Shadow-aware terrain correction for karst landforms using remote sensing data

The design of solar concentrating collectors for the effective utilization of solar energy is a challenging condition due to tracking errors leading to different divergences of the solar incidence angle. To enhance the optical performance of solar parabolic trough collectors (SPTC) under a diverged solar incidence angle, an additional compound parabolic concentrator (CPC) is introduced as a secondary reflector. SPTC with CPC is designed and modeled for a single axis-tracking concentrating collector based on the local ambient conditions. In this work, the optical performance of the novel SPTC system with and without a secondary reflector is investigated using MATLAB and TRACEPRO software simulations for various tracking errors. The significance parameters such as the solar incidence angle, aperture length, receiver tube diameter, rim angle, concentration ratio, solar radiation, and absorbed flux are analyzed. The simulation results show that the rate of the absorbed flux on the receiver tube is significantly improved by providing the secondary reflector, which enhances the optical efficiency of the collector. It is found that the optical efficiency of the SPTC with a secondary reflector is 20% higher than the conventional collector system for a solar incidence angle of 2°. This work can effectively direct the choice of optimal secondary reflectors for SPTC under different design and operating conditions.

We examine Saturn’s nonauroral (dayglow) emissions at Lyα observed by the Cassini/Ultraviolet Imaging Spectrograph (UVIS) instrument from 2003 until 2017, to constrain meridional and seasonal trends in the upper atmosphere. We separate viewing geometry effects from trends driven by atmospheric properties, by applying a multivariate regression to the observed emissions. The Lyα dayglow brightnesses depend on the incident solar flux, solar incidence angle, emission angle, and observed latitude. The emissions across latitudes and seasons show a strong dependence with solar incidence angle, typical of resonantly scattered solar flux and consistent with no internal source such as electroglow. We observe a bulge in Lyα brightnesses that shifts with the summer season from the southern to the northern hemisphere. We estimate atomic hydrogen optical depths above the methane homopause level for dayside disk observations (2004–2016) by comparing observed Lyα emissions to a radiative transfer model. We model emissions from resonantly scattered solar flux and a smaller but significant contribution by scattered photons from the interplanetary hydrogen (IPH) background. During the northern summer, inferred hydrogen optical depths steeply decrease with latitude toward the winter hemisphere from a northern hemisphere bulge, as predicted by a 2D seasonal photochemical model. The southern hemisphere mirrors this trend during its summer. However, inferred optical depths show substantially more temporal variation between 2004 and 2016 than predicted by the photochemical model. We benchmark our brightness values by comparing observed IPH Lyα emissions from Cassini/UVIS in 2006 with a model of the IPH emissions. Cassini/UVIS observations agree well with the modeled IPH background.

The focus of this presentation is the three-dimensional visualization of Mars dust storms from spacecraft images. The dust storm height is determined by their shadows. Image parameters such as the solar incidence angle, solar azimuth angle, latitude, and longitude are taken into account. Interactive three-dimensional maps of dust storms are created. This presentation includes satellite images from MARCI/MRO (Mars Color Imager/Mars Reconnaissance Orbiter) in the years 2020-2021. This adds to a better understanding of Mars dust storms. This works uses the MeteoMARS tool [1], the NASA PDS Imaging Node [2], the NASA Integrated Software for Imagers and Spectrometers, and the QGIS software [3].[1] http://meteomars.pamplonetario.org/[2] https://pds-imaging.jpl.nasa.gov/[3] https://www.qgis.org/en/site/

tc-cylinder: An optimized algorithm for accurate topography effect from high-resolution digital elevation models

SummaryAccurate terrain corrections are important for all gravity surveying. In airborne surveys, a digital model of the terrain is constructed and terrain corrections are calculated at each airborne measurement point. Airborne gravity gradiometry is of high spatial resolution and is particularly sensitive to nearby topographic variations, placing particular requirements on the terrain corrections. A combination of mathematical analysis and simulation studies has led to quantification of the requirements: current on-shore, low-level gradiometer surveys require sub-metre accuracy in navigation and in digital terrain model heights; cell sizes (and therefore also topographic sampling) in the terrain model should be about one-third of the ground clearance. The choice of terrain correction density depends on the application and it is important that the interpreter of the corrected gravity data has the ability to test the impact of changes in this density.Accurate calculation of the gravity gradient field at the airborne sampling points may be achieved by a wide variety of either spatial or harmonic domain methods. Calculation in the harmonic domain is fast but assumes the data represent a periodic function on a planar surface. Padding methods for periodic extension and piecewise continuation away from a plane both add error and slow the calculation. Spatial domain methods are slower but can be sped up by the use of various approximations. In both cases, a clear understanding of accuracy requirements is essential for making an appropriate tradeoff between accuracy and speed.

Expressions for thermal deflections of uniform thin beams and plates exposed to solar heating are obtained as a function of the properties of the material and the solar incidence angle. The major effect of the solar radiation pressure interacting with the thermally deformed structure is found to give rise to disturbance moments on the structure. The thermal deformations of the structures are assumed to be within 0.1 percent of the characteristic length of the structure. With the assumed thermal deformations, the resulting uncontrolled transient responses of these geosynchronous orbiting structures to the solar radiation pressure induced disturbances are simulated. The resulting rigid modal oscillations are found to be an order of magnitude larger than for those cases previously considered in which only the solar radiation pressure effect on vibrating structures was treated. Modifications of control laws and/or the feedback gain values are considered in order to improve the transient response characteristics under the thermally induced disturbances.

