scholarly journals Weak spectral features on (101995) Bennu from the OSIRIS-REx Visible and InfraRed Spectrometer

2020 ◽  
Vol 644 ◽  
pp. A148 ◽  
Author(s):  
A. A. Simon ◽  
H. H. Kaplan ◽  
E. Cloutis ◽  
V. E. Hamilton ◽  
C. Lantz ◽  
...  
Keyword(s):  
Iron Oxides ◽  
Surface Shape ◽  
Spectral Features ◽  
Absorption Bands ◽  
Weak Absorption ◽  
Spectral Interpretation ◽  
Average Spectrum ◽  
Resource Identification ◽  
Infrared Spectrometer ◽  
Compositional Variations

Context. The NASA Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission has obtained thousands of spectra of asteroid (101955) Bennu with the OSIRIS-REx Visible and InfraRed Spectrometer. Aims. We present a spectral search for minor absorption bands and determine compositional variations on the surface of Bennu. Methods. Reflectance spectra with low and high spatial resolutions were analyzed for evidence of weak absorption bands. Spectra were also divided by a global average spectrum to isolate unique spectral features, and variations in the strongest band depths were mapped on a surface shape model. The global visible to near-IR spectrum of Bennu shows evidence of several weak absorption bands with depths of a few percent. Results. Several observed bands are consistent with phyllosilicates, and their distribution correlates with the stronger 2.74-μm hydration band. A 0.55-μm band is consistent with iron oxides and is deepest in the spectrally reddest areas on Bennu. The presence of hydrated phyllosilicates and iron oxides indicates substantial aqueous alteration in Bennu’s past. Conclusions. Bennu’s spectra are not identical to a limited set of carbonaceous chondrite spectra, possibly due to compositional properties and spatial scale differences; however, returned samples should contain a mixture of common chondrite materials.

scholarly journals In-Flight Calibration and Performance of the OSIRIS-REx Visible and IR Spectrometer (OVIRS)

2018 ◽  
Vol 10 (9) ◽  
pp. 1486 ◽  
Author(s):  
Amy Simon ◽  
Dennis Reuter ◽  
Nicolas Gorius ◽  
Allen Lunsford ◽  
Richard Cosentino ◽  
...  
Keyword(s):  
Radiometric Calibration ◽  
Atmospheric Models ◽  
Ground Testing ◽  
Spectral Interpretation ◽  
Resource Identification ◽  
Infrared Spectrometer ◽  
Visible Wavelengths ◽  
And Performance ◽  
One Year ◽  
Better Than

Performance of the Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS-REx) Visible and InfraRed Spectrometer (OVIRS) instrument was validated, showing that it met all science requirements during extensive thermal vacuum ground testing. Preliminary instrument radiometric calibration coefficients and wavelength mapping were also determined before instrument delivery and launch using NIST-traceable sources. One year after launch, Earth flyby data were used to refine the wavelength map by comparing OVIRS spectra with atmospheric models. Near-simultaneous data from other Earth-orbiting satellites were used to cross-calibrate the OVIRS absolute radiometric response, particularly at visible wavelengths. Trending data from internal calibration sources and the Sun show that instrument radiometric performance has been stable to better than 1% in the 18 months since launch.

scholarly journals PHOTOGRAMMETRIC PROCESSING OF OSIRIS-REX IMAGES OF ASTEROID (101955) BENNU

2020 ◽  
Vol V-3-2020 ◽  
pp. 587-594
Author(s):  
K. L. Edmundson ◽  
K. J. Becker ◽  
T. L. Becker ◽  
C. A. Bennett ◽  
D. N. DellaGiustina ◽  
...  
Keyword(s):  
Control Process ◽  
Laser Altimeter ◽  
Shape Models ◽  
Spectral Interpretation ◽  
Global Mapping ◽  
Resource Identification ◽  
Imaging Sensors ◽  
Future Work ◽  
Selection Of ◽  
Reconnaissance Surveys

