Photometric modelling and VIS-IR albedo maps of Rhea from Cassini-VIMS

2020 ◽  
Vol 499 (1) ◽  
pp. L62-L66
Author(s):  
G Filacchione ◽  
M Ciarniello ◽  
E D’Aversa ◽  
F Capaccioni ◽  
P Cerroni ◽  
...  
Keyword(s):  
Physical Properties ◽  
Spatial Resolution ◽  
Spectral Properties ◽  
Angular Resolution ◽  
Data Sets ◽  
Water Ice ◽  
Depth Maps ◽  
Cylindrical Projection ◽  
Corrected Data ◽  
Band Depth

ABSTRACT Photometric correction based on the Shkuratov method is applied to derive visible and infrared albedo maps of Rhea from disc-resolved Cassini VIMS data. Differently from I/F images, albedo maps offer an optimal disentanglement of composition and physical properties of the surface from illumination-viewing effects and to study spectral variations occurring at hemispherical and local scales. A similar methodology has been already applied to Dione’s and Tethys’s data sets returned by VIMS. Following the same scheme also for Rhea, spectral albedo is derived at 59 wavelengths between 0.35 and 5.047 µm. Equigonal albedo maps are rendered in cylindrical projection with a 0.5$^\circ \, \times$ 0.5° angular resolution in latitude and longitude, corresponding to a maximum spatial resolution of 6.7 km bin−1. Apart from albedo, 0.35–0.55 and 0.55–0.95 µm spectral slopes and the water ice 1.5–2.0 µm band depth maps are computed from photometric-corrected data with the specific scope to investigate the leading-trailing hemisphere colour-albedo dichotomy and to constrain spectral properties above different morphological units including fresh craters (Inktomi) and bright tectonics features (Wakonda-Avaiki Chasmata).

scholarly journals Simulations of disks in binary systems using parallelized SPH to reach extreme spatial resolution

2003 ◽  
Vol 208 ◽  
pp. 427-428
Author(s):  
D. Molteni ◽  
F. Fauci ◽  
G. Gerardi ◽  
M. A. Valenza
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Numerical Simulations ◽  
Spatial Resolution ◽  
Spectral Properties ◽  
Binary Systems ◽  
Compact Star ◽  
Close Binary ◽  
Gas Transfer ◽  
Set Up

Results of 3D numerical simulations of the gas transfer in close binary systems show that it is possible the production of accretion streams having low specific angular momentum in a region close to the accreting star. These streams are mainly placed above the orbital disc. The eventual formation of such bulges and shock heated flows is interesting in the context of advection dominated solutions and for the explanation of spectral properties of the Black Hole candidates in binary systems. We set up a parallelized version of 3D S.P.H. code, using domain decomposion. with increasing spatial resolution around the compact star.

Spectral Properties of α and β L Rhamno-Indigo Molecules and Activities Prediction Through NBO Analysis. A DFT Study

2016 ◽  
Vol 230 (5-7) ◽  
Author(s):  
Khadidja Adjir ◽  
Majda Sekkal-Rahal ◽  
Aurélien Moncomble ◽  
Jean-Paul Cornard
Keyword(s):  
Physical Properties ◽  
Spectral Properties ◽  
Nbo Analysis ◽  
Dft Study ◽  
Spectral Features

AbstractStructural and physical properties such as some spectral features of

scholarly journals The limb-brightened jet of M87 down to the 7 Schwarzschild radii scale

2018 ◽  
Vol 616 ◽  
pp. A188 ◽  
Author(s):  
J.-Y. Kim ◽  
T. P. Krichbaum ◽  
R.-S. Lu ◽  
E. Ros ◽  
U. Bach ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Angular Resolution ◽  
Magnetic Energy ◽  
Large Mass ◽  
High Angular Resolution ◽  
Data Sets ◽  
Jet Formation ◽  
Physical Conditions ◽  
Self Similar ◽  
Jet Structure

