Showing papers on "Solar constant published in 1995"

Satellite Meteorology: An Introduction

Abstract: Introduction: History of Satellite Meteorology. Scope of The Book. Orbits and Navigation: Newton's Laws. Keplerian Orbits. Orbit Perturbations. Meteorological Satellite Orbits. Satellite Positioning, Tracking and Navigation. Space-Time Sampling. Launch Vehicles and Profiles. Radiative Transfer: Basic Quantities. Blackbody Radiation. The Radiative Transfer Equation. Gaseous Absorption. Scattering. Surface Reflection. Solar Radiation. Meteorological SatelliteInstrumentation: Operational Polar-Orbiting Satellites. Operational Geostationary Satellites. Other Satellite Instruments. Satellite Data Archives. Image Interpretation: Satellite Imagery. Spectral Properties. Image Enhancement Techniques. Geolocation and Calibration. Atmospheric and Surface Phenomena. A Final Note.Temperature and Trace Gases: Sounding Theory. Retrieval Methods. Operational Retrievals. Limb Sounding Retrievals. Ozone and Other Gases. The Split-Window Technique. Winds: Cloud and Vapor Tracking. Winds from Soundings. Ocean Surface Winds. Doppler Wind Measurements. Clouds and Aerosols: Clouds from Sounders. Clouds from Imagers. Clouds from Microwave Radiometry. Stratospheric Aerosols. Tropospheric Aerosols. Precipitation: Visible and Infrared Techniques. Passive Microwave Techniques. Radar. Severe Thunderstorms. Earth Radiation Budget: The Solar Constant. Top of the Atmosphere Radiation Budget. Surface Radiation Budget. The Future: NOAA K, L, M.Mission to Planet Earth. Other Possibilities. A Final Comment. Appendixes: List of Meteorological Satellites. Abbreviations. Principal Symbols. Systeme International Units. Physical Constants. Subject Index.

Long-term total solar irradiance variability during sunspot cycle 22

Abstract: Total solar irradiance measurements from the 1984-1993 Earth Radiation Budget Satellite (ERBS) active cavity radiometer and 1978-1993 Nimbus 7 transfer cavity radiometer spacecraft experiments are analyzed to detect the presence of 11-, 22-, and 80-year irradiance variability components. The analyses confirmed the existence of a significant 11-year irradiance variability component, associated with solar magnetic activity and the sunspot cycle. The analyses also suggest the presence of a 22- or 80-year variability component. The earlier Nimbus 7 and Solar Maximum Mission (SMM) spacecraft irradiance measurements decreased approximately 1.2 and 1.3 W/sq m, respectively, between 1980 and 1986. The Nimbus 7 values increased 1.2 W/sq m between 1986 and 1989. The ERBS irradiance measurements increased 1.3 W/sq m during 1986-1989, and then decreased 0.4 W/sq m (at an annual rate of 0.14 W/sq. m/yr) during 1990-1993. Considering the correlations between ERBS, Nimbus 7, and SMM irradiance trends and solar magnetic activity, the total solar irradiance should decrease to minimum levels by 1997 as solar activity decreases to minimum levels, and then increase to maximum levels by the year 2000 as solar activity rises. The ERBS measurements yielded 165.4 +/- 0.7 W/sq m as the mean irradiance value with measurement accuracies and precisions of 0.2% and 0.02%, respectively. The ERBS mean irradiance value is within 0.2% of the 1367.4, 1365.9, and 1366.9 W/sq m mean values for the SMM, Upper Atmosphere Research Satellite (UARS), and Space Shuttle Atmospheric Laboratory for Applications and Science (ATLAS 1) Solar Constant (SOLCON) active cavity radiometer spacecraft experiments, respectively. The Nimbus 7 measurements yielded 1372.1 W/sq m as the mean value with a measurement accuracy of 0.5%. Empirical irradiance model fits, based upon 10.7 -cm solar radio flux (F10) and photometric sunspot index (PSI), were used to assess the quality of the ERBS, Numbus 7, SMM, and the UARS irradiance data sets and to identify irradiance variability trends which may be caused by drifts or shifts in the spacecraft sensor responses. Comparisons among the fits and measured irradiances indicate that the Nimbus 7 radiometer response shifted by a total of 0.8 W/sq m between September 1989 and April 1990 and that the ERBS and UARS radiometers each drifted approximately 0.5 W/sq m during the first 5 months in orbit.

