scholarly journals Cavity Ring-Down Methane Sensor for Small Unmanned Aerial Systems

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 454 ◽  
Author(s):  
Benjamin Martinez ◽  
Thomas W. Miller ◽  
Azer P. Yalin
Keyword(s):  
Near Infrared ◽  
High Sensitivity ◽  
Unmanned Aerial Systems ◽  
Test Results ◽  
Methane Sensor ◽  
Open Path ◽  
Low Mass ◽  
Aerial Systems ◽  
High Finesse ◽  
Cavity Ring Down

We present the development, integration, and testing of an open-path cavity ring-down spectroscopy (CRDS) methane sensor for deployment on small unmanned aerial systems (sUAS). The open-path configuration used here (without pump or flow-cell) enables a low mass (4 kg) and low power (12 W) instrument that can be readily integrated to sUAS, defined here as having all-up mass of <25 kg. The instrument uses a compact telecom style laser at 1651 nm (near-infrared) and a linear 2-mirror high-finesse cavity. We show test results of flying the sensor on a DJI Matrice 600 hexacopter sUAS. The high sensitivity of the CRDS method allows sensitive methane detection with a precision of ~10–30 ppb demonstrated for actual flight conditions. A controlled release setup, where known mass flows are delivered, was used to simulate point-source methane emissions. Examples of methane plume detection from flight tests suggest that isolated plumes from sources with a mass flow as low as ~0.005 g/s can be detected. The sUAS sensor should have utility for emissions monitoring and quantification from natural gas infrastructure. To the best of our knowledge, it is also the first CRDS sensor directly deployed onboard an sUAS.

Magnetic fields of T Tauri stars and inner accretion discs

2018 ◽  
Vol 14 (A30) ◽  
pp. 121-121
Author(s):  
Jean-Francois Donati
Keyword(s):  
Magnetic Fields ◽  
Large Scale ◽  
Near Infrared ◽  
High Sensitivity ◽  
T Tauri Stars ◽  
Accretion Discs ◽  
High Resolution Spectroscopy ◽  
T Tauri ◽  
Low Mass ◽  
The Impact

AbstractMagnetic fields play a key role in the early life of stars and their planets, as they form from collapsing dense cores that progressively flatten into large-scale accretion discs and eventually settle as young suns orbited by planetary systems. Pre-main-sequence phases, in which central protostars feed from surrounding planet-forming accretion discs, are especially crucial for understanding how worlds like our Solar System are born.Magnetic fields of low-mass T Tauri stars (TTSs) are detected through high-resolution spectroscopy and spectropolarimetry (e.g., Johns Krull 2007), whereas their large-scale topologies can be inferred from time series of Zeeman signatures using tomographic techniques inspired from medical imaging (Donati & Landstreet 2009). Large-scale fields of TTSs are found to depend on the internal structure of the newborn star, allowing quantitative models of how TTSs magnetically interact with their inner accretion discs, and the impact of this interaction on the subsequent stellar evolution (e.g., Romanova et al. 2002, Zanni & Ferreira 2013).With its high sensitivity to magnetic fields, SPIRou, the new near-infrared spectropolarimeter installed in 2018 at CFHT (Donati et al. 2018), should yield new advances in the field, especially for young embedded class-I protostars, thereby bridging the gap with radio observations.

scholarly journals Bed topography of Jakobshavn Isbræ, Greenland, and Byrd Glacier, Antarctica

2014 ◽  
Vol 60 (223) ◽  
pp. 813-833 ◽  
Author(s):  
S. Gogineni ◽  
J.-B. Yan ◽  
J. Paden ◽  
C. Leuschen ◽  
J. Li ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Radar Data ◽  
Unmanned Aerial Systems ◽  
Music Algorithm ◽  
Bed Topography ◽  
Ice Surface ◽  
Elevation Data ◽  
Track Surface ◽  
Cross Track ◽  
Aerial Systems