Messier 87 (M 87) is one of the nearest radio galaxies with a prominent jet extending from sub-pc to kpc scales. Because of its proximity and the large mass of its central black hole (BH), it is one of the best radio sources for the study of jet formation. We study the physical conditions near the jet base at projected separations from the BH of ~7–100 Schwarzschild radii (Rsch). Global mm-VLBI Array (GMVA) observations at 86 GHz (λ = 3.5 mm) provide an angular resolution of ~50 μas, which corresponds to a spatial resolution of only 7 Rsch and reach the small spatial scale. We use five GMVA data sets of M 87 obtained from 2004 to 2015 and present new high angular resolution VLBI maps at 86 GHz. In particular, we focus on the analysis of the brightness temperature, the jet ridge lines, and the ratio of jet to counter-jet. The imaging reveals a parabolically expanding limb-brightened jet which emanates from a resolved VLBI core of ~(8–13) Rsch in size. The observed brightness temperature of the core at any epoch is ~(1–3) × 1010 K, which is below the equipartition brightness temperature and suggests magnetic energy dominance at the jet base. We estimate the diameter of the jet at its base to be ~5 Rsch assuming a self-similar jet structure. This suggests that the sheath of the jet may be anchored in the very inner portion of the accretion disk. The image stacking reveals faint emission at the center of the edge-brightened jet on sub-pc scales. We discuss its physical implication within the context of the spine-sheath structure of the jet.

scholarly journals Land cover change analysis in Mexico using 30m Landsat and 250m MODIS data

2015 ◽  
Vol XL-7/W3 ◽  
pp. 367-374 ◽  
Author(s):  
R. R. Colditz ◽  
R. M. Llamas ◽  
R. A. Ressl
Keyword(s):  
Remote Sensing ◽  
Change Detection ◽  
Spatial Resolution ◽  
Spatial Scales ◽  
Time Interval ◽  
Data Sets ◽  
Change Analysis ◽  
Dimensional Error ◽  
Analysis Technique ◽  
Coarse Spatial Resolution

Change detection is one of the most important and widely requested applications of terrestrial remote sensing. Despite a wealth of techniques and successful studies, there is still a need for research in remote sensing science. This paper addresses two important issues: the temporal and spatial scales of change maps. Temporal scales relate to the time interval between observations for successful change detection. We compare annual change detection maps accumulated over five years against direct change detection over that period. Spatial scales relate to the spatial resolution of remote sensing products. We compare fractions from 30m Landsat change maps to 250m grid cells that match MODIS change products. Results suggest that change detection at annual scales better detect abrupt changes, in particular those that do not persist over a longer period. The analysis across spatial scales strongly recommends the use of an appropriate analysis technique, such as change fractions from fine spatial resolution data for comparison with coarse spatial resolution maps. Plotting those results in bi-dimensional error space and analyzing various criteria, the “lowest cost”, according to a user defined (here hyperbolic) cost function, was found most useful. In general, we found a poor match between Landsat and MODIS-based change maps which, besides obvious differences in the capabilities to detect change, is likely related to change detection errors in both data sets.

Unravelling the opposing effects of network clustering on electricity system models with high shares of renewables

2021 ◽  
Author(s):  
Martha Frysztacki ◽  
Jonas Hörsch ◽  
Veit Hagenmeyer ◽  
Tom Brown
Keyword(s):  
Spatial Resolution ◽  
Social Acceptance ◽  
Optimal Solution ◽  
Renewable Resource ◽  
Optimal Investment ◽  
Data Sets ◽  
Network Clustering ◽  
High Resolution Data ◽  
Transmission Expansion ◽  
Expansion Model

