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To increase the irradiance generated by an illumination system, multiple sub-systems, each generating their own irradiance distribution can be used. We propose a method using B-spline refinement to find the irradiance distribution that a single sub-system produces, so a desired irradiance distribution is obtained using multiple sub-systems.

We present an approach for measuring the shape of transparent glasses, which enables us to significantly reduce the comparatively long measurement time while increasing the measurement accuracy. Instead of using area-like patterns, we irradiate the object to be measured successively in a locally strongly restricted area with considerably higher irradiance.

The Sun provides nearly all the energy powering the Earth’s climate system, far exceeding all other energy sources combined. The incident radiant energy, the “total solar irradiance,” has been measured by an uninterrupted series of temporally overlapping precision space-borne radiometric instruments since 1978, giving a record spanning more than four 11-year solar cycles. Short-term total-irradiance variations exceeding 0.1% can occur over a few days while variations of ~ 0.1% in-phase with the solar cycle are typical. Knowledge of solar variability on timescales longer than the current multi-decadal space-borne record relies on solar-activity proxies and models, which indicate similar-magnitude changes over centuries. Spectrally resolved space-borne irradiance measurements in the ultraviolet have been acquired continuously since 1979, while measurements contiguously spanning the near-ultraviolet to the near-infrared began in 2003. The combination of long-term total- and spectral-irradiance measurements helps determine both the solar causes of irradiance variability, which are primarily due to solar-surface magnetic-activity regions such as sunspots and faculae, and the mechanisms by which solar variability affects the Earth’s climate system, with global and regional temperatures responding to variability at solar-cycle and longer timescales. To better understand these solar influences, the most modern total-irradiance instruments are approaching the needed climate-driven measurement accuracy and stability requirements for detection of potential long-term solar-variability trends, while the latest spectral-irradiance instruments are beginning to be able to discern solar-cycle variability. Focusing on the space-borne era where such measurements are the most accurate and stable, this article describes solar-irradiance instrument designs, capabilities, and operational methodologies. It summarizes the many total- and spectral-irradiance measurements available and the measured solar variabilities on timescales from minutes to solar cycles and discusses extrapolations via models to longer timescales. Measurement composites and reference spectra are reviewed. Current capabilities and future directions are described along with the climate-driven solar-irradiance measurement requirements.

The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). This 17-year mission made TSI and SSI observations during the declining phase of Solar Cycle 23, during all of Solar Cycle 24, and at the very beginning of Solar Cycle 25. The SORCE solar-variability results include comparisons of the solar irradiance observed during Solar Cycles 23 and 24 and the solar-cycle minima levels in 2008 – 2009 and 2019 – 2020. The differences between these two minima are very small and are not significantly above the estimate of instrument stability over the 11-year period. There are differences in the SSI variability for Solar Cycles 23 and 24, notably for wavelengths longer than 250 nm. Consistency comparisons with SORCE variability on solar-rotation timescales and solar-irradiance model predictions suggest that the SORCE Solar Cycle 24 SSI results might be more accurate than the SORCE Solar Cycle 23 results. The SORCE solar-variability results have been useful for many Sun–climate studies and will continue to serve as a reference for comparisons with future missions studying solar variability.

Existing studies lack experiments on the influence of tilt angle on BPV panel performance under identical ambient environmental conditions, particularly regarding the thermal performance. In this study, an outdoor experimental platform was built to explore the influence of different tilt angles on the thermal-electrical performance of a BPV panel in summer. The results show that the average temperature on the front side of the BPV panel first increases and then decreases as the tilt angle increases, while the average temperature on the rear side and the instantaneous electrical power continuously decrease. When irradiance reaches the maximum value of 903 W/m 2 during the experimental test, the electrical power of the BPV panel with a tilt angle of 12° reaches 403.5 W.

The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). Three important accomplishments of the SORCE mission are i) the continuation of the 42-year-long TSI climate data record, ii) the continuation of the ultraviolet SSI record, and iii) the initiation of the near-ultraviolet, visible, and near-infrared SSI records. All of the SORCE instruments functioned well over the 17-year mission, which far exceeded its five-year prime mission goal. The SORCE spacecraft, having mostly redundant subsystems, was also robust over the mission. The end of the SORCE mission was a planned passivation of the spacecraft following a successful two-year overlap with the NASA Total and Spectral Solar Irradiance Sensor (TSIS) mission, which continues the TSI and SSI climate records. There were a couple of instrument anomalies and a few spacecraft anomalies during SORCE’s long mission, but operational changes and updates to flight software enabled SORCE to remain productive to the end of its mission. The most challenging of the anomalies was the degradation of the battery capacity that began to impact operations in 2009 and was the cause for the largest SORCE data gap (August 2013 – February 2014). An overview of the SORCE mission is provided with a couple of science highlights and a discussion of flight anomalies that impacted the solar observations. Companion articles about the SORCE instruments and their final science data-processing algorithms provide additional details about the instrument measurements over the duration of the mission.

