Topic
Solar constant
About: Solar constant is a research topic. Over the lifetime, 967 publications have been published within this topic receiving 29647 citations.
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01 Jan 1977
2 citations
TL;DR: A group of precision pyrheliometers for use on the ground, in balloons and in spacecraft, has been constructed and a second-generation solar constant monitor, SCM-2, is under construction as mentioned in this paper.
Abstract: A group of precision pyrheliometers, designated PVS-7 and PVS-8, for use on the ground, in balloons and in spacecraft, has been constructed and a second-generation solar constant monitor, SCM-2, is under construction. The SCM-2 incorporates a precision solar pointing and tracking system with a pointing accuracy of 0,2°, a value well below the value of 0,5° which is shown to be the limit for precise pyrheliometry. With this type of equipment, high-altitude balloon SC measurements constitute a useful supplement to satellite measurements by providing an absolute link of sufficient accuracy to permit the evaluation of possible SC trends.
2 citations
TL;DR: In this paper, a thermal balance test under 13 solar constants was performed on the first model of EUI, the Structural and Thermal Model, and the set-up of the test, and correlation with the thermal model performed to deduce the unknown thermal parameters of the instrument and assess its temperature profile under real flight conditions are also presented.
Abstract: Solar Orbiter EUI instrument was submitted to a high solar flux to correlate the thermal model of the instrument. EUI, the Extreme Ultraviolet Imager, is developed by a European consortium led by the Centre Spatial de Liege for the Solar Orbiter ESA M-class mission. The solar flux that it shall have to withstand will be as high as 13 solar constants when the spacecraft reaches its 0.28AU perihelion. It is essential to verify the thermal design of the instrument, especially the heat evacuation property and to assess the thermo-mechanical behavior of the instrument when submitted to high thermal load. Therefore, a thermal balance test under 13 solar constants was performed on the first model of EUI, the Structural and Thermal Model. The optical analyses and experiments performed to characterize accurately the thermal and divergence parameters of the flux are presented; the set-up of the test, and the correlation with the thermal model performed to deduce the unknown thermal parameters of the instrument and assess its temperature profile under real flight conditions are also presented.
2 citations
TL;DR: In this paper, a simple formula to predict the received global solar irradiance q(t), W/m2 for clear days is suggested on pure theoretical basis, which is expressed in terms of the length of the local day time td which is well defined in literatures on meteorological basis.
Abstract: A simple formula to predict the received global solar irradiance q(t), W/m2 for clear days is suggested on pure theoretical basis. It is expressed in terms of the length of the local day time td which is well defined in literatures on meteorological basis. The introduced distribution is also a function of the maximum value of the daily received irradiance qmax. which in turn is expressed in term of the solar constant. This renders the trial to be a closed system. Thus the obtained distribution is not a semi empirical one. Both cases of symmetrical and asymmetrical distributions for q(t) are considered. For its simplicity it can be easily integrated along the length of the day to get the daily totals of solar energy received by unit horizontal area. This is important for practical applications. Comparison between computed according to the present model and published experimental meteorological data in Barcelona (Spain), Hong Kong (China), Jeddah and Makkah (Saudi Arabia) is given as illustrative examples. Better fitting relative to the published trials for the same locations are obtained. The introduced model itself gives good fitting for the intermediate intervals points of the local day time which is the more effective region. The estimated relative error is 12% for Hong Kong, and it is 7% for Barcelona, Jeddah and Makah.
2 citations
TL;DR: In this paper, the variations of universal times difference UT1-TAI and Earth's rotation parameters were studied in the frequency range of 3====== - 8 yr−1 as a function of the solar activity.
Abstract: The variations of universal times difference UT1-TAI and Earth’s rotation
instantaneous pole coordinates (X,Y) are studied in the frequency range of 3
- 8 yr−1 as a function of the solar activity. It is found that power spectrum
concentrations C1 and C2 are common to solar activity indicators and Earth’s
rotation parameters (ERP). The linear correlation between them is also not a
fortuitous one. Accordingly, by the results of this study the hypothesis of
Djurovic and Pâquet (1996; 1999) that the primary cause of 4-6 year
oscillation lies in solar irradiance is confirmed. Between several mechanisms
responsible for the ERP variations as the most probable are considered the
variations of solar irradiance spectral structure (especially large in its UV
range) and variations of intensity of cosmic X-rays reaching the Earth’s
surface.
2 citations