A new PV module performance model based on separation of diffuse and direct light

This study presents a new optimized broadband optical short wave pass (OSWP) edge filter designed for smart window applications to increase energy efficiency. The proposed filter has a dielectric structure with double layer composed of alternative high and low refractive index materials, which is designed to transmit the visible light and reflect the near-infrared (NIR) radiation. To achieve this functionality, we used the transfer matrix method (TMM) with the needle synthesis technique through the Essential Macleod software, which allows the accurate optimization of the thickness of the layer for maximum spectral control. The simulation results show that the filter maintains high visible light transmittance (>96%), while effectively blocks infrared wavelengths (750–1500 nm), with different performance as a function of the angle of incidence. The passive modulation properties of the filter provide seasonally adaptive thermal regulation, making it a viable solution for energy-saving smart window technologies. The results are relevant with the real world’s solar incident angles in Riyadh, Saudi Arabia.

Optical evaluation of a smart transparent insulation material for window application

An air-based corrugated cavity-receiver for solar parabolic trough concentrators

Intercropping, growing at least two different crop species simultaneously in the same field, is a significant cropping system for global food security with more practice and attention recent years. The most remarkable advantage of intercropping is producing a higher yield or income due to more efficient use of agricultural sources. Specifically, the intercropping system utilizes nutrient and water more efficiently underground and intercepts more radiation aboveground. However, modeling intercropping system by crop model is still difficult and has two dominant challenges. One challenge is to quantify the competition of underground source between intercropped species, and the other one is to determine the radiation partitioning by intercropped species. With the view factor theory applied in radiation transmission, several models were established to simulate the light competition of strip intercropping, but most of the models ignore solar incident angles variation during one day and assume the indirect light traverse a whole hedgerow of the taller canopy. Although many models make great attempt on partitioning the indirect light, the extinction coefficient is not matched with the beer’s law. In our study, the radiation transmission model is based on geometrical relationships of crop height, calculating a beam transmission by spatial and temporal integration. Specifically, the same with direct light, the extinction coefficient of an indirect beam is established a numerical functional relation with the solar incident angle which is defined by crop heights and row widths of intercropped species. Furthermore, Gauss-Legendre integral formula are used to solve the indefinite integral caused by angular relationship during the temporal integration. The optimal number of nodes in Gauss-Legendre integral formula is five in our study and the error is generally less than 1%. Compared with existed models, the radiation interception model in our study is more stable and precise especially when the heights of crops are close or greatly discrepant. Further study including border row effect theory and heterogeneous canopy theory is also able to applied in our model.

It is the purpose of this paper to demonstrate how the matrix operator method can be effectively implemented to couple the radiation fields of the atmosphere and ocean. Azimuthally averaged radiances and irradiances are presented as a function of optical depth for a conservative Rayleigh scattering medium of total optical thickness τmax = 1000 with a dielectric interface placed at optical depths of 0.01, 0.1, 1.0, and 10.0, and for various solar incident angles.

Single basin double slope solar still with minimum basin depth and energy storing materials

To provide a theoretical basis for identification and detection of oil spill pollution on the sea surface, based on the polarization reflection coefficient of Fresnel reflection formula and combined with polarization bidirectional reflectivity factor and probability density distribution function of rough sea surface, a perfect pBRDF model was established. Then the polarization reflection distribution function of sea water and oil film was simulated under different solar incident angles, different detector observation angles and different sea surface wind speed and wind directions. The results show that, firstly, P-polarization reflectance reaches 1.0×10−5 and 2.5×10−5 respectively when the solar zenith angle of seawater and oil film is 53° and 56°. S-polarized reflectance increases with the increase of the solar zenith angle. Moreover, the higher sea surface wind speed is, the smaller peak value of polarization reflectance is. Additionally, wind direction only changes spatial position of pBRDF. Finally, the spatial distribution of linear polarization degree between seawater and oil film is obviously different. Experiment platform was set up with the camera working at 40°. The conclusion is obtained that the linear polarization of seawater and oil film is between 0.2−0.4 and 0.5−0.7, respectively. It also shows that using polarization detection to obtain the polarization degree and polarization angle of the target scene can improve the image quality.

Using luminescence to date the burial and exposure ages of rock surfaces has been a revolutionary new geochronological approach developed and refined over the past decade. Rock surface exposure dating is based on the principle that the depth to which the luminescence signal is bleached into a rock surface is dependent on the duration of that rock surface's exposure to sunlight. However, given the recentness of method development, the effects of basic light exposure variables such as the orientation of rock surfaces and the incidence angle of incoming light on bleaching depth have not been tested. We designed an experiment in which we controlled the exposure duration (t) and orientation of granite and sandstone samples while measuring the light attenuation coefficient (μ) and the photon flux at the rock surface (φ0) to determine the influence of spatial orientation of a rock surface on its respective bleaching depth. Our results confirm that the opacity of the rock (μ) and the total insolation have significant effects on the bleaching depth for vertically oriented surfaces. We also observed that the bleaching depth is strongly related to the incidence angle at which the sunlight hits the rock surface, indicating that the effectiveness of bleaching of a given rock surface follows seasonal cycles. Our data suggest that optimal calibration samples for rock surface exposure dating should be of the same lithology and have the same geographical location and orientation of the target sample. Additionally, calibration samples should be collected in year increments so that no season's solar incidence angles are preferred.