The final version (V.19) of the total solar irradiance data from the SOlar Radiation and Climate Experiment (SORCE) Total Irradiance Monitor has been released. This version includes all calibrations updated to the end of the mission and provides irradiance data from 25 February 2003 through 25 February 2020. These final calibrations are presented along with the resulting final data products. An overview of the on-orbit operations timeline is provided as well as the associated changes in the time-dependent uncertainties. Scientific highlights from the instrument are also presented. These include the establishment of a new, lower TSI value; accuracy improvements to other TSI instruments via a new calibration facility; the lowest on-orbit noise (for high sensitivity to solar variability) of any TSI instrument; the best inherent stability of any on-orbit TSI instrument; a lengthy (17-year) measurement record benefitting from these stable, low-noise measurements; the first reported detection of a solar flare in TSI; and observations of two Venus transits and four Mercury transits.

In the literature several models have been derived by different authors in order to predict the solar irradiance intensity over inclined surfaces, however for the most models accuracy at various inclinations have not been verified. The study evaluated the estimation of solar irradiance at different tilt angles by means of different models based on the experimental measurements. For this purpose, two groups of models (isotropic and anisotropic) were carried out: the first group of models was used for estimating the diffuse solar irradiance component, and the second group was used for estimating the global solar irradiance. Five models have been selected and implemented for the estimation of the diffuse solar irradiance component, and five models have been selected for the estimation of global solar irradiance. The results of the analysis were compared with local experimental measurements for diffuse radiation and global irradiance. There are three tilt angles (0°, 30°, 60°) and a two-axis tracking system has been determent for comparison experiments with the model estimated results. The results showed all the selected models generated an error percentage in both the diffuse and global irradiance investigations.

The Solar Radiation and Climate Experiment (SORCE) was a NASA mission that operated from 2003 to 2020 to provide key climate-monitoring measurements of total solar irradiance (TSI) and solar spectral irradiance (SSI). This topical collection provides an overview of some of the key SORCE science results, an overview of mission operations and how anomalies impacted the science observations, a detailed description of the updated algorithms used in producing the final data products of TSI and SSI from the four SORCE instruments, and results from an underflight calibration-rocket experiment flown in June 2018. The 17-year-long SORCE mission has made many contributions to the climate records of TSI and SSI that date back to the 1970s, and, fortunately, similar observations from the Total and Spectral Solar Irradiance Sensor (TSIS-1) are able to continue these Sun-climate records after SORCE without a gap.

Neutron monitor counting rates and solar wind velocity, interplanetary magnetic field, sunspot number and total solar irradiance measurements from 2013 to 2018 corresponding to the end of solar maximum and the decreasing phase of the Solar Cycle 24 have been used. The main objective is to check whether the periodicities observed in the cosmic rays are affected by the magnetic rigidity or the height at which the neutron monitors are placed. A Global Neutron Monitor (GNM) has been defined as representative of the neutron monitor global network. This GNM is constructed by averaging the counting rates of a set of selected neutron monitors. The selection process is based on the combination of three new data quality criteria, which are applied to neutron monitors in the Neutron Monitor Data Base giving a final pool of 22 selected neutron monitors. Morlet wavelet analysis is applied to the GNM and the selected solar activity parameters to find the common periodicities. Short-term periodicities of 13.5, 27, 48, 92, 132 and 298 days have been observed in cosmic ray intensity. A clear inverse relationship between rigidity and spectral power has been obtained for the 13.5-, 48-, 92-, 132-day periods. A not so clear but still observed direct relationship between the height of the neutron monitors and the spectral power for the 48-, 92-, 132-day periods has been also found. The periodicity of 92 days is the one which shows the highest dependence with rigidity cutoff and height. As far as we know, this is the first time that these dependencies are reported. We think that these observations could be explained by assuming some cosmic ray intensity energy dependence in such periodicities and a competitive effect between rigidity and height.