The scientific value of research with artificial satellites

The scientific study of the upper atmosphere of the earth, the solar and lunar influences which affect its behaviour, and the immediate surroundings of the earth in interplanetary space has been proceeding for many years. This has included the investigation of pressure, density, temperature and wind distributions (atmospheric structure), the ionosphere, the airglow and aurora, atmospheric tides, magnetic variations due to circulating currents in the atmosphere or beyond, meteors, cosmic rays and solar disturbances.

In the first instance, this work was carried out exclusively by indirect methods based entirely on the use of equipment on the ground together, of course, with the maximum use of theory. Although remarkable progress has been made, there are certain properties and phenomena which cannot be studied in this way. The most important of many is the nature of the radiation from the sun before it has been modified by the atmosphere. Only a narrow spectrum range of sunlight penetrates to ground level and yet it is the absorbed radiation which is responsible for atmospheric phenomena, such as the ionosphere and the airglow. It is not only the electromagnetic radiation which needs to be studied but also the particle radiation which is responsible, for example, for auroral and magnetic storm phenomena.