projected separation of this new candidate is larger than 1 arcsec, making it a potentially interesting target for direct imaging. Aims. While identification of the optical counterpart of this planet is expected to be very difficult, successful identification would allow for a detailed characterization of the closest planetary system. Methods. We searched for a counterpart in SPHERE images acquired over four years through the SHINE survey. In order to account for the expected large orbital motion of the planet, we used a method that assumes the circular orbit obtained from radial velocities and exploits the sequence of observations acquired close to quadrature in the orbit. We checked this with a more general approach that considers Keplerian motion, called K-stacker. Results. We did not obtain a clear detection. The best candidate has signal-to-noise ratio (S∕N) = 6.1 in the combined image. A statistical test suggests that the probability that this detection is due to random fluctuation of noise is <1%, but this result depends on the assumption that the distribution of noise is uniform over the image, a fact that is likely not true. The position of this candidate and the orientation of its orbital plane fit well with observations in the ALMA 12 m array image. However, the astrometric signal expected from the orbit of the candidate we detected is 3σ away from the astrometric motion of Proxima as measured from early Gaia data. This, together with the unexpectedly high flux associated with our direct imaging detection, means we cannot confirm that our candidate is indeed Proxima c. Conclusions. On the other hand, if confirmed, this would be the first observation in imaging of a planet discovered from radial velocities and the second planet (after Fomalhaut b) of reflecting circumplanetary material. Further confirmation observations should be done as soon as possible.

scholarly journals Anisometric Ln(III) Complexes with Efficient Near-IR Luminescence

Inorganics ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 9
Author(s):  
Andrey A. Knyazev ◽  
Aleksandr S. Krupin ◽  
Yuriy G. Galyametdinov
Keyword(s):  
Near Infrared ◽  
Emission Spectra ◽  
Structural Features ◽  
Infrared Range ◽  
Light Emitting ◽  
Near Ir ◽  
Re Elements ◽  
Stokes Shifts ◽  
Narrow Emission

Recent studies in development of near-infrared luminophores focus on overcoming their disadvantages such as low quantum efficiency, limited emission power, and broad emission spectra. Rare earth (RE) elements are promising compounds in this respect as they offer a unique set of optical properties that provide narrow emission spectra and large Stokes shifts. This work reports the results of synthesis and characterization of new anisometric complexes of lanthanide(III) tris(b-diketonates) and 1,10-phenanthroline. These complexes possess light emitting-properties in the near-infrared range. Due to their structural features, these complexes allow production of homogeneous films by spin coating. These films are transparent in the visible and near-infrared ranges (transmission up to 99%). This paper demonstrates advantages of Yb(III), Er(III), and Nd(III) complexes as potential components of highly efficient light-transforming NIR coatings.

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