<p>Energy systems are typically modeled with a low spatial resolution that is based on administrative boundaries such as countries, which eases data collection and reduces computation times. However, a low spatial resolution can lead to sub-optimal investment decisions for renewable generation, transmission expansion or both. Ignoring power grid bottlenecks within regions tends to underestimate system costs, while combining locations with different renewable capacity factors tends to overestimate costs. We investigate these two competing effects in a capacity expansion model for Europe’s future power system that reduces carbon emissions by 95% compared to 1990s levels, taking advantage of newly-available high-resolution data sets and computational advances. We vary the model resolution by changing the number of substations, interpolating between a 37-node model where every country and synchronous zone is modeled with one node respectively, and a 512-node model based on the location of electricity substations. If we focus on the effect of renewable resource resolution and ignore network restrictions, we find that a higher resolution allows the optimal solution to concentrate wind and solar capacity at sites with higher capacity factors and thus reduces system costs by up to 10.5% compared to a low resolution model. This results in a big swing from offshore to onshore wind investment. However, if we introduce grid bottlenecks by raising the network resolution, costs increase by up to 19% as generation has to be sourced more locally where demand is high, typically at sites with worse capacity factors. These effects are most pronounced in scenarios where transmission expansion is limited, for example, by low social acceptance.</p>

scholarly journals Efficient Hogel-Based Hologram Synthesis Method for Holographic Stereogram Printing

2020 ◽  
Vol 10 (22) ◽  
pp. 8088
Author(s):  
Erkhembaatar Dashdavaa ◽  
Anar Khuderchuluun ◽  
Hui-Ying Wu ◽  
Young-Tae Lim ◽  
Chang-Won Shin ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Spatial Resolution ◽  
Angular Resolution ◽  
Synthesis Method ◽  
Three Dimensional ◽  
Lateral Resolution ◽  
Trade Off ◽  
Optical Experiment ◽  
Holographic Stereogram ◽  
3D Scene

With the development of the holographic printer, printing synthetic hologram requires smaller holographic element (hogel) size to improve spatial resolution of the reconstruction. On the contrary, a larger hogel size affords higher angular resolution, but it leads to a lower lateral resolution and there exists a trade-off problem. In this paper, a hologram synthesis method based on three-dimensional (3D) rendering of computer-generated holographic stereogram (HS) is proposed to limit the spatial-angular trade-off problem. The perspectives of the 3D scene are captured by re-centering the camera method and transformed into parallax-related images by a proposed pixel re-arrangement algorithm for holographic printing. Unlike the conventional approaches, the proposed algorithm not only improves the angular resolution of the reconstruction while maintaining the hogel size fixed, but also keeps the spatial resolution without degradation. The effectiveness of the proposed method is verified by numerical simulation and an optical experiment.

scholarly journals High-resolution mapping of the NO<sub>2</sub> spatial distribution over Belgian urban areas based on airborne APEX remote sensing

2017 ◽  
Vol 10 (5) ◽  
pp. 1665-1688 ◽  
Author(s):  
Frederik Tack ◽  
Alexis Merlaud ◽  
Marian-Daniel Iordache ◽  
Thomas Danckaert ◽  
Huan Yu ◽  
...  
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Urban Areas ◽  
High Spatial Resolution ◽  
European Space Agency ◽  
Correlation Coefficients ◽  
Time Frame ◽  
Quantitative Information ◽  
Data Sets ◽  
Vertical Column