Abstract. The principal objective of the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission is to retrieve a sample of the asteroid (101955) Bennu and return it to Earth. OSIRIS-REx arrived at Bennu in December 2018. Images of the asteroid by the OSIRIS-REx Camera Suite (OCAMS) were photogrammetrically controlled to produce a global basemap and site-specific image mosaics essential to the selection of a primary and backup sample site, which were announced in December 2019. In the control process, OCAMS images were registered to shape models created from OSIRIS-REx Laser Altimeter (OLA) data and from the process of stereophotoclinometry. This paper summarizes the photogrammetric control to date of images collected at Bennu. We briefly review the mission and the OCAMS imaging sensors. We then describe the photogrammetric control process for the global mapping campaign and targeted reconnaissance surveys of candidate sample sites. Finally, we discuss ongoing and future work.

scholarly journals Electron Dynamics in Anatase TiO2 Nanoparticles by Ultrafast Broadband Deep-Ultraviolet Spectroscopy

2019 ◽  
Vol 205 ◽  
pp. 05017
Author(s):  
Edoardo Baldini ◽  
Tania Palmieri ◽  
Enrico Pomarico ◽  
Gerald Auböck ◽  
Majed Chergui
Keyword(s):  
Lattice Dynamics ◽  
Anatase Tio2 ◽  
Spectral Features ◽  
Electron Dynamics ◽  
Electron Cooling ◽  
Absorption Bands ◽  
Bulk Absorption ◽  
Anatase Nanoparticles ◽  
Deep Ultraviolet ◽  
Broadband Spectroscopy

The optical bandgap of anatase TiO2 nanoparticles is dominated by bulk absorption bands in the deep-ultraviolet due to strongly bound excitons. These spectral features can be utilized as a sensitive probe of carrier and lattice dynamics inside the TiO2 nanoparticles. Here, we implement ultrafast broadband spectroscopy tuned to the exciton resonances in order to track the electron cooling in the conduction band of bare anatase nanoparticles and monitor the electron injection dynamics from an external dye in the case of sensitized anatase nanoparticles.

scholarly journals The mid-infrared spectral characteristics of blazars

2014 ◽  
Vol 10 (S313) ◽  
pp. 93-94
Author(s):  
Howard A. Smith ◽  
F. Massaro ◽  
R. D'Abrusco ◽  
A. Paggi ◽  
P. Cowperthwaite ◽  
...  
Keyword(s):  
Large Fraction ◽  
Spectral Characteristics ◽  
Continuum Emission ◽  
Spectral Features ◽  
Mid Infrared ◽  
Infrared Spectral ◽  
Infrared Spectrometer ◽  
Γ Ray ◽  
Followup Studies ◽  
The Continuum

AbstractWe previously reported discovering that blazars have distinctive infrared colors as seen in the WISE mission. Of particular note are γ-ray blazars, the locus of whose colors roughly overlaps with QSOs contours but which is more tightly delimited and bluer than ULIRGs and Seyferts. Since a large fraction of γ-ray sources are unassociated with any point source, but are expected to be blazars, identifying a WISE-candidate blazar in the γ-ray source field enables efficient followup studies. In an effort to better understand why blazars have these colors, we reduced and analyzed Spitzer Infrared Spectrometer (IRS) measurements on 73 blazars of varying types, some at several epochs. These spectra can be used to study the continuum emission (non-thermal), and search for atomic or other spectral features.