AbstractThis paper presents the bed topography of Jakobshavn Isbræ, Greenland, and Byrd Glacier, Antarctica, derived from sounding these glaciers with high-sensitivity radars. To understand the processes causing the speed-up and retreat of outlet glaciers, and to enable the development of next-generation ice-sheet models, we need information on bed topography and basal conditions. To this end, we performed measurements with the progressively improved Multichannel Coherent Radar Depth Sounder/Imager (MCoRDS/I). We processed the data from each antenna-array element using synthetic aperture radar algorithms to improve radar sensitivity and reduce along-track surface clutter. We then applied array and image-processing algorithms to extract the weak bed echoes buried in off-vertical scatter (cross-track surface clutter). At Jakobshavn Isbræ, we observed 2.7 km thick ice ~30 km upstream of the calving front and ~850 m thick ice at the calving front. We also observed echoes from multiple interfaces near the bed. We applied the MUSIC algorithm to the data to derive the direction of arrival of the signals. This analysis revealed that clutter is dominated by the ice surface at Jakobshavn Isbræ. At Byrd Glacier, we found ~3.62 km thick ice, as well as a subglacial trench ~3.05 km below sea level. We used ice thickness information derived from radar data in conjunction with surface elevation data to generate bed maps for these two critical glaciers. The performance of current radars must be improved further by ~15 dB to fully sound the deepest part of Byrd Glacier. Unmanned aerial systems equipped with radars that can be flown over lines spaced as close as 5 m apart in the cross-track direction to synthesize a two-dimensional aperture would be ideal for collecting fine-resolution data over glaciers like Jakobshavn near their grounding lines.

scholarly journals Illumination Geometry and Flying Height Influence Surface Reflectance and NDVI Derived from Multispectral UAS Imagery

Drones ◽  
2019 ◽  
Vol 3 (3) ◽  
pp. 55 ◽  
Author(s):  
Daniel Stow ◽  
Caroline J. Nichol ◽  
Tom Wade ◽  
Jakob J. Assmann ◽  
Gillian Simpson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Vegetation Indices ◽  
Flying Height ◽  
Unmanned Aerial Systems ◽  
Radiometric Calibration ◽  
Very High Spatial Resolution ◽  
Vegetation Surveys ◽  
Solar Noon ◽  
Aerial Systems ◽  
Reflectance Measurements

Small unmanned aerial systems (UAS) have allowed the mapping of vegetation at very high spatial resolution, but a lack of standardisation has led to uncertainties regarding data quality. For reflectance measurements and vegetation indices (Vis) to be comparable between sites and over time, careful flight planning and robust radiometric calibration procedures are required. Two sources of uncertainty that have received little attention until recently are illumination geometry and the effect of flying height. This study developed methods to quantify and visualise these effects in imagery from the Parrot Sequoia, a UAV-mounted multispectral sensor. Change in illumination geometry over one day (14 May 2018) had visible effects on both individual images and orthomosaics. Average near-infrared (NIR) reflectance and NDVI in regions of interest were slightly lower around solar noon, and the contrast between shadowed and well-illuminated areas increased over the day in all multispectral bands. Per-pixel differences in NDVI maps were spatially variable, and much larger than average differences in some areas. Results relating to flying height were inconclusive, though small increases in NIR reflectance with height were observed over a black sailcloth tarp. These results underline the need to consider illumination geometry when carrying out UAS vegetation surveys.

