Reflectance characteristics of cumulative defoliation of balsam fir

1988 ◽  
Vol 18 (8) ◽  
pp. 1008-1016 ◽  
Author(s):  
D. G. Leckie ◽  
P. M. Teillet ◽  
G. Fedosejevs ◽  
D. P. Ostaff
Keyword(s):  
Near Infrared ◽  
Spectral Characteristics ◽  
Broad Band ◽  
Integrating Sphere ◽  
Simple Relationship ◽  
Spectral Bands ◽  
Infrared Wavelengths ◽  
Remote Sensing Techniques ◽  
Middle Infrared ◽  
Airborne Sensors

Knowledge of the spectral characteristics of trees with varying degrees of needle loss is essential for developing remote sensing techniques for assessing defoliation. Spectra covering the range 400–2400 nm were acquired for single tree crowns suffering varying degrees of cumulative defoliation due to the spruce budworm (Choristoneurafumiferana (Clem.)), using a spectrometer mounted in the bucket of a boom truck. Spectra over the range 360–1100 nm were also obtained for the components of defoliated trees (i.e., needles, bare branches, and lichen), using a separate spectrometer and integrating sphere. Estimates of defoliation symptoms of each tree were made from the ground and above the tree. Changes in reflectance had a close and simple relationship with the defoliation symptoms measured. The spectral differences due to cumulative defoliation that were observed were broad-band features. The best spectral regions for differentiating levels of cumulative defoliation symptoms were the blue, red, shorter near-infrared wavelengths, and middle-infrared. Although currently available satellite and airborne sensors operate in these spectral regions, defoliation assessment may be improved by the use of optimized spectral bands.

Spectral characteristics of leafy spurge (Euphorbia esula) leaves and flower bracts

Weed Science ◽  
2004 ◽  
Vol 52 (4) ◽  
pp. 492-497 ◽  
Author(s):  
E. Raymond Hunt ◽  
James E. McMurtrey ◽  
Amy E. Parker Williams ◽  
Lawrence A. Corp
Keyword(s):  
Remote Sensing ◽  
High Performance ◽  
Near Infrared ◽  
Spectral Characteristics ◽  
Leafy Spurge ◽  
Hyperspectral Remote Sensing ◽  
Total Carotenoids ◽  
Physiological Basis ◽  
Infrared Wavelengths ◽  
Pigment Concentrations

Leafy spurge can be detected during flowering with either aerial photography or hyperspectral remote sensing because of the distinctive yellow-green color of the flower bracts. The spectral characteristics of flower bracts and leaves were compared with pigment concentrations to determine the physiological basis of the remote sensing signature. Compared with leaves of leafy spurge, flower bracts had lower reflectance at blue wavelengths (400 to 500 nm), greater reflectance at green, yellow, and orange wavelengths (525 to 650 nm), and approximately equal reflectances at 680 nm (red) and at near-infrared wavelengths (725 to 850 nm). Pigments from leaves and flower bracts were extracted in dimethyl sulfoxide, and the pigment concentrations were determined spectrophotometrically. Carotenoid pigments were identified using high-performance liquid chromatography. Flower bracts had 84% less chlorophylla, 82% less chlorophyllb, and 44% less total carotenoids than leaves, thus absorptance by the flower bracts should be less and the reflectance should be greater at blue and red wavelengths. The carotenoid to chlorophyll ratio of the flower bracts was approximately 1:1, explaining the hue of the flower bracts but not the value of reflectance. The primary carotenoids were lutein, β-carotene, and β-cryptoxanthin in a 3.7:1.5:1 ratio for flower bracts and in a 4.8:1.3:1 ratio for leaves, respectively. There was 10.2 μg g−1fresh weight of colorless phytofluene present in the flower bracts and none in the leaves. The fluorescence spectrum indicated high blue, red, and far-red emission for leaves compared with flower bracts. Fluorescent emissions from leaves may contribute to the higher apparent leaf reflectance in the blue and red wavelength regions. The spectral characteristics of leafy spurge are important for constructing a well-documented spectral library that could be used with hyperspectral remote sensing.

scholarly journals The Value of Sentinel-2 Spectral Bands for the Assessment of Winter Wheat Growth and Development

