scholarly journals An Efficient and Lightweight Illumination Model for Planetary Bodies Including Direct and Diffuse Radiation

2020 ◽  
Vol 6 (9) ◽  
pp. 84
Author(s):  
Marco Scharringhausen ◽  
Lars Witte
Keyword(s):  
Small Body ◽  
Diffuse Radiation ◽  
Radiation Wavelength ◽  
Main Belt ◽  
Multiple Systems ◽  
Direct Radiation ◽  
Illumination Model ◽  
Digital Terrain ◽  
Simulated Images ◽  
Tracing Method

We present a numerical illumination model to calculate direct as well as diffuse or Hapke scattered radiation scenarios on arbitrary planetary surfaces. This includes small body surfaces such as main belt asteroids as well as e.g., the lunar surface. The model is based on the ray tracing method. This method is not restricted to spherical or ellipsoidal shapes but digital terrain data of arbitrary spatial resolution can be fed into the model. Solar radiation is the source of direct radiation, wavelength-dependent effects (e.g. albedo) can be accounted for. Mutual illumination of individual bodies in implemented (e.g. in binary or multiple systems) as well as self-illumination (e.g. crater floors by crater walls) by diffuse or Hapke radiation. The model is validated by statistical methods. A χ2 test is utilized to compare simulated images with DAWN images acquired during the survey phase at small body 4 Vesta and to successfully prove its validity.

scholarly journals An Efficient and Leightweight Illumination model for Planetary Bodies including Direct and Diffuse Radiation

2019 ◽  
Author(s):  
Marco Scharringhausen ◽  
Lars Witte
Keyword(s):  
Solar Radiation ◽  
Lunar Surface ◽  
Small Body ◽  
Diffuse Radiation ◽  
Radiation Wavelength ◽  
Main Belt ◽  
Multiple Systems ◽  
Direct Radiation ◽  
Illumination Model ◽  
Digital Terrain

We present a numerical illumination model to calculate direct as well as diffuse or Hapke scattered radiation scenarios on arbitrary planetary surfaces. This includes small body surfaces such as main belt asteroids as well as e.g. the lunar surface. The model is based on the raytracing method. This method is not restricted to spherical or ellipsiodal shapes but digital terrain data of arbitrary spatial resolution can be fed into the model. Solar radiation is the source of direct radiation, wavelength-dependent effects (e.g. albedo) can be accounted for. Mutual illumination of individual bodies in implemented (e.g. in binary or multiple systems) as well as self-illumination (e.g. crater floors by crater walls) by diffuse or Hapke radiation. The model is validated by statistical methods. A χ2 test is undertaken to compare simnulated images with DAWN images acquired during the survey phase at small body 4 Vesta.

scholarly journals Impacts of Stratospheric Sulfate Geoengineering on Global Solar Photovoltaic and Concentrating Solar Power Resource

2017 ◽  
Vol 56 (5) ◽  
pp. 1483-1497 ◽  
Author(s):  
Christopher J. Smith ◽  
Julia A. Crook ◽  
Rolf Crook ◽  
Lawrence S. Jackson ◽  
Scott M. Osprey ◽  
...  
Keyword(s):  
Solar Power ◽  
Climate Model ◽  
Diffuse Radiation ◽  
Lower Atmosphere ◽  
Energy Output ◽  
Future Climate Change ◽  
Change Scenario ◽  
Solar Photovoltaic ◽  
Concentrating Solar Power ◽  
Direct Radiation

