The variation of Venus cloud investigated from SOIR onboard Venus Express

Mapping Intimacies ◽

10.5194/epsc2020-737 ◽

2020 ◽

Author(s):

Seiko Takagi

Keyword(s):

Near Infrared ◽

Cloud Model ◽

Infrared Region ◽

High Spectral Resolution ◽

Atmospheric Transmission ◽

Infrared Wavelength ◽

Radiative Transfer Calculation ◽

Observation Plan ◽

Venus Express ◽

Spectral Imager

The Venus cloud consists of a main cloud deck at 47 &#8211; 70 km, with thinner hazes above and below. The upper haze on Venus lies above the main cloud surrounding the planet, ranging from the cloud top (70 km) up to as high as 90 km. The Solar Occultation in the InfraRed (SOIR) instrument onboard Venus Express (ESA) was designed to measure the Venusian atmospheric transmission at high altitudes (65 &#8211; 220 km) in the infrared wavelength range (2.2 &#8211; 4.3 &#181;m) with a high spectral resolution. In Takagi et al. (2019), the optical properties of Venus&#8217;s haze layer above 90 km have been investigated using SOIR observations. Vertical and latitudinal profiles of the extinction coefficient, optical thickness, and mixing ratio of aerosols are retrieved. A new cloud model was constructed based on the results of Takagi et al. (2019). In this presentation, I will show the results of a radiative transfer calculation (in the near-infrared region) that incorporates a new cloud model and discuss themeteorological some changes that contribute to cloud variation. Furthermore, I will introduce Venus observation plan using the 1.6 m Pirka telescope and Multi-Spectral Imager (MSI) [Watanabe et al., 2012] mounted on the Cassegrain focus of the telescope at the Nayoro Observatory of Hokkaido University.

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Compact meta-spectral image sensor for mobile applications

Nanophotonics ◽

10.1515/nanoph-2021-0706 ◽

2022 ◽

Vol 0 (0) ◽

Author(s):

Jaesoong Lee ◽

Yeonsang Park ◽

Hyochul Kim ◽

Young-Zoon Yoon ◽

Woong Ko ◽

...

Keyword(s):

Spectral Resolution ◽

Near Infrared ◽

High Efficiency ◽

Infrared Region ◽

Image Sensor ◽

High Spectral Resolution ◽

Infrared Range ◽

Spectral Image ◽

Multilayer Filters ◽

Spectral Imager

Abstract We have demonstrated a compact and efficient metasurface-based spectral imager for use in the near-infrared range. The spectral imager was created by fabricating dielectric multilayer filters directly on top of the CMOS image sensor. The transmission wavelength for each spectral channel was selected by embedding a Si nanopost array of appropriate dimensions within the multilayers on the corresponding pixels, and this greatly simplified the fabrication process by avoiding the variation of the multilayer-film thicknesses. The meta-spectral imager shows high efficiency and excellent spectral resolution up to 2.0 nm in the near-infrared region. Using the spectral imager, we were able to measure the broad spectra of LED emission and obtain hyperspectral images from wavelength-mixed images. This approach provides ease of fabrication, miniaturization, low crosstalk, high spectral resolution, and high transmission. Our findings can potentially be used in integrating a compact spectral imager in smartphones for diverse applications.

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An uppermost haze layer above 100 km found over Venus by the SOIR instrument onboard Venus Express

10.5194/egusphere-egu2020-21185 ◽

2020 ◽

Author(s):

Seiko Takagi ◽

Arnaud Mahieux ◽

Valérie Wilquet ◽

Séverine Robert ◽

Ann Carine Vandaele ◽

...

Keyword(s):

Optical Properties ◽

Optical Thickness ◽

High Spectral Resolution ◽

Infrared Range ◽

Mixing Ratio ◽

High Altitudes ◽

Atmospheric Transmission ◽

Low Latitude ◽

Solar Occultation ◽

Venus Express

The Venus cloud consists of a main cloud deck at 47 &#8211; 70 km, with thinner hazes above and below.The upper haze on Venus lies above the main cloud surrounding the planet, ranging from the top of the cloud (70 km) up to as high as 90 km.The Solar Occultation in the InfraRed (SOIR) instrument onboard Venus Express was designed to measure the Venusian atmospheric transmission at high altitudes (65 &#8211; 220 km) in the infrared range (2.2 &#8211; 4.3 &#181;m) with a high spectral resolution. We investigate the optical properties of Venus&#8217;s haze layer above 90 km using SOIR solar occultation observations. Vertical and latitudinal profiles of the extinction coefficient, optical thickness, and mixing ratio of aerosols are retrieved. One of the most remarkable results is that the aerosol mixing ratio tends to increase with altitude above 90 km at both high and low latitude. We speculate how aerosols could be produced at such high altitudes.