Abstract. We present retrieval results of tropospheric nitrogen dioxide (NO2) vertical column densities (VCDs), mapped at high spatial resolution over three Belgian cities, based on the DOAS analysis of Airborne Prism EXperiment (APEX) observations. APEX, developed by a Swiss-Belgian consortium on behalf of ESA (European Space Agency), is a pushbroom hyperspectral imager characterised by a high spatial resolution and high spectral performance. APEX data have been acquired under clear-sky conditions over the two largest and most heavily polluted Belgian cities, i.e. Antwerp and Brussels on 15 April and 30 June 2015. Additionally, a number of background sites have been covered for the reference spectra. The APEX instrument was mounted in a Dornier DO-228 aeroplane, operated by Deutsches Zentrum für Luft- und Raumfahrt (DLR). NO2 VCDs were retrieved from spatially aggregated radiance spectra allowing urban plumes to be resolved at the resolution of 60  ×  80 m2. The main sources in the Antwerp area appear to be related to the (petro)chemical industry while traffic-related emissions dominate in Brussels. The NO2 levels observed in Antwerp range between 3 and 35  ×  1015 molec cm−2, with a mean VCD of 17.4 ± 3.7  ×  1015 molec cm−2. In the Brussels area, smaller levels are found, ranging between 1 and 20  ×  1015 molec cm−2 and a mean VCD of 7.7 ± 2.1  ×  1015 molec cm−2. The overall errors on the retrieved NO2 VCDs are on average 21 and 28 % for the Antwerp and Brussels data sets. Low VCD retrievals are mainly limited by noise (1σ slant error), while high retrievals are mainly limited by systematic errors. Compared to coincident car mobile-DOAS measurements taken in Antwerp and Brussels, both data sets are in good agreement with correlation coefficients around 0.85 and slopes close to unity. APEX retrievals tend to be, on average, 12 and 6 % higher for Antwerp and Brussels, respectively. Results demonstrate that the NO2 distribution in an urban environment, and its fine-scale variability, can be mapped accurately with high spatial resolution and in a relatively short time frame, and the contributing emission sources can be resolved. High-resolution quantitative information about the atmospheric NO2 horizontal variability is currently rare, but can be very valuable for (air quality) studies at the urban scale.

scholarly journals Time Series High-Resolution Land Surface Albedo Estimation Based on the Ensemble Kalman Filter Algorithm

2019 ◽  
Vol 11 (7) ◽  
pp. 753 ◽  
Author(s):  
Guodong Zhang ◽  
Hongmin Zhou ◽  
Changjing Wang ◽  
Huazhu Xue ◽  
Jindi Wang ◽  
...  
Keyword(s):  
Time Series ◽  
Kalman Filter ◽  
High Resolution ◽  
Spatial Resolution ◽  
Ensemble Kalman Filter ◽  
Land Surface ◽  
Surface Albedo ◽  
Data Sets ◽  
Broadleaf Forest ◽  
Kalman Filter Algorithm

Continuous, long-term sequence, land surface albedo data have crucial significance for climate simulations and land surface process research. Sensors such as the Moderate-Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer (VIIRS) provide global albedo product data sets with a spatial resolution of 500 m over long time periods. There is demand for new high-resolution albedo data for regional applications. High-resolution observations are often unavailable due to cloud contamination, which makes it difficult to obtain time series albedo estimations. This paper proposes an “amalgamation albedo“ approach to generate daily land surface shortwave albedo with 30 m spatial resolution using Landsat data and the MODIS Bidirectional Reflectance Distribution Functions (BRDF)/Albedo product MCD43A3 (V006). Historical MODIS land surface albedo products were averaged to obtain an albedo estimation background, which was used to construct the albedo dynamic model . The Thematic Mapper (TM) albedo derived via direct estimation approach was then introduced to generate high spatial-temporal resolution albedo data based on the Ensemble Kalman Filter algorithm (EnKF). Estimation results were compared to field observations for cropland, deciduous broadleaf forest, evergreen needleleaf forest, grassland, and evergreen broadleaf forest domains. The results indicated that for all land cover types, the estimated albedos coincided with ground measurements at a root mean squared error (RMSE) of 0.0085–0.0152. The proposed algorithm was then applied to regional time series albedo estimation; the results indicated that it captured spatial and temporal variation patterns for each site. Taken together, our results suggest that the amalgamation albedo approach is a feasible solution to generate albedo data sets with high spatio-temporal resolution.

Spectral Properties of Water Ice and Contaminants

1985 ◽  
pp. 155-168 ◽  
Author(s):  
Paul G. Lucey ◽  
Roger N. Clark
Keyword(s):  
Spectral Properties ◽  
Water Ice
Sign in / Sign up

Export Citation Format

Share Document