AbstractIn recent years, the idea of geoengineering, artificially modifying the climate to reduce global temperatures, has received increasing attention because of the lack of progress in reducing global greenhouse gas emissions. Stratospheric sulfate injection (SSI) is a geoengineering method proposed to reduce planetary warming by reflecting a proportion of solar radiation back into space that would otherwise warm the surface and lower atmosphere. The authors analyze results from the Met Office Hadley Centre Global Environment Model, version 2, Carbon Cycle Stratosphere (HadGEM2-CCS) climate model with stratospheric emissions of 10 Tg yr−1 of SO2, designed to offset global temperature rise by around 1°C. A reduction in concentrating solar power output of 5.9% on average over land is shown under SSI relative to a baseline future climate change scenario (RCP4.5) caused by a decrease in direct radiation. Solar photovoltaic energy is generally less affected as it can use diffuse radiation, which increases under SSI, at the expense of direct radiation. The results from HadGEM2-CCS are compared with the Goddard Earth Observing System Chemistry–Climate Model (GEOSCCM) from the Geoengineering Model Intercomparison Project (GeoMIP), with 5 Tg yr−1 emission of SO2. In many regions, the differences predicted in solar energy output between the SSI and RCP4.5 simulations are robust, as the sign of the changes for both HadGEM2-CCS and GEOSCCM agree. Furthermore, the sign of the total and direct annual mean radiation changes evaluated by HadGEM2-CCS agrees with the sign of the multimodel mean changes of an ensemble of GeoMIP models over the majority of the world.

scholarly journals VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis

2021 ◽  
Vol 654 ◽  
pp. A56
Author(s):  
P. Vernazza ◽  
M. Ferrais ◽  
L. Jorda ◽  
J. Hanuš ◽  
B. Carry ◽  
...  
Keyword(s):  
Rotation Period ◽  
High Angular Resolution ◽  
Main Belt ◽  
Volume Estimate ◽  
Multiple Systems ◽  
3D Shape ◽  
Asteroid Exploration ◽  
Reconstruction Methods ◽  
C Complex ◽  
Compositional Diversity

Context. Until recently, the 3D shape, and therefore density (when combining the volume estimate with available mass estimates), and surface topography of the vast majority of the largest (D  ≥ 100 km) main-belt asteroids have remained poorly constrained. The improved capabilities of the SPHERE/ZIMPOL instrument have opened new doors into ground-based asteroid exploration. Aims. To constrain the formation and evolution of a representative sample of large asteroids, we conducted a high-angular-resolution imaging survey of 42 large main-belt asteroids with VLT/SPHERE/ZIMPOL. Our asteroid sample comprises 39 bodies with D  ≥ 100 km and in particular most D  ≥ 200 km main-belt asteroids (20/23). Furthermore, it nicely reflects the compositional diversity present in the main belt as the sampled bodies belong to the following taxonomic classes: A, B, C, Ch/Cgh, E/M/X, K, P/T, S, and V. Methods. The SPHERE/ZIMPOL images were first used to reconstruct the 3D shape of all targets with both the ADAM and MPCD reconstruction methods. We subsequently performed a detailed shape analysis and constrained the density of each target using available mass estimates including our own mass estimates in the case of multiple systems. Results. The analysis of the reconstructed shapes allowed us to identify two families of objects as a function of their diameters, namely “spherical” and “elongated” bodies. A difference in rotation period appears to be the main origin of this bimodality. In addition, all but one object (216 Kleopatra) are located along the Maclaurin sequence with large volatile-rich bodies being the closest to the latter. Our results further reveal that the primaries of most multiple systems possess a rotation period of shorter than 6 h and an elongated shape (c∕a ≤ 0.65). Densities in our sample range from ~1.3 g cm−3 (87 Sylvia) to ~4.3 g cm−3 (22 Kalliope). Furthermore, the density distribution appears to be strongly bimodal with volatile-poor (ρ ≥ 2.7 g cm−3) and volatile-rich (ρ ≤ 2.2 g cm−3) bodies. Finally, our survey along with previous observations provides evidence in support of the possibility that some C-complex bodies could be intrinsically related to IDP-like P- and D-type asteroids, representing different layers of a same body (C: core; P/D: outer shell). We therefore propose that P/ D-types and some C-types may have the same origin in the primordial trans-Neptunian disk.

