Showing papers on "Solar constant published in 1971"

Standard Values for the Solar Constant and its Spectral Components

Abstract: Recent high-altitude aircraft, balloon and spacecraft measurements of the extraterrestrial solar irradiances indicate that the earlier integral wavelength value was too high and that the spectral data derived from ground-based techniques were uncertain. Standard values are proposed here with a summary of the supporting evidence.

The Solar Constant (A Compilation of Recent Measurements)

Abstract: A detailed compilation of the most recent values of the solar constant is given (13 values published from 1967 to 1970). The most probable value seems to be 1.95 cal cm−2 min−1 or 1.36 kW m−2 with a formal rms error of ± 0.3%. The corresponding effective temperature is 5770K. Systematic errors of the order of ± 1%, but also a possible variability of the same order cannot be excluded.

Mathematical model of the solar radiation force and torques acting on the components of a spacecraft

Abstract: General expressions for the solar radiation force and torques are derived in the vectorial form for any given reflecting surface, provided that the reflecting characteristics of the surface, as well as the value of the solar constant, are known. An appropriate choice of a spacecraft-fixed frame of reference leads to relatively simple expressions for the solar radiation forces and torques in terms of the functions of the sun-spacecraft-earth angle.

Active cavity radiometric scale, international pyrheliometric scale, and solar constant

Abstract: The active cavity radiometer type II, a new and accurate standard detector, has been developed for the absolute measurement of optical radiant flux. The active cavity radiometric scale (ACRS), defined by the active cavity radiometer (ACR), and the international pyrheliometric scale (IPS), defined by a U.S. standard angstrom pyrheliometer, have been compared in recent experiments. Simultaneous measurements of solar irradiance demonstrated an average systematic difference between the two scales of 2.2%, the measurements on the ACRS exceeding those on the IPS. An analytical study of the sensitivity of the ACR to sources of experimental error is presented. The uncertainty in the ACRS is found to be less than +--0.5% at the one solar constant level relative to the absolute scale based on fundamental physical principles. In August 1968 two ACR's measured the solar irradiance at an altitude of 25 km in a balloon-flight experiment. The solar-constant value derived from this measurement was Ho ---- 137.0 mw/cm . Scales for the measurement of radiant energy are established with respect to fundamental physical concepts by standard detectors or standard emitters of radiant energy. Establishment of a scale of radiomerry by a standard emitter usually involves the irradiance of a suitable (nonstandard) detector by a high-temperature blackbody source of thermal radiation. If the properties of the source and the charac

Solar activity and planetary luminosity

Abstract: The Chree superposition analysis of the luminosities of the planets Jupiter, Saturn, Uranus and Neptune indicates a correlation between solar activity and planetary luminosity. The variations of the solar constant in the visible range are considered to be too small to explain the observed changes in brightness. The interaction of solar extreme ultraviolet or solar wind particles with the atmospheres of these planets is probably responsible for the increased albedo during periods of high solar activity.

Solar Flux, and 'Total' Particle and O2 Density, in Upper Atmosphere

Abstract: : Solar flux, and total particle and O2 density distribution, in the upper mesosphere and lower thermosphere (70- to 150-km region) are described. Respective distributions were determined from solar flux intensities measured by ion chambers in three rocket vehicles launched on 21 February 1966 from North America (two at Eglin Gulf Test Range, Florida, and one at Fort Churchill, Manitoba). Method of determining density distributions is given. Solar flux outside and inside the absorbing atmosphere was measured for the following wave bands: 1-20A (x ray), 1140-1260A (mainly hydrogen Lyman-alpha line at 1215.6A), and 1325-1475A (Schumann-Runge continuum). Distributions of O2 and total particle density are based on the solar flux absorption in the sensible atmosphere. Results of solar flux measurements compare, in general, with results obtained elsewhere. Estimated errors vary from 10 to 100 percent. Density results also agree generally with those of other experimenters (using similar of other techniques), except for one striking difference: a step of O2 density exists at 113 plus or minus 7 km altitudes. This step, which to our knowledge has not been reported elsewhere, is described theoretically. Its existence is also confirmed by electron density data derived by ionosonde at each launch site.