2019 ◽  
Vol 11 (17) ◽  
pp. 2050 ◽  
Author(s):  
Andrew Revill ◽  
Anna Florence ◽  
Alasdair MacArthur ◽  
Stephen Hoad ◽  
Robert Rees ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Chlorophyll Content ◽  
Management Practices ◽  
Near Infrared ◽  
Spectral Characteristics ◽  
Crop Management ◽  
Area Index ◽  
Spectral Bands ◽  
The Mean ◽  
Sentinel 2

Leaf Area Index (LAI) and chlorophyll content are strongly related to plant development and productivity. Spatial and temporal estimates of these variables are essential for efficient and precise crop management. The availability of open-access data from the European Space Agency’s (ESA) Sentinel-2 satellite—delivering global coverage with an average 5-day revisit frequency at a spatial resolution of up to 10 metres—could provide estimates of these variables at unprecedented (i.e., sub-field) resolution. Using synthetic data, past research has demonstrated the potential of Sentinel-2 for estimating crop variables. Nonetheless, research involving a robust analysis of the Sentinel-2 bands for supporting agricultural applications is limited. We evaluated the potential of Sentinel-2 data for retrieving winter wheat LAI, leaf chlorophyll content (LCC) and canopy chlorophyll content (CCC). In coordination with destructive and non-destructive ground measurements, we acquired multispectral data from an Unmanned Aerial Vehicle (UAV)-mounted sensor measuring key Sentinel-2 spectral bands (443 to 865 nm). We applied Gaussian processes regression (GPR) machine learning to determine the most informative Sentinel-2 bands for retrieving each of the variables. We further evaluated the GPR model performance when propagating observation uncertainty. When applying the best-performing GPR models without propagating uncertainty, the retrievals had a high agreement with ground measurements—the mean R2 and normalised root-mean-square error (NRMSE) were 0.89 and 8.8%, respectively. When propagating uncertainty, the mean R2 and NRMSE were 0.82 and 11.9%, respectively. When accounting for measurement uncertainty in the estimation of LAI and CCC, the number of most informative Sentinel-2 bands was reduced from four to only two—the red-edge (705 nm) and near-infrared (865 nm) bands. This research demonstrates the value of the Sentinel-2 spectral characteristics for retrieving critical variables that can support more sustainable crop management practices.

scholarly journals Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life

2015 ◽  
Vol 112 (13) ◽  
pp. 3886-3891 ◽  
Author(s):  
Siddharth Hegde ◽  
Ivan G. Paulino-Lima ◽  
Ryan Kent ◽  
Lisa Kaltenegger ◽  
Lynn Rothschild
Keyword(s):  
Near Infrared ◽  
Spectral Characteristics ◽  
Extreme Environments ◽  
Electromagnetic Spectrum ◽  
Extraterrestrial Life ◽  
Remote Sensing Techniques ◽  
The One ◽  
Cellular Water ◽  
Life On Earth ◽  
Rocky Planets

Exoplanet discovery has made remarkable progress, with the first rocky planets having been detected in the central star’s liquid water habitable zone. The remote sensing techniques used to characterize such planets for potential habitability and life rely solely on our understanding of life on Earth. The vegetation red edge from terrestrial land plants is often used as a direct signature of life, but it occupies only a small niche in the environmental parameter space that binds life on present-day Earth and has been widespread for only about 460 My. To more fully exploit the diversity of the one example of life known, we measured the spectral characteristics of 137 microorganisms containing a range of pigments, including ones isolated from Earth’s most extreme environments. Our database covers the visible and near-infrared to the short-wavelength infrared (0.35–2.5 µm) portions of the electromagnetic spectrum and is made freely available from biosignatures.astro.cornell.edu. Our results show how the reflectance properties are dominated by the absorption of light by pigments in the visible portion and by strong absorptions by the cellular water of hydration in the infrared (up to 2.5 µm) portion of the spectrum. Our spectral library provides a broader and more realistic guide based on Earth life for the search for surface features of extraterrestrial life. The library, when used as inputs for modeling disk-integrated spectra of exoplanets, in preparation for the next generation of space- and ground-based instruments, will increase the chances of detecting life.