Small body exploration in China

2020 ◽  
Author(s):  
Jiangchuan Huang ◽  
Xiaojing Zhang ◽  
Tong Wang ◽  
Zhuoxi Huo ◽  
Xian Shi ◽  
...  
Keyword(s):  
Solar System ◽  
Design Research ◽  
Small Body ◽  
Measurement Data ◽  
Main Belt ◽  
Small Bodies ◽  
Asteroid Exploration ◽  
Full Picture ◽  
Exploration Mission ◽  
And Migration

<p align="left"><span>The past twenty years have seen an evolution in the definition and categorization of small bodies in the Solar System. While new types of bodies are being discovered at an increasing pace, objects familiar to us have been rediscovered with traits previously unknown, resulting in “hybrid” bodies like “Main-belt comets” or “active asteroids” [1]. New knowledges of small bodies are essential to further our understanding of the solar system as they directly shed light on planetary formation and evolution scenarios, the distribution and migration of water, and the emergence of life. To get a full picture of these small bodies, it is necessary to carry out detailed and comprehensive investigations, especially with dedicated space missions. As demonstrated by the success of a number of such missions recently completed and ongoing, a growing consensus is emerging that future missions should: 1) cover a diversity of targets, especially those never visited before; 2) characterize the structure and composition of the target body with highest possible resolution. The first Chinese small body mission is designed to take on both challenges by performing sample return from a quasi-satellite of the Earth—2016 HO3 and visiting for the first time a “main-belt comet”--133P/Elst-Pizarro.</span></p> <p align="left"><a name="_GoBack"></a><span>In April 2019, CNSA released an open call of onboard opportunity for an asteroid exploration mission [2]<span lang="zh-CN">，</span>which encourages international cooperation. This asteroid exploration mission is characterized by multi-task, multi-target and multi-mode (e. g. joint exploration by multiple devices, landing and sampling etc.). On the basis of feasibility demonstration, design research and key techniques research, various work of the mission is currently in progress, such as the scientific research of small celestial particles, that is, combining remote sensing and surface in-situ measurement data and features of different scales (sub-millimeter to decimeter) to obtain clues of composition and evolution of small bodies. </span></p> <p align="left"> </p> <p align="left"><span>[1] Hsieh, Henry H., David C. Jewitt, and Yanga R. Fernández. The Astronomical Journal 127(5):2997. (2004).</span></p> <p align="left"><span>[2] http://www.cnsa.gov.cn/n6758823/n6758839/c6805886/part/6780392.pdf </span></p>

scholarly journals How many satellites have been discovered in the Solar System after Galileo?

2010 ◽  
Vol 6 (S269) ◽  
pp. 250-253
Author(s):  
Zhanna Pozhalova ◽  
Dmitrij Lupishko
Keyword(s):  
Solar System ◽  
Kuiper Belt ◽  
Main Belt ◽  
Trojan Asteroids ◽  
Kuiper Belt Objects ◽  
Multiple Systems ◽  
Natural Satellites ◽  
Near Earth Asteroids

AbstractBy the beginning of 2010 the total number of natural satellites and multiple systems in the Solar System was equal to 350, including: 168 satellites of large planets, 119 multiple asteroids (including main-belt and near-Earth asteroids, Mars-crossers and Jupiter Trojan asteroids) and 63 multiple transneptunian and Kuiper-belt objects. Meanwhile, we cannot count precisely how many moons in total have been discovered to date due to the deficiency of accepted definitions.

scholarly journals Annual evolution of global, direct and diffuse radiation and fractions in tilted surfaces

2012 ◽  
Vol 32 (2) ◽  
pp. 247-260
Author(s):  
Adilson P. de Souza ◽  
João F. Escobedo ◽  
Alexandre Dal Pai ◽  
Eduardo N. Gomes
Keyword(s):  
Solar Radiation ◽  
Cloud Cover ◽  
Diffuse Radiation ◽  
Incident Radiation ◽  
Sao Paulo ◽  
Horizontal Surface ◽  
Direct Radiation ◽  
Incident Solar Radiation ◽  
Cover Ratio ◽  
Atmospheric Transmissivity