A slightly more massive young Sun as an explanation for warm temperatures on early Mars.

Abstract: The valley network channels on the heavily cratered ancient surface of Mars suggest the presence of liquid water approx. 3.8 Gyr ago. However, the implied warm climate is difficult to explain in the context of the standard solar model, even allowing for the maximum CO2 greenhouse heating. In this paper we investigate the astronomical and planetary implications of a nonstandard solar model in which the zero-age, main-sequence Sun had a mass of 1.05 +/- 0.02 Solar Mass. The excess mass was subsequently lost in a solar wind during the first 1.2(sup -0.2)(sub +.04) Gyr of the Sun's main sequence phase. The implied mass-loss rate of 4(sup +3)(sub -2) x 10(exp -11) Solar Mass/yr, or about 10(exp 3) times that of the current Sun, may be detectable in several nearby young solar type stars.

X-rays from the Sun

Abstract: X-ray astronomy began in 1948 with the first detection of X-rays from the Sun. Astronomical X-ray observations need to be performed from high-altitude rockets and satellites because the Earth's atmosphere absorbs X-rays. Currently about 100,000 X-ray sources are known all over the sky. The Sun is by far the strongest source. The outermost solar atmosphere, the corona, emits X-rays due to its high temperature of a few million K. Solar X-ray emission is highly variable. Eruptions lead to variations of the X-ray flux on time scales of minutes. The average X-ray flux varies with the 11-year sunspot cycle by a factor of about 1000. Solar X-rays have a profound influence on the Earth's upper atmosphere.

Photosynthesis as a Chloroplast Function

Abstract: The sun is the universal source of energy in the biosphere. During the nuclear-fusion processes occurring in the sun, matter is changed into energy (e.g. 4 protons → helium nucleus + 2 positrons + 4.5 · 10−12 J) which is emitted in the form of electromagnetic radiation (h v) into space. The energy emission of solar radiation corresponds, as a first approximation, to the continuous emission spectrum of a black body at 5800 K. Because of scattering and selective absorption of quanta in the earth’s atmosphere the spectrum of the sun is modified (Fig. 12.1) so that the energy flux is reduced from 1.4 (the solar constant) to ≤0.9 kW · m−2 (sea level). Approximately half this energy is within the 300–800 nm spectral band (“optical window” of the atmosphere; Fig. 12.1) which is in the centre of the photochemically active radiation band (approximately 100–1000 nm).

Development of advanced Si and GaAs solar cells for interplanetary missions

Abstract: The deep space and planetary exploration project have been acquiring more and more importance and some of them are now well established both in ESA and NASA programs. This paper presents the possibility to utilize both silicon and gallium arsenide solar cells as spacecraft primary power source for missions far from the Sun, in order to overcome the drawbacks related to the utilisation of radioisotope thermoelectric generators - such as cost, safety and social acceptance. The development of solar cells for low illumination intensity and low temperature (LILT) applications is carried out in Europe by ASE (Germany) and CISE (Italy) in the frame of an ESA programme, aimed to provide the photovoltaic generators for ROSETTA: the cometary material investigation mission scheduled for launch in 2003. The LILT cells development and testing objectives are therefore focused on the following requirements: insolation intensity as low as 0.03 Solar Constant, low temperature down to -150 C and solar flare proton environment. At this stage of development, after the completion of the technology verification tests, it has been demonstrated that suitable technologies are available for the qualification of both silicon and gallium arsenide cells and both candidates have shown conversion efficiencies over 25% at an illumination of 0.03 SC and a temperature of -150 C. In particular, when measured at those LILT conditions, the newly developed 'Hl-ETA/NR-LILT' silicon solar cells have reached a conversion efficiency of 26.3%, that is the highest value ever measured on a single junction solar cell. A large quantity of both 'Hl-ETA/NR-LILT' silicon and 'GaAs/Ge-LILT' solar cells are presently under fabrication and they will be submitted to a qualification test plan, including radiation exposure, in order to verify their applicability with respect to the mission requirements. The availability of two valid options will minimize the risk for the very ambitious scientific project. The paper describes how the technical achievements have been possible with Si and GaAs LILT solar cells (including a comparison between measured and modelled l-V characteristics) and it presents the technology verification tests results.