Stimulating our piece of the universe: Active experiments in space

“Life science is the only space science discipline in which space experiments are performed.” This comment was made recently at a meeting of space scientists, striking those of us in physical science disciplines as somewhat bizarre. However, I realized on further reflection that in a sense the remark was largely correct except for one area of physical science space research known as active experiments in space. Since the beginning of the space age, physical science investigators have made measurements predominantly of the space environment using advanced experimental techniques. Space experiments in this discipline have been much rarer events. Specific experiments designed to study the response of the space environment to controlled disturbances are generally termed active space experiments. In recent years the distinction between making measurements of the space environment and performing controlled experiments in that environment has been emphasized in the space physics community by a distinction in funding considerations between “Space Physics” and “Physics in Space”, that is passive versus active experimentation. However, the distinction is not always clear since even passive experiments provide some disturbance to the space environment, and some experiments use active techniques with minimal disturbance to measure ambient properties of the local or remote space environment. In this report, my intention is to address primarily those experiments which set out to actively perturb the environment from space platforms and study the effects of that perturbation.