It was evaluated the annual evolution of global, direct and diffuse components of incident solar radiation on tilted surfaces to 12.85, 22.85 and 32.85º, facing north, in Botucatu, state of São Paulo, Brazil. The radiometric fractions were obtained for each component of the radiation in the aforementioned surfaces, through the ratio with the global and top of the atmosphere radiations. Seasonality was evaluated based on monthly averages of daily values. The measures occurred between 04/1998 and 07/2001 at 22.85º; 08/2001 and 02/2003 at 12.85º; and from 03/2003 to 12/2007 at 32.85º, with concomitant measures in the horizontal surface (reference). The levels of global and direct radiation on tilted surfaces were lower in summer and higher in the equinoxes when compared with the horizontal. The diffuse radiation on tilted surfaces was lower in most months, with losses of up to 65%. A trend of increasing differences occurred between horizontal and tilted surfaces with the increase of the angle in all the components and fractions of incident radiation. The annual evolution of rainfall and cloud cover ratio directly affected the atmospheric transmissivity of direct and diffuse components in the region.

scholarly journals Galileo’s Exploration of Small Bodies

2005 ◽  
Vol 13 ◽  
pp. 722-722
Author(s):  
Torrence Johnson
Keyword(s):  
Small Body ◽  
Ring System ◽  
Space Weathering ◽  
High Porosity ◽  
Main Belt ◽  
Small Bodies ◽  
Weathering Processes ◽  
Final Data ◽  
Small Asteroid

The Galileo mission to the Jupiter system afforded the opportunity to make the first ever flyby observations of main belt asteroids. The first encounter, with 951 Gaspra, revealed an irregular, cratered surface that shows evidence of regolith optical space weathering processes. The second encounter, with 243 Ida, resulted in the discovery of the first confirmed satellite of an asteroid, Dactyl. Measurements of Dactyl’s orbit also allowed a useful determination of mass and density for Ida. In addition to these pioneering asteroid observations, Galileo also made observations of Jupiter’s small inner moons and found that they were the major source for material in Jupiter’s tenuous ring system. During it’s final data taking orbit in 2002, Galileo passed within about 250 km of the irregularly shaped satellite Amalthea. Determination of Amalthea’s mass from tracking data yields a bulk density for this small body of less than 1 gm/cc, suggesting a body of relatively high porosity. This is consistent with the growing body of data on small asteroid densities and estimates of their porosity.

Direct and Diffuse Radiation in the Shallow Cumulus–Vegetation System: Enhanced and Decreased Evapotranspiration Regimes

2017 ◽  
Vol 18 (6) ◽  
pp. 1731-1748 ◽  
Author(s):  
X. Pedruzo-Bagazgoitia ◽  
H. G. Ouwersloot ◽  
M. Sikma ◽  
C. C. van Heerwaarden ◽  
C. M. J. Jacobs ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Land Surface ◽  
Land Surface Model ◽  
Diffuse Radiation ◽  
Surface Fluxes ◽  
Surface Model ◽  
Direct Radiation ◽  
Shallow Cumulus ◽  
Boundary Layer Dynamics

Abstract Guided by a holistic approach, the combined effects of direct and diffuse radiation on the atmospheric boundary layer dynamics over vegetated land are investigated on a daily scale. Three numerical experiments are designed that are aimed at disentangling the role of diffuse and direct radiation below shallow cumulus at the surface and on boundary layer dynamics. A large-eddy simulation (LES) model coupled to a land surface model is used, including a mechanistically immediate response of plants to radiation, temperature, and water vapor deficit changes. The partitioning in direct and diffuse radiation created by clouds and farther inside the canopy is explicitly accounted for. LES results are conditionally averaged as a function of the cloud optical depth. The findings show larger photosynthesis under thin clouds than under clear sky, due to an increase in diffuse radiation and a slight decrease in direct radiation. The reduced canopy resistance is the main driver for the enhanced carbon uptake by vegetation, while the carbon gradient and aerodynamic effects at the surface are secondary. Because of the coupling of CO2 and water vapor exchange through plant stomata, evapotranspiration is also enhanced under thin clouds, albeit to a lesser extent. This effect of diffuse radiation increases the water use efficiency and evaporative fraction under clouds. The dynamic perturbations of the surface fluxes by clouds do not affect general boundary layer or cloud characteristics because of the limited time and space where these perturbations occur. It is concluded that an accurate radiation partitioning calculation is necessary to obtain reliable estimations on local surface processes.

