Measurements of radiation balance on the satellite Explorer VII

Abstract

The scientific programme of the American artificial satellite Explorer VII included an experiment on the determ~ation of the Earth’s radiation balance.* This experiment consisted in using specially constructed radiation detectors(1-3) to measure the fluxes of radiation reflected from and emitted by the Earth and also to measure the flux of direct solar radiation. The object of the experiment was to determine the large-scale fields of radiation passing out to space from those regions of the Earth’s surface and atmosphere which lay within the field of view of the detectors. In so far as the outgoing radiation is governed by the reflective and radiative properties of earthly objects (continents, oceans, clouds, expanses of snow etc.) as well as by the nature of air masses, analysis of the time and space variations of the radiation fields can in principle lead to an idea of the corresponding variations in the fields of certain meteorological elements. In particular, measurements of radiation fluxes from a satellite make it possible to analyse cloud cover associated with corresponding air masses and pressure formations and also to trace their movements in space and their variations with time. Since there are vast regions of the Earth which have been studied very little from the meteorological point of view, such information could be extremely important for weather forecasting and other practical appli~tions. The determination of variations in the fluxes of outgoing radiation on a planetary scale is also important in the study of the energetics of the atmosphere. The radiation fluxes measured in this experiment make it possible to obtain directly the space and time distribution of warm and cold pockets over the planet; these govern circulation and other dynamic processes in the atmosphere. Explorer VII was launched on 13 October 1959. Recently some of the radiation-balance measurements have been published with an interpretation from the standpoint of an analysis of the synoptic situation and cloud @-+u. It should be noted that the technique used on this satellite for measuring radiation fluxes may to some extent limit the possibilities of such an investigation. Careful selection and analysis of data recorded magnetically in the Soviet Union revealed that some were suitable for further treatment, and this was carried out on the basis of telemetric codes and calibration curves(r) published by the National Aeronautics and Space