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An uppermost haze layer above 100 km found over Venus by the SOIR instrument onboard Venus Express

Earth Planets and Space ◽

10.1186/s40623-019-1103-x ◽

2019 ◽

Vol 71 (1) ◽

Author(s):

Seiko Takagi ◽

Arnaud Mahieux ◽

Valérie Wilquet ◽

Séverine Robert ◽

Ann Carine Vandaele ◽

...

Keyword(s):

Optical Properties ◽

Optical Thickness ◽

High Spectral Resolution ◽

Infrared Range ◽

Mixing Ratio ◽

High Altitudes ◽

Atmospheric Transmission ◽

Solar Occultation ◽

Low Latitudes ◽

Venus Express

AbstractThe Solar Occultation in the InfraRed (SOIR) instrument onboard Venus Express was designed to measure the Venusian atmospheric transmission at high altitudes (65–220 km) in the infrared range (2.2–4.3 μm) with a high spectral resolution. In this work, we investigate the optical properties of Venus’s haze layer above 90 km using SOIR solar occultation observations. Vertical and latitudinal profiles of the extinction coefficient, optical thickness, and mixing ratio of aerosols are retrieved. One of the most remarkable results is that the aerosol mixing ratio tends to increase with altitude above 90 km at both high and low latitudes. We speculate how aerosols could be produced at such high altitudes.

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Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa058 ◽

2020 ◽

Vol 492 (4) ◽

pp. 5470-5507

Author(s):

E Marfil ◽

H M Tabernero ◽

D Montes ◽

J A Caballero ◽

M G Soto ◽

...

Keyword(s):

High Resolution ◽

Near Infrared ◽

Signal To Noise Ratio ◽

Wavelength Region ◽

Infrared Region ◽

High Signal ◽

Atmospheric Parameters ◽

Infrared Wavelength ◽

The Impact ◽

Higher Sensitivity

ABSTRACT With the purpose of assessing classic spectroscopic methods on high-resolution and high signal-to-noise ratio spectra in the near-infrared wavelength region, we selected a sample of 65 F-, G-, and K-type stars observed with CARMENES, the new, ultra-stable, double-channel spectrograph at the 3.5 m Calar Alto telescope. We computed their stellar atmospheric parameters (Teff, log g, ξ, and [Fe/H]) by means of the stepar code, a python implementation of the equivalent width method that employs the 2017 version of the moog code and a grid of MARCS model atmospheres. We compiled four Fe i and Fe ii line lists suited to metal-rich dwarfs, metal-poor dwarfs, metal-rich giants, and metal-poor giants that cover the wavelength range from 5300 to 17 100 Å, thus substantially increasing the number of identified Fe i and Fe ii lines up to 653 and 23, respectively. We examined the impact of the near-infrared Fe i and Fe ii lines upon our parameter determinations after an exhaustive literature search, placing special emphasis on the 14 Gaia benchmark stars contained in our sample. Even though our parameter determinations remain in good agreement with the literature values, the increase in the number of Fe i and Fe ii lines when the near-infrared region is taken into account reveals a deeper Teff scale that might stem from a higher sensitivity of the near-infrared lines to Teff.

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Characterization and Separation of Traditional and Bio-Plastics by Hyperspectral Devices

Applied Sciences ◽

10.3390/app10082800 ◽

2020 ◽

Vol 10 (8) ◽

pp. 2800

Author(s):

Monica Moroni ◽

Alessandro Mei

Keyword(s):

Near Infrared ◽

New Technologies ◽

Raw Materials ◽

Plastic Material ◽

Infrared Region ◽

Industrial Applications ◽

Hyperspectral Data ◽

Data Detection ◽

Mechanical Recycling ◽

Infrared Wavelength

Nowadays, bio-plastics can contaminate conventional plastics sent to recycling. Furthermore, the low volume of bio-plastics currently in use has discourage the development of new technologies for their identification and separation. Technologies based on hyperspectral data detection may be profitably employed to separate the bio-plastics from traditional ones and to increase the quality of recycled products. In fact, sensing devices make it possible to accomplish the essential requirement of a mechanical recycling technology, i.e., end products which comply with specific standards determined by industrial applications. This paper presents the results of the hyperspectral analysis conducted on two different plastic polymers (PolyEthylene Terephthalate and PolyStyrene) and one bio-based and biodegradable plastic material (PolyLactic Acid) in different phases of their life cycle (primary raw materials and urban waste). The reflectance analysis is focused on the near-infrared region (900–1700 nm) and data are detected with a linear-spectrometer apparatus and a spectroradiometer. A rapid and reliable identification of three investigated polymers is achieved by using simple two near-infrared wavelength operators employing key wavelengths.

