Scientific research that requires space flight has always been subject to comparatively strong external control. Its agenda has often had to be adapted to vacillating political target specifications. Can space scientists appeal to one or the other form of the widely acknowledged principle of freedom of research in order to claim more autonomy? In this paper, the difficult question of autonomy within planned research is approached by examining three arguments that support the principle of freedom of research in differing ways. (...) Each argument has its particular strengths and limitations. Together they serve to demonstrate particular advantages of scientific autonomy, but in the case of space science, their force ultimately remains limited. However, as the arguments highlight the interrelations between scientific autonomy, the democratic process and the collective interest in scientific knowledge, they suggest that a coherent and sustained space science agenda might best be ensured by increasing the transparency of science policy decisions and involving the democratic public. (shrink)