Soil Moisture Retrievals from Unmanned Aerial Systems (UAS)

2020 ◽  
Author(s):  
ruodan zhuang ◽  
Salvatore Manfreda ◽  
Yijian Zeng ◽  
Zhongbo Su ◽  
Nunzio Romano ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Near Infrared ◽  
Spatial Scales ◽  
Standard Procedure ◽  
Thermal Inertia ◽  
Unmanned Aerial Systems ◽  
Natural Ecosystems ◽  
Resources Management ◽  
Cropland Area ◽  
Aerial Systems

&lt;p&gt;Quantification of the spatial and temporal behavior of soil moisture is vital for understanding water availability in agriculture, ecosystems research, river basin hydrology and water resources management. Unmanned Aerial Systems (UAS) offer a great potential in monitoring this parameter at sub-meter level and at relatively low cost. The standardization of operational procedures for soil moisture monitoring with UAS can be beneficial to understanding and quantify the quality of retrieved soil moisture (e.g., from different platforms and sensors).&lt;/p&gt;&lt;p&gt;In this study, soil moisture retrieved from UAS using different retrieval algorithms was compared to collocated ground measurements. The thermal inertia model builds upon the dependence of the thermal diffusion on soil moisture. The soil thermal inertia is quantified by processing visible and near-infrared (VIS-NIR) and thermal infrared (TIR) images, acquired at two different times of a day. The temperature&amp;#8211;vegetation trapezoidal model is also used to map soil moisture over vegetated pixels. This trapezoidal model depicts the soil moisture dependence of the surface energy balance. The comparison of the two algorithms helps define a preliminary standard procedure for retrieving soil moisture with UAS.&lt;/p&gt;&lt;p&gt;As a case study, a typical cropland area with olive orchard, cherry and walnut trees in the region of Monteforte Cilento (Italy, Salerno) is used, where optical and thermal images and in situ data were simultaneously acquired. In the Alento observatory, long-term studies on vadose zone hydrology have been conducting across a range of spatial scales. Our findings provide an important contribution towards improving our knowledge on evaluating the ability of UAS to map soil moisture, in support of sustainable natural resources management and climate change studies.&lt;/p&gt;&lt;p&gt;This research is a part of EU COST-Action &amp;#8220;HARMONIOUS: Harmonization of UAS techniques for agricultural and natural ecosystems monitoring&amp;#8221;.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords:&lt;/strong&gt; soil moisture, Unmanned Aerial Systems, thermal inertia, HARMONIOUS&lt;/p&gt;

scholarly journals Lightweight mid-infrared methane sensor for unmanned aerial systems

2017 ◽  
Vol 123 (6) ◽  
Author(s):  
Levi M. Golston ◽  
Lei Tao ◽  
Caroline Brosy ◽  
Klaus Schäfer ◽  
Benjamin Wolf ◽  
...  
Keyword(s):  
Unmanned Aerial Systems ◽  
Mid Infrared ◽  
Methane Sensor ◽  
Aerial Systems

A near-infrared C2H2/CH4 dual-gas sensor system combining off-axis integrated-cavity output spectroscopy and frequency-division-multiplexing-based wavelength modulation spectroscopy

The Analyst ◽  
2019 ◽  
Vol 144 (6) ◽  
pp. 2003-2010 ◽  
Author(s):  
Kaiyuan Zheng ◽  
Chuantao Zheng ◽  
Dan Yao ◽  
Lien Hu ◽  
Zidi Liu ◽  
...  
Keyword(s):  
Near Infrared ◽  
High Sensitivity ◽  
Dynamic Measurement ◽  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Frequency Division ◽  
Modulation Spectroscopy ◽  
Cavity Output ◽  
High Finesse ◽  
High Finesse Cavity

A near-infrared C2H2/CH4 sensor was demonstrated utilizing a miniaturized high finesse cavity with high sensitivity and remarkable dynamic measurement performance.

scholarly journals Non-Invasive Tools to Detect Smoke Contamination in Grapevine Canopies, Berries and Wine: A Remote Sensing and Machine Learning Modeling Approach

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3335 ◽  
Author(s):  
Sigfredo Fuentes ◽  
Eden Jane Tongson ◽  
Roberta De Bei ◽  
Claudia Gonzalez Viejo ◽  
Renata Ristic ◽  
...  
Keyword(s):  
Machine Learning ◽  
Pattern Recognition ◽  
Management Practices ◽  
Near Infrared ◽  
Detection System ◽  
Screening Tools ◽  
Unmanned Aerial Systems ◽  
Non Invasive ◽  
Aerial Systems ◽  
Non Destructive