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A New Bi-substituted Rare-earth Iron Garnet for a Wideband and Temperature-stabilized Optical Isolator

Journal of Materials Research ◽

10.1557/jmr.2000.0240 ◽

2000 ◽

Vol 15 (8) ◽

pp. 1665-1668 ◽

Cited By ~ 13

Author(s):

Min Huang ◽

Sho Zhang

Keyword(s):

Faraday Rotation ◽

Near Infrared ◽

Wavelength Region ◽

Infrared Region ◽

Faraday Rotator ◽

Absorption Loss ◽

Infrared Wavelength ◽

Optical Isolator ◽

Near Infrared Region ◽

Iron Garnet

A wideband and temperature-stabilized optical isolator for 1.55-μm wavelength was developed using a new Bi-substituted holmium–ytterbium ion garnet (HoYbBiIG) single crystal as a Faraday rotator. The optical isolator features 0.34-μm bandwidth, less 0.6 dB insertion loss and over 37 dB backward loss at a wavelength of (1.55 ± 0.17) μm throughout the temperature range from −10 to 60 °C. The Faraday rotation and optical absorption loss of HoYbBiIG were investigated in the near-infrared wavelength region (λ = 0.9 to 1.7 μm). The specific Faraday rotation of Ho0.85Yb1.02Bi1.13Fe5O12 is about −767°/cm at λ = 1.55 μm. The Faraday rotation wavelength and temperature characteristics of HoYbBiIG crystals are also discussed. These results indicate that the Bi-substituted holmium–ytterbium iron garnet single crystals realize a high Faraday rotation stability against temperature and wavelength in the near-infrared region.

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Discriminating between hazy and clear hot-Jupiter atmospheres with CARMENES

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038629 ◽

2020 ◽

Vol 643 ◽

pp. A24

Author(s):

A. Sánchez-López ◽

M. López-Puertas ◽

I. A. G. Snellen ◽

E. Nagel ◽

F. F. Bauer ◽

...

Keyword(s):

High Altitude ◽

Water Vapour ◽

Rayleigh Scattering ◽

Near Infrared ◽

Relative Strength ◽

High Spectral Resolution ◽

Absorption Bands ◽

Infrared Wavelength ◽

Hot Jupiters ◽

Water Vapour Absorption

Context. Relatively large radii of some hot Jupiters observed in the ultraviolet and blue-optical are generally interpreted to be due to Rayleigh scattering by high-altitude haze particles. However, the haze composition and its production mechanisms are not fully understood, and observational information is still limited. Aims. We aim to study the presence of hazes in the atmospheres of HD 209458 b and HD 189733 b with high spectral resolution spectra by analysing the strength of water vapour cross-correlation signals across the red optical and near-infrared wavelength ranges. Methods. A total of seven transits of the two planets were observed with the CARMENES spectrograph at the 3.5 m Calar Alto telescope. Their Doppler-shifted signals were disentangled from the telluric and stellar contributions using the detrending algorithm SYSREM. The residual spectra were subsequently cross-correlated with water vapour templates at 0.70–0.96 μm to measure the strength of the water vapour absorption bands. Results. The optical water vapour bands were detected at 5.2σ in HD 209458 b in one transit, whereas no evidence of them was found in four transits of HD 189733 b. Therefore, the relative strength of the optical water bands compared to those in the near-infrared were found to be larger in HD 209458 b than in HD 189733 b. Conclusions. We interpret the non-detection of optical water bands in the transmission spectra of HD 189733 b, compared to the detection in HD 209458 b, to be due to the presence of high-altitude hazes in the former planet, which are largely absent in the latter. This is consistent with previous measurements with the Hubble Space Telescope. We show that currently available CARMENES observations of hot Jupiters can be used to investigate the presence of haze extinction in their atmospheres.

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