Influence of Sand-Dust on Solar Radiation in the Hinterland of Taklimakan Desert

2020 ◽  
Author(s):  
Lili Jin ◽  
Qing He ◽  
Zhenjie Li ◽  
Ali Mamtimin ◽  
Qilong Miao
Keyword(s):  
Solar Radiation ◽  
Essential Feature ◽  
Meteorological Data ◽  
Global Radiation ◽  
Diffuse Radiation ◽  
Northwest China ◽  
Taklimakan Desert ◽  
Direct Radiation ◽  
Sand Storm ◽  
Sand Dust

<p>In order to reveal the essential feature of radiation in extreme arid region of Northwest China,using the global radiation，direct radiation,diffuse radiation and meteorological data in the Tazhong station( in Takli-makan desert hinterland,83°39'E,38°58'N),the characteristics of atmospheric transparency coefficient,influence of sand-dust on solar radiation were analyzed by the statistical methods.The results show that: The coefficient of atmosphere transparency is better from October to December than other months,but it's worse in spring and summer.The index of the atmosphere transparency P<sub>2</sub> is the most ( least) in clear day ( sand storm day ) .The global radiation is more than 1000 W·m<sup>-</sup><sup>2</sup> in clear day,dust day and sand blowing day,while,it is up to 700 W·m<sup>-</sup><sup>2</sup> in sand storm day at most.The diffuse radiation is partly less than 400 W·m<sup>-</sup><sup>2</sup>,mainly between 100 and 200 W·m<sup>-</sup><sup>2</sup>in clear day.It is less than 600 W·m<sup>-</sup><sup>2</sup> in dusty day mostly. The direct radiation is reduced by dust aerosol.The probability are 41.2%,72.5%,78.1% and 100% when direct radiation is less than 200 W·m<sup>-</sup><sup>2</sup> during clear day,dust day,sand blowing day and sand storm day.The diffuse radiation is gradually concentration high value with the sand of the atmosphere is increased.The variation of every radiation is big in dusty day.The daily curve (value) of diffuse radiation is similar to the global radiation,which is reduced by dust aerosol is the same as the direct radiation.That suggests the atmosphere transparency is closely related to the global radiation,diffuse radiation and direct radiation.</p>

scholarly journals Improvement of Optical Performances Using the Hybrid CPV

2020 ◽  
Vol 7 (2) ◽  
pp. 238-245
Author(s):  
Sarah El Himer ◽  
◽  
Ali Ahaitouf ◽  
Keyword(s):  
Solar Cells ◽  
Silicon Solar Cell ◽  
High Efficiency ◽  
Low Cost ◽  
Diffuse Radiation ◽  
Fresnel Lens ◽  
Silicon Solar Cells ◽  
Optical Efficiency ◽  
Direct Radiation ◽  
Simulation Results

Hybrid Concentrated Photovoltaics (HCPVs) are systems in which additional low-cost silicone solar cells are added to take advantage of the power generated by the diffuse radiation lost when using only multi-junction cells that work only with direct radiation. The work has been tested by simulating the performance of a hybrid CPV system composed of a Fresnel lens associated with a pyramid, multi junction cell as well as additional silicon solar cells. This proposal is compared with an ordinary CPV system and a system based on only silicon solar cells. The simulation results show that the CPV makes it possible to have a high optical efficiency of 94% at the pyramid exit for direct radiation, but this high efficiency rapidly decreases to 0% for diffuse radiation. In this case, the silicon solar cell comes into the scene to converts these diffused or non-concentrated rays into electricity, with an optical efficiency of 85%. It was also found that the Hybrid CPV system was able to increase the power by 21% compared to the CPV system.

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