Detection of two interstellar absorption bands coincident with spectral features of C60+

Nature ◽  
1994 ◽  
Vol 369 (6478) ◽  
pp. 296-298 ◽  
Author(s):  
B. H. Foing ◽  
P. Ehrenfreund
Keyword(s):  
Spectral Features ◽  
Absorption Bands ◽  
Interstellar Absorption

scholarly journals Diurnal variation of midlatitudinal NO<sub>3</sub> column abundance over Table Mountain Facility, California

2010 ◽  
Vol 10 (8) ◽  
pp. 20193-20237
Author(s):  
C. M. Chen ◽  
R. P. Cageao ◽  
L. Lawrence ◽  
J. Stutz ◽  
R. J. Salawitch ◽  
...  
Keyword(s):  
Full Moon ◽  
Optical Absorption Spectroscopy ◽  
Spectral Features ◽  
Free Troposphere ◽  
Absorption Bands ◽  
Model Calculations ◽  
Diurnal Variability ◽  
One Dimensional ◽  
Lunar Occultation ◽  
Table Mountain

Abstract. The column abundance of NO3 was measured over Table Mountain Facility, CA (34.4° N, 117.7° W) from May 2003 through September 2004, using lunar occultation near full moon with a grating spectrometer. The NO3 column retrieval was performed with the differential optical absorption spectroscopy (DOAS) technique using both the 623 and 662 nm NO3 absorption bands. Other spectral features such as Fraunhofer lines and absorption from water vapor and oxygen were removed using solar spectra obtained at different airmass factors. We observed a seasonal variation, with nocturnally averaged NO3 columns between 5–7×1013 molec cm−2 during October through March, and 5–22×1013 molec cm−2 during April through September. A subset of the data, with diurnal variability vastly different from the temporal profile obtained from one-dimensional stratospheric model calculations, clearly has boundary layer contributions; this was confirmed by simultaneous long-path DOAS measurements. However, even the NO3 columns that did follow the modeled time evolution were often much larger than modeled stratospheric partial columns constrained by realistic temperatures and ozone concentrations. This discrepancy is attributed to substantial tropospheric NO3 in the free troposphere, which may have the same time dependence as stratospheric NO3.

scholarly journals First-principles modeling of X-ray absorption spectra enlightens the processes of scandium sequestration by iron oxides

2020 ◽  
Vol 105 (7) ◽  
pp. 1099-1103 ◽  
Author(s):  
Mathieu Chassé ◽  
Marc Blanchard ◽  
Delphine Cabaret ◽  
Amélie Juhin ◽  
Delphine Vantelon ◽  
...  
Keyword(s):  
Trace Metals ◽  
Iron Oxides ◽  
Absorption Spectra ◽  
First Principles ◽  
Molecular Mechanisms ◽  
Hydration Shell ◽  
Spectral Features ◽  
Edge Structure ◽  
X Ray ◽  
X Ray Absorption

Abstract Scandium is often associated with iron oxides in the environment. Despite the use of scandium as a geochemical tracer and the existence of world-class supergene deposits, uncertainties on speciation obscure the processes governing its sequestration and concentration. Here, we use first-principles approaches to interpret experimental K-edge X-ray absorption near-edge structure spectra of scandium either incorporated in or adsorbed on goethite and hematite, at concentrations relevant for the environment. This modeling helps to interpret the characteristic spectral features, providing key information to determine scandium speciation when associated with iron oxides. We show that scandium is substituted into iron oxides at low concentrations without modifying the crystal structure. When scandium is adsorbed onto iron oxide surfaces, the process occurs through outer-sphere complexation with a reduction in the coordination number of the hydration shell. Considering available X-ray absorption spectra from laterites, the present results confirm that scandium adsorption onto iron oxides is the dominant mechanism of sequestration in these geochemical conditions. This speciation explains efficient scandium recovery through mild metal-lurgical treatments of supergene lateritic ores. The specificities of scandium sorption mechanisms are related to the preservation of adsorbed scandium in million-years old laterites. These results demonstrate the emerging ability to precisely model fine X-ray absorption spectral features of trace metals associated with mineral phases relevant to the environment. It opens new perspectives to accurately determine trace metals speciation from high-resolution spatially resolved X-ray absorption near-edge structure spectroscopy in order to constrain the molecular mechanisms controlling their dynamics.