Bushfires are becoming more frequent and intensive due to changing climate. Those that occur close to vineyards can cause smoke contamination of grapevines and grapes, which can affect wines, producing smoke-taint. At present, there are no available practical in-field tools available for detection of smoke contamination or taint in berries. This research proposes a non-invasive/in-field detection system for smoke contamination in grapevine canopies based on predictable changes in stomatal conductance patterns based on infrared thermal image analysis and machine learning modeling based on pattern recognition. A second model was also proposed to quantify levels of smoke-taint related compounds as targets in berries and wines using near-infrared spectroscopy (NIR) as inputs for machine learning fitting modeling. Results showed that the pattern recognition model to detect smoke contamination from canopies had 96% accuracy. The second model to predict smoke taint compounds in berries and wine fit the NIR data with a correlation coefficient (R) of 0.97 and with no indication of overfitting. These methods can offer grape growers quick, affordable, accurate, non-destructive in-field screening tools to assist in vineyard management practices to minimize smoke taint in wines with in-field applications using smartphones and unmanned aerial systems (UAS).

scholarly journals 3D Calibration Test-Field for Digital Cameras Mounted on Unmanned Aerial Systems (UAS)

2018 ◽  
Vol 10 (12) ◽  
pp. 2017 ◽  
Author(s):  
Valeria-Ersilia Oniga ◽  
Norbert Pfeifer ◽  
Ana-Maria Loghin
Keyword(s):  
Near Infrared ◽  
Low Cost ◽  
Digital Camera ◽  
Field Measurements ◽  
Unmanned Aerial Systems ◽  
Test Field ◽  
Digital Cameras ◽  
Self Calibration ◽  
Technological Developments ◽  
Aerial Systems

Due to the large number of technological developments in recent years, UAS systems are now used for monitoring purposes and in projects with high precision demand, such as 3D model-based creation of dams, reservoirs, historical monuments etc. These unmanned systems are usually equipped with an automatic pilot device and a digital camera (photo/video, multispectral, Near Infrared etc.), of which the lens has distortions; but this can be determined in a calibration process. Currently, a method of “self-calibration” is used for the calibration of the digital cameras mounted on UASs, but, by using the method of calibration based on a 3D calibration object, the accuracy is improved in comparison with other methods. Thus, this paper has the objective of establishing a 3D calibration field for the digital cameras mounted on UASs in terms of accuracy and robustness, being the largest reported publication to date. In order to test the proposed calibration field, a digital camera mounted on a low-cost UAS was calibrated at three different heights: 23 m, 28 m, and 35 m, using two configurations for image acquisition. Then, a comparison was made between the residuals obtained for a number of 100 Check Points (CPs) using self-calibration and test-field calibration, while the number of Ground Control Points (GCPs) variedand the heights were interchanged. Additionally, the parameters where tested on an oblique flight done 2 years before calibration, in manual mode at a medium altitude of 28 m height. For all tests done in the case of the double grid nadiral flight, the parameters calculated with the proposed 3D field improved the results by more than 50% when using the optimum and a large number of GCPs, and in all analyzed cases with 75% to 95% when using a minimum of 3 GCP. In this context, it is necessary to conduct accurate calibration in order to increase the accuracy of the UAS projects, and also to reduce field measurements.

scholarly journals Open-path cavity ring-down methane sensor for mobile monitoring of natural gas emissions

2019 ◽  
Vol 27 (14) ◽  
pp. 20084 ◽  
Author(s):  
Laura E. Mchale ◽  
Benjamin Martinez ◽  
Thomas W. Miller ◽  
Azer P. Yalin
Keyword(s):  
Natural Gas ◽  
Mobile Monitoring ◽  
Gas Emissions ◽  
Methane Sensor ◽  
Open Path ◽  
Natural Gas Emissions ◽  
Cavity Ring Down
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