An infrared spectroscopic study of hydrogen feldspar (HA1Si3O8)

1995 ◽  
Vol 59 (394) ◽  
pp. 15-24 ◽  
Author(s):  
H. Behrens ◽  
G. Müller
Keyword(s):  
Amorphous Phase ◽  
Near Infrared ◽  
Complex Structure ◽  
Broad Band ◽  
Molecular Water ◽  
Hydroxyl Groups ◽  
Infrared Spectroscopic Study ◽  
Absorption Bands ◽  
Two Phases ◽  
Middle Infrared

AbstractHydrogen in H-feldspar obtained by ion-exchange was studied in the spectral range 1000–5500 cm−1 by single crystal IR microspectroscopy. Spectra were almost identical for H-feldspars prepared either from sanidine or from adularia. Two bands in the middle-infrared were identified by D/H exchange as OH vibration modes. One broad band with a maximum at 3000 cm−1 and shoulders at 2800, 3200 and 3500 cm−1 confirms previous work. An additional OH absorption band with a maximum at 2485 cm−1 was observed for the first time in feldspars. The pleochroism of the OH absorption bands suggests that the H-feldspar is composed of two phases, an amorphous phase and a feldspathic phase. The proportion of the amorphous phase is increased by heating, producing a shift of the maximum of the band at 3000 cm−1 towards higher wavenumber and a decrease of the intensity of the band at 2485 cm−1. Near-infrared spectroscopy showed that hydrogen is present as hydroxyl groups bound to tetrahedral cations in both phases. Molecular water was not detected. The experimental results imply that hydrogen is incorporated in the H-feldspars as protons attached to bridging oxygen as well as to non-bridging oxygen. The complex structure of the IR spectra implies that the protons are distributed over a large number of sites in the cation cavity of the feldspars.

scholarly journals Optical and Near Infrared Observations of Post-AGB Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 383-383
Author(s):  
T. Fujii ◽  
T. Ono ◽  
Y. Nakada ◽  
M. Parthasarathy
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
Agb Stars ◽  
Ir Camera ◽  
Infrared Observations ◽  
Infrared Wavelengths ◽  
Band Spectra

The post-AGB stars rapidly change their spectral energy distribution on their way from the asymptotic giant branch(AGB) to planetary nebula stage. They are generally surrounded by cool and extended dust shells emitting largely in the infrared wavelengths. A selected sample of the post-AGB candidates were observed using the CCDand IR camera at Kiso and Nishi-Harima Astronomical Observatory. They were classified based on their broad band spectra from B to K’ band and their evolutionary stages have been discussed using the simple model of the dust shell around a star. The light variation of some of these objects were monitored and their light curves are also presented.

scholarly journals Electromechanically reconfigurable optical nano-kirigami

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shanshan Chen ◽  
Zhiguang Liu ◽  
Huifeng Du ◽  
Chengchun Tang ◽  
Chang-Yin Ji ◽  
...  
Keyword(s):  
Near Infrared ◽  
Large Range ◽  
Three Dimensional ◽  
High Contrast ◽  
Si Substrate ◽  
High Modulation ◽  
Gold Nanostructure ◽  
Infrared Wavelengths ◽  
On Chip ◽  
Nano Electromechanical System

AbstractKirigami, with facile and automated fashion of three-dimensional (3D) transformations, offers an unconventional approach for realizing cutting-edge optical nano-electromechanical systems. Here, we demonstrate an on-chip and electromechanically reconfigurable nano-kirigami with optical functionalities. The nano-electromechanical system is built on an Au/SiO2/Si substrate and operated via attractive electrostatic forces between the top gold nanostructure and bottom silicon substrate. Large-range nano-kirigami like 3D deformations are clearly observed and reversibly engineered, with scalable pitch size down to 0.975 μm. Broadband nonresonant and narrowband resonant optical reconfigurations are achieved at visible and near-infrared wavelengths, respectively, with a high modulation contrast up to 494%. On-chip modulation of optical helicity is further demonstrated in submicron nano-kirigami at near-infrared wavelengths. Such small-size and high-contrast reconfigurable optical nano-kirigami provides advanced methodologies and platforms for versatile on-chip manipulation of light at nanoscale.

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