scholarly journals Relationships between spectral features, iron oxides and colours of surface soils in northern Jordan

2020 ◽  
Vol 72 (1) ◽  
pp. 80-97
Author(s):  
Wahib Sahwan ◽  
Bernhard Lucke ◽  
Tobias Sprafke ◽  
Kim A. Vanselow ◽  
Rupert Bäumler
Keyword(s):  
Iron Oxides ◽  
Spectral Features ◽  
Surface Soils ◽  
Northern Jordan

An Infrared Study of Metal Isopropoxide Precursors for SrTiO3

1984 ◽  
Vol 32 ◽  
Author(s):  
R. E. Riman ◽  
D. M. Haaland ◽  
C.J.M. Northrup ◽  
H. K. Bowen ◽  
A. Bleier
Keyword(s):  
Ir Spectra ◽  
Detailed Analysis ◽  
Infrared Spectra ◽  
Spectral Features ◽  
Absorption Bands ◽  
Infrared Study ◽  
Characteristic Absorption ◽  
Local Environments ◽  
Insight Into ◽  
Hydrolysis Reactions

ABSTRACTA Sr/Ti bimetallic isopropoxide complex was synthesized by two methods. The complex served as a precursor to the production of homogeneous SrTiO3 powders via alkoxide hydrolysis. Infrared spectra were obtained for Sr(OPri)2, Ti(OPri)4, and the product of the syntheses. In addition, the IR spectra of the solutions of each of the alkoxides were followed as hydrolysis reactions proceeded. Detailed analysis of the spectral features support the existence of a 1:1 Sr/Ti bimetallic alkoxide. The new Sr/Ti compound exhibits characteristic absorption bands at (1017, 993, 972, 961 cm−1), (844, 838, 827 cm−1) and (620, 596, and 572 −1). A band at 819−1 might also be associated with the new Sr/Ti bimetallic alkoxide. The infrared spectra suggest that the isopropoxide ligands in the bimetallic alkoxide are in at least three separate local environments. This information offers insight into possible structures for the complex.

scholarly journals Diurnal variation of midlatitudinal NO<sub>3</sub> column abundance over table mountain facility, California

2011 ◽  
Vol 11 (3) ◽  
pp. 963-978 ◽  
Author(s):  
C. M. Chen ◽  
R. P. Cageao ◽  
L. Lawrence ◽  
J. Stutz ◽  
R. J. Salawitch ◽  
...  
Keyword(s):  
Full Moon ◽  
Optical Absorption Spectroscopy ◽  
Spectral Features ◽  
Free Troposphere ◽  
Absorption Bands ◽  
Model Calculations ◽  
Diurnal Variability ◽  
One Dimensional ◽  
Lunar Occultation ◽  
Table Mountain

Abstract. The column abundance of NO3 was measured over Table Mountain Facility, CA (34.4° N, 117.7° W) from May 2003 through September 2004, using lunar occultation near full moon with a grating spectrometer. The NO3 column retrieval was performed with the differential optical absorption spectroscopy (DOAS) technique using both the 623 and 662 nm NO3 absorption bands. Other spectral features such as Fraunhofer lines and absorption from water vapor and oxygen were removed using solar spectra obtained at different airmass factors. We observed a seasonal variation, with nocturnally averaged NO3 columns between 5−7 × 1013 molec cm−2 during October through March, and 5−22 × 1013 molec cm−2 during April through September. A subset of the data, with diurnal variability vastly different from the temporal profile obtained from one-dimensional stratospheric model calculations, clearly has boundary layer contributions; this was confirmed by simultaneous long-path DOAS measurements. However, even the NO3 columns that did follow the modeled time evolution were often much larger than modeled stratospheric partial columns constrained by realistic temperatures and ozone concentrations. This discrepancy is attributed to substantial tropospheric NO3 in the free troposphere, which may have the same time dependence as stratospheric NO3.

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