New Value for the Solar Constant of Radiation

Abstract

THE solar constant of the Earth is the extraterrestrial flux of the Sun's energetic radiation integrated over all emission wavelengths and referred to one astronomical unit (AU). An accurate knowledge of this quantity and of its spectral components is an important requirement in the design of spacecraft, where the problems of maintaining the desired radiative equilibrium temperatures are especially difficult in voyages differing considerably from those of Earth-orbiting satellites. A related problem is the testing of these vehicles in space simulation systems. A joint Jet Propulsion Laboratory—Eppley Laboratory experiment is being conducted of which the basic objective is to make available a series of multichannel radiometers which have been calibrated ultimately by exposure to the Sun at altitudes above the ozonosphere (> 50 km), using the USAF/NASA X-15 rocket research aircraft, for example.