In this paper, we address problems stemming from two different space mission projects of the CNES (French Space Agency). The first one is the Netlander mission which aims at a scientific investigation of Mars with help of probes on its surface. In the context of this mission, we are interested in both planning communications periods between Mars probes and satellites orbiting Mars, and planning experiments on probes. Linear programming and constraint propagation are developed. The second problem is in the context of the Pleiades program of Earth observing with satellites of new generation. The problem consists in selecting and scheduling images taken by one satellite in order to maximize a quality criterion depending on the acquisition rate of an image. We propose a generalized linear programming (column generation) approach for this problem.